SIGLENT SSA3032X input related spurious

[RFDUK]

Recently received new SSA3032X and extremely pleased with performance and would highly recommend.
Thing is the only performance issue I've found is a bit annoying and well outside Siglent input related spurious spec of -65dBC.
Am waiting on Siglent feedback response.
Wondering if anyone else has noticed this input related spurious ...
An input related spur appears 60.0MHz below the wanted input signal at -57.5dBC.
The spur appears across the whole input range to 3GHz and is very consistent.
The spur is not changed by input level from -30dBm down, that is it's always -57dBC.
No change in spur dBC with any parameter settings.
Not a show stopper for me I guess and Siglent -65dBC spec would be exceptional for a budget instrument if it met it .
Have done sanity checks with other signal sources and analyser, it's the Siglent for sure.
Wonder what other SSA3000 instruments out there do on this one?

Cheers, Martyn.

[rf-loop]

Recently received new SSA3032X and extremely pleased with performance and would highly recommend.
Thing is the only performance issue I've found is a bit annoying and well outside Siglent input related spurious spec of -65dBC.
Am waiting on Siglent feedback response.
Wondering if anyone else has noticed this input related spurious ...
An input related spur appears 60.0MHz below the wanted input signal at -57.5dBC.
The spur appears across the whole input range to 3GHz and is very consistent.
The spur is not changed by input level from -30dBm down, that is it's always -57dBC.
No change in spur dBC with any parameter settings.
Not a show stopper for me I guess and Siglent -65dBC spec would be exceptional for a budget instrument if it met it .
Have done sanity checks with other signal sources and analyser, it's the Siglent for sure.
Wonder what other SSA3000 instruments out there do on this one?

Cheers, Martyn.

Here one tiny test.
145MHz, -20dBm @ SA input port.
433MHz, -20dBm @ SA input port.
1285MHz, -20dBm @ SA input port.

SA input attenuator 10dB.  (with this and signal level -20dBm "Mixer level" is -30dBm)
Span: 200MHz
RBW=VBW=1kHz
Sweep type: FFT
Detector: Pos Peak Average mode Log Power
In every picture there can see 60MHz LSB spur. (with 435MHz center freq, spur is not always exactly 60MHz as can see in 433MHz image)

Signal source. HP8642B
Cable between HP and SA   3m  Suhner Sucoflex 104/PEA.

In all these example cases this "60MHz below carrier spur" level is under -70dBc.


145MHz


433MHz


1285MHz

[RFDUK]

Thanks very much for your tests rf-loop, that's very helpful. Now I can see the instrument is capable of meeting specification on that spur.

Here are plots of the SA here to compare to yours. I noticed the noise floor on your plots is slightly better than this one too.

Signal source HP 8657B.

I wonder how old your instrument is and the hardware version?
My HW is 07.03.00. Manufacture October 2017.

I'll talk to the supplier Batronix in Germany about the issue, although I notice the lead time on new instruments has extended into next year due to the current promotion offers.

Many thanks for your help, best regards from the UK, Martyn.

[rf-loop]

I wonder how old your instrument is and the hardware version?
My HW is 07.03.00. Manufacture October 2017.

My HW is 07.03.00. Manufacture May 2016.

[adamgreig]

My 2017-06 model (same HW 07.03.00) also comes in just around -70dBc and with a similar noise floor to rf-loop. Same settings, but 100M carrier.

[RFDUK]

Many thanks for the test result.

Looks like I need a replacement instrument.

[G0HZU]

This can happen on the old classic lab analysers too. I spotted this thread a couple of years ago on the Keysight forum

https://community.keysight.com/thread/5220

You can see there are some pretty ropey HP8568 analysers out there too. I suspect that these analysers have been fiddled with inside over the years or maybe something has aged. But the -10.7MHz spur on these HP8568 analysers looks really grim. I suspect that this is an issue to do with the alignment of the second IF stage on the HP8568.

If you look at the thread, I posted up the same settings using my analyser and it was OK. When zoomed in on a narrow RBW I think my analyser showed the -10.7MHz spur at -86dBc. I know the history of mine from new. I first started using it in about 1990. It was donated new/free to the company by a customer on a long term project. I then bought it from the company about 10 years or so ago. So it is a good example I think.

[G0HZU]

Not a show stopper for me I guess and Siglent -65dBC spec would be exceptional for a budget instrument if it met it .

If it's any consolation, I tested a Tektronix RSA306 spectrum analyser a while back. I was given an official Tek RSA306 eval model with all its test accessories for a few hours to take home from my works company to evaluate. I think Tek claimed better then -50dBc spurious in the glossy brochure for this analyser.

But within a few hours of reverse engineering its frequency plan (modelled on a computer for every tuned frequency at various span settings) I predicted places the spurious could be as bad as -9dBc. Yes, just -9dBc and this was proven with a few tests at specific frequencies and span settings. It really was this bad. I then used the computer model to try and find (user) frequency and span combinations that had lots of spurious and it was easy to find FOUR spurious on the display that were out of spec in just one single span setting. I think this was one at -9dBc two at -15dBc and one at -30dBc but I can't remember for sure.

It was really poor and I think Tek changed the frequency plan in the firmware because of this. I've not had access to a revised version to play with. We didn't buy any Tek RSA306 portable analysers after my eval work.

[RFDUK]

Thanks G0HZU, your observations on the older boxes is interesting.
I remember using a TEK 2710 35 years ago which was easily the worst example of a spectrum analyser I've come across in that price range over 40 years.
The HP 8568A input related spurious specification was better than -75dBC for -40dBm at the first mixer.

The Siglent -60MHz spur is constantly present at any input frequency 60MHz through 3 GHz, so is a bit annoying.

On the plus side it is a consistent offset to the input signal, so easily recognised. It's a problem though if we are presenting a plot to a customer and have to explain an internally generated spur at what is a modest -57dBC. Siglent claim -65dBC and it would be nice to have a typical <-70dBC on a professional instrument, for a spur that's constantly present. Thanks to the other posters that demonstarted that -70dBC is indeed typical for the Siglent. That's really nice performance in this price range.

Looks like mine is faulty. It's well out of spec but thanks to the supplier Batronix Germany who arranged return shipping for me, full marks to them and it's now on it's way back and I'm waiting on a new instrument.

No hesitation in highly recommending the Siglent SSA3000 analysers. Except for this issue I found the performance and ergonomics to be excellent in all respects. It's a bit worrying it got through Final Functional Testing at the factory, then again something could have happened in transit.

[rf-loop]

Thanks G0HZU, your observations on the older boxes is interesting.
I remember using a TEK 2710 35 years ago which was easily the worst example of a spectrum analyser I've come across in that price range over 40 years.
The HP 8568A input related spurious specification was better than -75dBC for -40dBm at the first mixer.

The Siglent -60MHz spur is constantly present at any input frequency 60MHz through 3 GHz, so is a bit annoying.

On the plus side it is a consistent offset to the input signal, so easily recognised. It's a problem though if we are presenting a plot to a customer and have to explain an internally generated spur at what is a modest -57dBC. Siglent claim -65dBC and it would be nice to have a typical <-70dBC on a professional instrument, for a spur that's constantly present. Thanks to the other posters that demonstarted that -70dBC is indeed typical for the Siglent. That's really nice performance in this price range.

Looks like mine is faulty. It's well out of spec but thanks to the supplier Batronix Germany who arranged return shipping for me, full marks to them and it's now on it's way back and I'm waiting on a new instrument.

No hesitation in highly recommending the Siglent SSA3000 analysers. Except for this issue I found the performance and ergonomics to be excellent in all respects. It's a bit worrying it got through Final Functional Testing at the factory, then again something could have happened in transit.

My opinion is that your unit have problem. It is far out from specifications. Over 7dB out from specifications limit. And just this specification is not labeled as "typical" like some other specifications. It reads exactly:

Input related spurious:
Mixer level = -30 dBm, 20 ? to 30 ? <-65 dBc

Also your SA show bit high base noise level but this may be normal variation between individual units but more like higher side. Base noise can be different in individual SA's but still it is bit high and also in same SA  clearly out of specs spur level - so:  My own personal opinion is that right address for this SA is Siglent service.

[RFDUK]

Yes, thanks to the posts I can see the noise floor is suspiciously higher than two other units manufactured over a year apart, so not a good sign either.

I was happy to discover the spurious specification was fully warranted and not 'typical' or 'nominal'.

I'll post some test results on the new one when it arrives, estimated in 3 or 4 weeks.

I only had a week or two with this instrument but missing it already. All other analysers here are not so easily portable and cause me back pain when removing from the bench stack!

[RFDUK]

New SSA3032X arrived (manufactured NOV) and unfortunately the input related spur at -60MHz is worse than the first unit.
Siglent warranted spec is better than -65dBC.
First instrument did -57dBC.
The second instrument is doing -51dBC.
The spur is always there 60MHz below the input signal and at -51dBC is a show stopper unfortunately.
We really love this instrument otherwise.

I'm taking this up with Siglent through Batronix (Germany) our supplier and will post whatever develops.

I would appreciate if anyone with a recently purchased (NOV/DEC 2017) SSA3032X instrument would post what they see on the spur at 60MHz below the input signal?

[Performa01]

New SSA3032X arrived (manufactured NOV) and unfortunately the input related spur at -60MHz is worse than the first unit.
Siglent warranted spec is better than -65dBC.
First instrument did -57dBC.
The second instrument is doing -51dBC.
The spur is always there 60MHz below the input signal and at -51dBC is a show stopper unfortunately.
We really love this instrument otherwise.

I'm taking this up with Siglent through Batronix (Germany) our supplier and will post whatever develops.

I would appreciate if anyone with a recently purchased (NOV/DEC 2017) SSA3032X instrument would post what they see on the spur at 60MHz below the input signal?

Following my recommendation, a friend of mine purchased such an instrument quite recently (also from Batronix).

Now I have asked him to perform a quick test and sure enough, the results are quite similar to what you’ve got with your first machine.


SSA_171231003124

It is only marginally better at -58.7dBc and certainly far out of spec.
The elevated noise level is also there, even though this appears to be still within specs.

Now let’s wait and see how Siglent will handle this incident, fingers crossed…

[TurboTom]

These are really some funny spurs -- they appear to be some kind of second order mirror product. Since I'm lucky to own an older version of the SSA, the spur is present at around -71dBc. A closer look and some small variations of the input frequency show that the spur moves in the opposite direction of the input frequency. It seems to appear in a window round about 59...61MHz below the input frequency and tends to move at twice its rate (relatively to it). On my SSA, there are certain input frequency settings that produce no observalbe spur, for example 147MHz. When the spur leaves the window at one end, a new one appears at the other.

Since the higher level of these spurs and the overall slightly increased noise level appears to be common for the recently built instruments, who knows if Siglent tried to cut cost by changing some details about IF filtering, maybe just eliminated one of the two NDF8027SAW filters... Without a teardown of one of the more recent units, we'll probably never know  . Of course i wouldn't recommend to do this, Those who got one of the instruments that are out of spec should plainly return them and have them replaced with something that meets the specs (...if available...).

Cheers & Happy New Year,
Thomas

[cncjerry]

Setting aside the obvious Siglent issue, I remember reading somewhere how to test if an observed signal was a spur or input related. In the case of the Siglent, it is very replicable at 60Mhz below so it's not like you would go try to fix your DUT the next time you see it.  Anyone remember how to test for spurs?

Interesting thing here is that I have strong FM broadcasts all around 100Mhz so I really couldn't do much testing around that frequency.  But I noticed yesterday after moving my lab down a floor with two walls that have slopiing soil levels outside that this is no longer an issue.  Prior to the move I had broadcasts at 97.3 and 107.1Mhz that were huge, even ruined the 1Khz test signals on my scopes.

[RFDUK]

Thank you very much for posting the plot Performa01 and to your friend, that's really useful. I've boxed up my second instrument and now waiting on Batronix to discuss the issue with Siglent.

Thanks for your observations Thomas, I hadn't looked that closely. Yes, I see that behaviour too on the second instrument. At some input frequencies I can see multiple spurs a couple of MHz apart, centred on a -60MHz offset.

I hope Siglent have a fix deliverable in a reasonable timeframe. I'm now into the third month following our initial order, so it's very troublesome for sure. I'll keep this thread up to date with my news from Batronix.

Best wishes for the New Year,
Martyn.

[tautech]

 
This must be very setting specific.

Source: HP 500 MHz analog sig gen.
70 MHz @ -60 dBm
Connection N-N Cable Siglent N-N-6L (6 GHz)


SSA3032X demo unit 1yr+ old.



145 MHz @ -60 dBm
Brand new SSA3021X Cal date 24 Nov 17
You can see the 1st harmonic @ 289.6 MHz but nothing else. NO sign of 60 MHz spurs.
What settings must I use to find them ?



As you can see my 3.2 GHz unit has a slightly lower noise floor with these settings.

[RFDUK]

Hello tautech, many thanks for posting. It will be good to see the comparison between the two instruments.

Unfortunately it's not setting specific, you need an input to noise floor range large enough to see the spur.

The Siglent spec is better than -65dBC, so you need at least 65dB of display range below your input signal to the noise floor.

If you input a wanted -20dBm signal, the input attenuation and RBW need setting to display a noise floor of -85dBm or lower, otherwise the out of spec spur is in the noise.

The spur is at -60MHz, so wanted inputs below 60MHz don't bring up this spur. You need to test with a wanted input above 60MHz.

It may be useful to use the instrument setups shown in the plots earlier in the thread.

Look forward to seeing your results, that would be great. Cheers, Martyn.

[nugglix]

Also an older model (mid sept. 2016, liberated).
100MHz Sine from my SDG2042X 

Looks much better than the newer models, but the spur is still very obvious.

[RFDUK]

Thanks nugglix, it confirms the older ones a coming out consistently 5dB inside spec.

[rf-loop]

Also an older model (mid sept. 2016, liberated).
100MHz Sine from my SDG2042X 

Looks much better than the newer models, but the spur is still very obvious.

Well inside specifications. (< -65dBc)  What is quite good in this class of equipments.

But these some example units here what show nearly around -50dBc spurious levels, they can not accept at all because they totally break specifications like default units. Some things are wrong there - and badly.


Also note that your test setup mixer level is -20dBm.

Input related spurious are specified using mixer level -30dBm.  For comparable measurements it is better to use it even if it affect more or less in different situations.

[tautech]

We can go witch hunting spurs all year. 
Still nothing at 60 MHz in either SSA.

FOI ~145 MHz @ -30 dBm

[nctnico]

Hint: 144.7-85.33=59.37

[RFDUK]

Thanks for that. The problem spur is at approximately 60MHz below the wanted input, not at '60MHz'.

Your spur is there, 60MHz below your wanted 2m signal. The signal at 85.333MHz isn't real, it's the analyser. It's at -70dBC like all the other older instruments posted. That's nicely in spec and fine.

I wish mine was! The second instrument here shows -51dBC. That's almost 20dB worse than your plot.

This is serious stuff, not a witch hunt I'm afraid. -51dBC on an input related spurious relegates a spectrum analyser to 'toy' status really. Particularly since it's ever present throughout the whole spectrum up to 3.2GHz.

Wonder what your new one looks like?

[RFDUK]

An additional observation that I perhaps didn't make very clear earlier in the thread ...

Input related spurious are typically troublesome at higher input levels when nonlinearities rear their heads.

The Siglent spec of better than -65dBC is for levels of -30dBm at the input mixer and lower. That's a decent enough spec to have.

The mechanism for this -60MHz spur isn't nonlinearity at all though.

At input levels of -30dBm (or even -20dBm for that matter) and anything lower, the spur dBC is completely linear to the input signal.

The problem is purely a mixing product and filter issue.

[nugglix]

To make clear that the spurs are relative to the input signals I traced 2 signals, 2 MHz apart.

-20dBm signal levels, 10dB attenuator setting.

One can clearly see the 2 spurs and they're at the same ~ -70dBc level as before.

Done w/ the same SDG2042X as above, just using the channel combination feature.


PS: No witches involved, this is a witch free household.


Edit: yes, played w/ signal levels a bit and the spur behaves completely linear to the input signal strength.
Edit2: remove - before attenuator setting.

[Performa01]

FOI ~145 MHz @ -30 dBm

It’s interesting to see the spectrum above the carrier for once. As it seems, there is another spur at almost exactly 200MHz above the carrier, at a similar level of ~-70dBc.

Did anyone else see such a spur on their instrument and what’s its level on the new units?

[RFDUK]

Here is the second (NOV manufacture) unit on a wider span.

All's well above the wanted to better than -70dBC.

BUT at -60MHz -50dBC!

[G0HZU]

I remember looking at the teardown for this analyser and I think the ADC samples at 40Msps. So it would make sense if the final IF (IF3) was centred on 30MHz especially if the 810MHz IF2 SAW filter is as selective as the datasheet suggests. The teardown showed two 810MHz SAW filters in series and so the image rejection at a 60MHz offset should be really good here according to the datasheet response.

But this assumes that the final IF really is 30MHz. It could be 50MHz or 70MHz or even higher. If it was 30MHz then I guess that the first IF would be 3930MHz, the second IF 810MHz. LO2 would be 3120MHz and LO3 would be 3120/4 = 780MHz.

This would give a strong image response at -60MHz if there was something wrong with the filtering at the two 810MHz SAW filters at IF2? But all this is a guess. I don't know what the correct frequency plan for this analyser is. However, it should be possible to go sniffing with another analyser for the LO1, LO2 and LO3 frequencies... maybe hold a tiny loop probe (5mm dia loop across the end of some coax?) near the analyser input or the case. You would probably need a preamp and a narrow span and narrow RBW on the sniffing analyser and you would have to set the Siglent to a narrow span of <<1MHz to keep the LO1 in one place.

[Performa01]

I remember looking at the teardown for this analyser and I think the ADC samples at 40Msps. So it would make sense if the final IF (IF3) was centred on 30MHz especially if the 810MHz IF2 SAW filter is as selective as the datasheet suggests. The teardown showed two 810MHz SAW filters in series and so the image rejection at a 60MHz offset should be really good here according to the datasheet response.

But this assumes that the final IF really is 30MHz. It could be 50MHz or 70MHz or even higher. If it was 30MHz then I guess that the first IF would be 3930MHz, the second IF 810MHz. LO2 would be 3120MHz and LO3 would be 3120/4 = 780MHz.

This would give a strong image response at -60MHz if there was something wrong with the filtering at the two 810MHz SAW filters at IF2? But all this is a guess. I don't know what the correct frequency plan for this analyser is. However, it should be possible to go sniffing with another analyser for the LO1, LO2 and LO3 frequencies... maybe hold a tiny loop probe (5mm dia loop across the end of some coax?) near the analyser input or the case. You would probably need a preamp and a narrow span and narrow RBW on the sniffing analyser and you would have to set the Siglent to a narrow span of <<1MHz to keep the LO1 in one place.

That’s what I would have liked to do – estimating the frequency plan and speculating about the source of this spurious response, but to be honest, I just didn’t feel like watching the teardown again and finding the threads where this has been discussed back then, in order to get the required information. So I’d like to say many thanks to you for your analysis!

Yes, one could verify your assumptions by doing the measurements as you’ve suggested. Not many will have another appropriate instrument to do this though, I’m afraid. Moreover, all the ones who have discovered that their recently purchased SSA3kX has this flaw will most likely be very reluctant to open it up, but rather plan to send it back for repair or replacement…

[RFDUK]

Thanks very much G0HZU, I went in search of architecture and frequency info while the first instrument was here but only found the one hi res photo of the PCB.

I did connect a high gain preamp to HP 8596E and looked at the leakage on the TG and RF in ports several weeks ago. Found the 1st LO leakage on the TG port, TG off, if I remember correctly. It was at a very low level, so full marks to Siglent there. I didn't manage to work anything out and gave up.

Thanks for your speculation on the frequency plan. I'll try your suggestion of using a pickup loop with the preamps.

Someone speculated they may have cost engineered one SAW filter out and looking at the SAW filter data the -50dBC spur performance I see would fit that. One SAW filter is probably only some 10s of pence so unlikey when the -65dBC specification is not going to be met on paper. Perhaps it's a change of SAW filter manufacturer on the BOM that's caught them out.

I'll post LO activity details seen with a probe.

[RFDUK]

There's lots of case radiation to see to several GHz with a probe, presumably PLL products.

I searched for the final LO specifically and the most prominent clean narrowband signal I found was 750.000MHz. This one is quite loud.

Looked at the conducted ports again. The RF input is the most fruitful. Two components observed as follows, SA zero span ...

(Centre f) ... Sig 1 ... Sig 2
(100MHz) ... 915 ... 2025
(200MHz) ... 1013 ... 2070
(1000MHz) ... 1815 ... 2475

The frequencies are approximate since recorded from a broad span.

If the observed 750MHz is the final LO, final IF is 60MHz. Does the -60MHz spur fit that? ... it's not immediately obvious to me but I'll have a ponder on the possible mechanism.

[Performa01]

There's lots of case radiation to see to several GHz with a probe, presumably PLL products.

I searched for the final LO specifically and the most prominent clean narrowband signal I found was 750.000MHz. This one is quite loud.

Looked at the conducted ports again. The RF input is the most fruitful. Two components observed as follows, SA zero span ...

(Centre f) ... Sig 1 ... Sig 2
(100MHz) ... 915 ... 2025
(200MHz) ... 1013 ... 2070
(1000MHz) ... 1815 ... 2475

The frequencies are approximate since recorded from a broad span.

If the observed 750MHz is the final LO, final IF is 60MHz. Does the -60MHz spur fit that? ... it's not immediately obvious to me but I'll have a ponder on the possible mechanism.

Here are my thoughts so far (bear in mind, I’m not very experienced in defining frequency plans for triple conversion receivers, but anyway):

We do not know the first IF, nor the 3rd, but we do know the 2nd to be 810MHz.

The first IF has to be above the highest input frequency, so I’d say it has to be at the very least 3.6GHz (hopefully a good deal higher than that).

To me it’s quite obvious the problem cannot be in the first mixer, if only because the spur has a fairly constant offset to the input signal (within 2MHz) and is present for the entire input frequency range. Any unwanted mixer product would only fall within the first IF for a very narrow range of input frequencies. Furthermore, I would rule out that it’s a mixing product with any harmonic of the input signal, as various different signal sources have been used with quite similar results, and the HP8642B used by rf-loop has provided a decent spur suppression even though this RF-generator of all things exhibits rather high harmonic distortion.

So let’s look at the 2nd mixer.
We have to make an assumption for the first IF and this is important, as this determines the 2nd LO frequency and the spurious mixer products in turn.

Since we obviously want the 3rd LO to be easily derived from the 2nd LO, it should indeed be a 4:1 ratio as suggested by G0HZU and we need to consider the 3rd IF at this point as well.

And here the troubles start. A 3rd IF of 30MHz could explain an unwanted image response, but that’s not what we’re seeing here. It rather looks like the spurious frequency moves twice as fast as the signal frequency, hence it has to be a 3rd (or 4th?) order intermodulation product, so the 3rd IF could be anything but 30MHz and 60MHz would be rather plausible.

Also, with the frequency plan posted by G0HZU, we’d never get out of the reverse frequency position of the IF signal, but that does not change with IF frequency, we would rather have to give up the 4:1 ratio for the 2nd and 3rd LO.

Having played with the numbers a bit (unfortunately I don’t have any fancy software for that), I just didn’t find a solution yet. Independent of your measurements, I’ve landed at 60MHz IF3 and 750MHz LO3 at some point, but still didn’t get anywhere. Because of the symptoms, I firmly believe that it has to be some unwanted mixing product with the 2nd harmonic of the 2nd IF signal. A 4th order mixing product looks good at first glance, but then I believe the spur would appear 30MHz off the carrier and not 60MHz.

In any case I am still puzzled and would not rule out that it’s not a problem with the 2nd IF filter, but maybe the 3rd mixer. Maybe they have used a double balanced mixer initially and thought they swap it out for a single diode – LOL. Just kidding…

[Bicurico]

Hi,

Out of curiosity I used my "VMA Simple Spectrum Analyzer" software with the 35MHz-4.4GHz SMA device and reproduced the same settings as in the first post of this thread.

Attached is the result. Mine is of the older SSA3021X.

Regards,
Vitor

[G0HZU]

Performa01: And here the troubles start. A 3rd IF of 30MHz could explain an unwanted image response, but that’s not what we’re seeing here. It rather looks like the spurious frequency moves twice as fast as the signal frequency, hence it has to be a 3rd (or 4th?) order intermodulation product

Don't forget that the analyser is running in an FFT mode so the span you see on the display isn't a linear sweep with a fixed IF of (say) 30MHz with a 1kHz 'digital' RBW. It's a patchwork of FFTs maybe 2MHz wide made up of thousands of FFT bins. The first LO will step in fixed steps as each FFT is taken across the sweep. This means that the image offset will be a function of the offset from the centre of each FFT. So the spur won't always appear 'exactly' at a 60MHz offset. However it will be close to 60MHz and can be expected to wrap around inside a window of a few MHz. A bit like TurboTom described in post #13?

We do not know the first IF, nor the 3rd, but we do know the 2nd to be 810MHz.

We don't even know if the IF2 is 810MHz for certain. It could be 812MHz or 814MHz for example. They might run the IF at a slight offset to the centre frequency of the 810MHz SAW filter. Also, I've only got a few images of the main board to work with and I'm guessing that the ADC samples at 40MHz. But it might sample at some other frequency and this would throw off all my guesstimates

(Centre f) Sig 2
(100MHz)  2025
(200MHz)  2070
(1000MHz) 2475

The LO1 synthesiser uses a doubler so double these numbers and you get:

(Centre f) Sig 2  (difference =IF1?)
(100MHz)  4050     3950MHz
(200MHz)  4140   3940MHz
(1000MHz) 4950   3950MHz

So the first IF could be close to 3950MHz. Can you zoom in on the 2025MHz signal (at CF 100MHz) and measure it more accurately?

[G0HZU]

(Centre f) ... Sig 1 ... Sig 2
(100MHz) ... 915 ... 2025
(200MHz) ... 1013 ... 2070
(1000MHz) ... 1815 ... 2475

(2025 * 2) - 915 = 3135MHz = LO2?
(2070 * 2) - 1013 = 3127MHz = LO2?
(2475 * 2) - 1815 = 3135MHz = LO2?


It's worth measuring all these frequencies accurately so we can get closer to the frequency plan. Note that they will probably shift the first IF in subtle ways to avoid major internal spurious terms.
So IF1 probably won't be fixed and this means that IF2 won't be fixed inside the 810MHz SAW filter. It could vary depending on the analyser frequency. They could be shifting/sidestepping the IF frequency several MHz to avoid internal (nLO1 +/- mLO2 +/- xLO3 = IF3) spurious terms on certain frequencies.

[rf-loop]

Hi,

Out of curiosity I used my "VMA Simple Spectrum Analyzer" software with the 35MHz-4.4GHz SMA device and reproduced the same settings as in the first post of this thread.

Attached is the result. Mine is of the older SSA3021X.

Regards,
Vitor

Where from this enormous shocking noise level is coming from.  I belive this around -60MHz spur is still there but your  noise covers it totally (because your spur level is inside specs. Also your test signal carrier level is bit low from -30dBm mixer level).

[RFDUK]

Thanks for all the input, very interesting.

I measured what must be the 1st LO more accurately ...
(100MHz) ... 2.015 x 2 = 4.03
(200MHz) ... 2.065 x 2 = 4.13
(1000MHz) ... 2.465 x 2 = 4.93

So confirmation of a 3930MHz 1st IF

[RFDUK]

I'm thinking the 750MHz I saw on the pick up loop wasn't 3rd LO after all ...

1st IF is 3930MHz.
2nd LO is 3120MHz.
3rd LO is 780MHz.
3rd IF is 30MHz.

[G0HZU]

If I had to guess what was 'wrong' with the analysers affected with this problem I would include the possibility that there is inconsistency in the way the big aluminium metalwork screen 'fits' to the PCB.
If the metalwork mating surface has highspots on it or maybe some contamination then this can mean the metalwork can become a leakage path rather than just a screen. Or maybe there needs to be some RF absorber here inside the metalwork pocket above the SAW filters?

If there is a leakage path that can bypass the SAW filters (via the metalwork) then the effective performance of the two cascaded SAW filters can be ruined very easily and you could easily get the problem as per the image below. The green trace might represent the full potential of the two filters but the red trace could represent what happens with a leakage path.

This would only have an IF3 image rejection of 55dB for example.

[RFDUK]

Yes, cascaded SAW filters looking for >70dB stop band could be a bit touchy.

I have a test that is quite convincing on the 3rd LO frequency determination ...

Using a sensitive comms receiver with SSB demod tuned to 780MHz, firstly with quarter wave whip placed around the case of the SSA. I heard a clean carrier but also noted carriers at 10MHz intervals above and below.

I connected the comms RX directly to the SSA RF input and only hear the 780MHz and at reasonable strength too.

[Performa01]

Where from this enormous shocking noise level is coming from.

Maybe from ref. level = 0dBm and attenuator = 20dB? (hint, hint, for Bicurico )

[Performa01]

Performa01: And here the troubles start. A 3rd IF of 30MHz could explain an unwanted image response, but that’s not what we’re seeing here. It rather looks like the spurious frequency moves twice as fast as the signal frequency, hence it has to be a 3rd (or 4th?) order intermodulation product

Don't forget that the analyser is running in an FFT mode so the span you see on the display isn't a linear sweep with a fixed IF of (say) 30MHz with a 1kHz 'digital' RBW. It's a patchwork of FFTs maybe 2MHz wide made up of thousands of FFT bins. The first LO will step in fixed steps as each FFT is taken across the sweep. This means that the image offset will be a function of the offset from the centre of each FFT. So the spur won't always appear 'exactly' at a 60MHz offset. However it will be close to 60MHz and can be expected to wrap around inside a window of a few MHz. A bit like TurboTom described in post #13?

We do not know the first IF, nor the 3rd, but we do know the 2nd to be 810MHz.

We don't even know if the IF2 is 810MHz for certain. It could be 812MHz or 814MHz for example. They might run the IF at a slight offset to the centre frequency of the 810MHz SAW filter. Also, I've only got a few images of the main board to work with and I'm guessing that the ADC samples at 40MHz. But it might sample at some other frequency and this would throw off all my guesstimates

I should have taken all this into account - but I got carried away quite obviously. Thank you for pointing this out and tossing me back on track!

With these modern processor controlled equipment it's really hard to tell what's actually going on inside...

[Performa01]

If there is a leakage path that can bypass the SAW filters (via the metalwork) then the effective performance of the two cascaded SAW filters can be ruined very easily and you could easily get the problem as per the image below. The green trace might represent the full potential of the two filters but the red trace could represent what happens with a leakage path.

It really is mazing to see what fancy tools RF professionals have at their disposal nowadays!

[G0HZU]

This may be a bit off topic, but when I looked at the teardown pictures I also spotted the IF3 bandpass filter on the PCB and this lumped LC filter appears to use a fairly classic 'symmetry preserving' topology. Dave's closeup images show the value of most of the inductors so I was able to reverse engineer the probable response of this filter. Obviously, I can't tell what the capacitor values are but I can get some idea from the colour of the dielectric which ones are below about 200pF. I also had to use fixed capacitor values and fixed inductors so this made it easier to guess the filter components.

This filter has to be symmetrical because it has alias terms to reject either side of it and that is why it uses this odd looking topology. See below for my first crude attempt at predicting the response assuming it really is a 30MHz IF at IF3. Because I know the inductor values and I have experience designing filters with this topology I can guess the values of the caps fairly well. But I could still be very wrong here!

Assuming I've got close to the actual design values you can see that the designer was aiming for over 80dB alias rejection ahead of the ADC. The 810MHz SAW filter effectively helps a bit here too. I've drawn the alias responses by hand in purple at about -80dBc.

Note that I've swapped around the order of the series L and C components in my CAD version but this is because this is the way they get produced in my synthesis/optimiser tool. But it will not affect the response.

[G0HZU]

If you look at Dave's image of the PCB in the post above you can see there are a lot of 'no fit' SMD parts on the PCB around this IF3 BPF. It looks like the designer considered having several switched IF3 bandpass filters. This could have meant several 30MHz filters with different bandwidths could have been fitted (selected in firmware?) or maybe an alternative filter at the 50MHz alias to act as a spurious cancelling option for certain types of internal spurious terms. But for whatever reason, these parts were not fitted to the PCB. Maybe this was for cost or maybe the selection switches had limited isolation and spoiled the performance in some way.

Just below the yellowed outline of IF3 in the PCB image are the two 810MHz SAW filters. They live in a tiny pocket (circled in blue below) but maybe the grounding to the metalwork is not good here? The lid/screen screws are a fair way away from this pocket and there is an isolation slot cut into the PCB here as well. So they were obviously trying for isolation here but maybe it isn't repeatable with the metalwork? So signals can bypass the SAW filters and get into the (ADE-2) third mixer?

[Bicurico]

Where from this enormous shocking noise level is coming from.

Maybe from ref. level = 0dBm and attenuator = 20dB? (hint, hint, for Bicurico )

Yes, I overlooked that...

Here the same screenshot, but with Attenuator = 0dB.

Regards,
Vitor

EDIT: Changed picture with exactly the same settings as RFLoop's first post.

[RFDUK]

Where from this enormous shocking noise level is coming from.

Maybe from ref. level = 0dBm and attenuator = 20dB? (hint, hint, for Bicurico )

Yes, I overlooked that...

Here the same screenshot, but with Attenuator = 0dB.

Regards,
Vitor

EDIT: Changed picture with exactly the same settings as RFLoop's first post.

Hello Vitor,

Yes that's fine, very similar to other older instruments and nearly 3dB inside Siglent specification.

Regards, Martyn.

[Performa01]

Here the same screenshot, but with Attenuator = 0dB.

Regards,
Vitor

EDIT: Changed picture with exactly the same settings as RFLoop's first post.

Almost there … this test was meant to be performed with a -30dBm mixer input level. So in order to have a completely comparable result, you should either lower the signal level to -30dB or set the attenuator to 10dB.

On the other hand, current hypothesis states that the spurious response 60MHz below the input signal is not a distortion product, but some sort of image response, so it might not make a difference.

Anyway, we can see lots of spurs here, but that might just be the signal source.
The relevant spur at 85MHz is only some -62dBc, so your instrument might  be slightly out of spec. as well.

To be sure about that, please add 10dB attenuation and repeat this very test.

Oh – you have changed settings while I wrote the above post. Still not completely there though, as the signal level should be -30dBm at the mixer input and that means you need a -20dBm signal with 10dB attenuator. Your signal level appears to be about -14dBm.

Still interesting to see that the spurious response is within specs now.

This would be a hint that it might be a distortion product after all!

EDIT: aah - and all the other spurs have vanished in the new screenshot, so the analyser was indeed overloaded at the first test.

[Bicurico]

Have patience with me... it was early in the morni by and I had little time to grab the pictures, before going to work...

Cheers,
Vitor

[RFDUK]

Our second faulty SSA3032X returned under warranty to Germany today.

Now 9 weeks from initial purchase, but we like this instrument, so waiting on a replacement ... third time lucky? Hope so.

[Performa01]

Our second faulty SSA3032X returned under warranty to Germany today.

Now 9 weeks from initial purchase, but we like this instrument, so waiting on a replacement ... third time lucky? Hope so.

Fingers crossed!

In a situation like this, at least by now, a good distributor should test any new instrument for this specific flaw before sending it to you (or anyone else for that matter). Have you negotiated something like this?

[RFDUK]

Our second faulty SSA3032X returned under warranty to Germany today.

Now 9 weeks from initial purchase, but we like this instrument, so waiting on a replacement ... third time lucky? Hope so.

Fingers crossed!

In a situation like this, at least by now, a good distributor should test any new instrument for this specific flaw before sending it to you (or anyone else for that matter). Have you negotiated something like this?

I'm working on the assumption that Batronix forwarded the 2nd instrument to me on the basis the 1st was an isolated failure. The 1st replacement unit I assume was not checked in Europe, it looked sealed from the factory.

When I received a second instrument with the same fault, I suggested to Batronix that Siglent had a problem in production. That was on Dec 28th.

What I've asked for on the 28th Dec ... Batronix to establish a dialogue with Siglent to confirm they know of the issue and give us confidence they can deliver an instrument in specification in a reasonable timeframe? They agreed to do this.

I'm optimistic if Batronix live up to their customer service claims we are now on a fast track to progress. I'll let you know.

[rf-loop]

Here is some things about  60MHz below carrier spur.

Here is case when carier moves slowly up.
If slowly move carrier frequency up this spur move down until it hop up 2.5MHz. After jump up it again continue down until it have moved 1.25MHz  and again hop up (if carrier continue moving up).
It moves like zig-zag.  Moves slowly down same amount what carrier moves up. Until it reach limit where it need hop up.

These movements are roughly (not measured enough accurately) 1.25MHz down following carrier but opposite direction, and  then 2.5MHz hop and again start moving down following carrier but opposite direction.

I have not opened my SSA for look what happen if take bottom and top aluminium block out and try do some GND contackt-seal trick for reduce possible leak between blocks.  Area between IF3 and 810MHz saw filter looks "terrible" if think high grade isolation but I have not opened it for look aluminium wall between these blocks. Also between these blocks GND is cutted for air gap but....  is it possible also that this aluminium block do some "fun" things and then every SA is different. I dso not like idea that there is just plain aluminium surface "contacting" (or not) with PCB GND surface "randomly" here and there and mostly just near screws (if they are tightened right. But how can tighten chinese soft screws... 
In professional equipments there is mostly also good flexible rf-seal in this kind of places between aluminium blocks and PCB.

Attached images may clarify how this spur frequency acts relative to carrier frequency.
Note that for this 10MHz span 60MHz image I have rised 120MHz carrier level so that spur level rise for better visibility.
Other image show same carrier but now with -30dBm mixer level and there can see spur is under -70dBc.

[Orange]

Here is some things about  60MHz below carrier spur.

Here is case when carier moves slowly up.
If slowly move carrier frequency up this spur move down until it hop up 2.5MHz. After jump up it again continue down until it have moved 1.25MHz  and again hop up (if carrier continue moving up).
It moves like zig-zag.  Moves slowly down same amount what carrier moves up. Until it reach limit where it need hop up.

These movements are roughly (not measured enough accurately) 1.25MHz down following carrier but opposite direction, and  then 2.5MHz hop and again start moving down following carrier but opposite direction.

I have not opened my SSA for look what happen if take bottom and top aluminium block out and try do some GND contackt-seal trick for reduce possible leak between blocks.  Area between IF3 and 810MHz saw filter looks "terrible" if think high grade isolation but I have not opened it for look aluminium wall between these blocks. Also between these blocks GND is cutted for air gap but....  is it possible also that this aluminium block do some "fun" things and then every SA is different. I dso not like idea that there is just plain aluminium surface "contacting" (or not) with PCB GND surface "randomly" here and there and mostly just near screws (if they are tightened right. But how can tighten chinese soft screws... 
In professional equipments there is mostly also good flexible rf-seal in this kind of places between aluminium blocks and PCB.

Attached images may clarify how this spur frequency acts relative to carrier frequency.
Note that for this 10MHz span 60MHz image I have rised 120MHz carrier level so that spur level rise for better visibility.
Other image show same carrier but now with -30dBm mixer level and there can see spur is under -70dBc.

I think the frequency hopping is due to the fact that the analyzer does the analysis based on an FFT. If FFT is involved the LO probably is set at fixed intervals.
You can try and deselect FFT, and see if the frequency hopping still occurs...

[G0HZU]

I really don't think anyone should take their analyser apart yet but if anyone is brave enough to take their analyser apart then please be VERY careful not to flex the big PCB because you could easily cause cracks inside the many ceramic SMD caps on the main board. Even a tiny amount of flex/stress could damage lots of capacitors. Not good!

We don't know what is causing the variability in rejection. It could be they changed something on the PCB or it could be a metalwork/isolation issue. It could just be bad luck with how the stopbands interact when two SAW filters are connected in series like this. Probably best to wait until RFDUK gets the third analyser to try out.

The zigzag nature of the spurious as described by TurboTom in post #13 and by rf-loop is exactly what I'd expect to see because the analyser is in FFT mode for all the screenshots I have seen so far.

[rf-loop]

I think the frequency hopping is due to the fact that the analyzer does the analysis based on an FFT. If FFT is involved the LO probably is set at fixed intervals.
You can try and deselect FFT, and see if the frequency hopping still occurs...

I did not wonder at all this hopping. Naturally and of course I know it. But I tried demonstrate this to some other peoples who are not familiar with this equipment but interested how example this spur act. Also tiny bit more information for purpose if some people want think what are possible sources for this mixing product (spur). (here is also peoples who do not have this equipment but still want think this case with very deep knowledge about this kind of equipments )

[rf-loop]

I really don't think anyone should take their analyser apart yet but if anyone is brave enough to take their analyser apart then please be VERY careful not to flex the big PCB because you could easily cause cracks inside the many ceramic SMD caps on the main board. Even a tiny amount of flex/stress could damage lots of capacitors. Not good!

We don't know what is causing the variability in rejection. It could be they changed something on the PCB or it could be a metalwork/isolation issue. It could just be bad luck with how the stopbands interact when two SAW filters are connected in series like this. Probably best to wait until RFDUK gets the third analyser to try out.

The zigzag nature of the spurious as described by TurboTom in post #13 and by rf-loop is exactly what I'd expect to see because the analyser is in FFT mode for all the screenshots I have seen so far.

Yes, this warning is extremely important. We who are familiar with this kind of things know how to handle these, even more fragile things,  but... there is lot of peoples who do not know....

Idea for this tiny test was just because previously I understand you think this (after TurboTom msg) and I want support your thinking  so that now you know, without this equipment in your hand, that it is as you think.

[Performa01]

I think the frequency hopping is due to the fact that the analyzer does the analysis based on an FFT. If FFT is involved the LO probably is set at fixed intervals.

I think this is why rf-loop added the text “Because this is frequency hopping sweep spectrum analyzer…” to his 2nd image


-----------------------------------------------------------------------
Btw. I have asked my friend for some more tests and it’s now confirmed that the spur is related to the input signal in a linear way. He has tested this for mixer levels of -40dBm - -20dBm.

So it actually would be some sort of image response and I think the concerns voiced by rf-loop, regarding poor contact (or no contact at all) between aluminum and the PCB traces sound very plausible to me. Trying to contact aluminum usually is a true nightmare…

[RFDUK]

I think the frequency hopping is due to the fact that the analyzer does the analysis based on an FFT. If FFT is involved the LO probably is set at fixed intervals.

I think this is why rf-loop added the text “Because this is frequency hopping sweep spectrum analyzer…” to his 2nd image



-----------------------------------------------------------------------
Btw. I have asked my friend for some more tests and it’s now confirmed that the spur is related to the input signal in a linear way. He has tested this for mixer levels of -40dBm - -20dBm.

So it actually would be some sort of image response and I think the concerns voiced by rf-loop, regarding poor contact (or no contact at all) between aluminum and the PCB traces sound very plausible to me. Trying to contact aluminum usually is a true nightmare…

Yes, very much agree with both additional points ... Btw ...

The unit to unit range of performance on this spur is typically -70dBC for an older instrument, -57dBC on my first and then -50dBC on my second. Poor aluminium screen contact to the PCB is a strong favourite for this wide range.

[TurboTom]

I consider the cover issue only valid if Siglent changed from the machined parts to completely die-cast configuration without any post-processing. CNC machining is so accurate nowadays that even if they only machine the surface mating with the PCB, shielding performance should be good enough that there wouldn't be the inaccuracies present that we are observing on the recent instruments. If Siglent doesn't employ any post-processing of the cast components, okay. But since machining of the covers only requires any dated three-axis-mill, I don't think they will risk the problems induced by using bare, die-cast shields. Anyway, I may be proven wrong - which would be a relly stupid move on behalf of the manufacturer...  . I would be curious to see a recent SSA being torn down for ananlysis...though I wouldn't recommend anyone to do this.

Cheers,
Thomas

[RFDUK]

I consider the cover issue only valid if Siglent changed from the machined parts to completely die-cast configuration without any post-processing. CNC machining is so accurate nowadays that even if they only machine the surface mating with the PCB, shielding performance should be good enough that there wouldn't be the inaccuracies present that we are observing on the recent instruments. If Siglent doesn't employ any post-processing of the cast components, okay. But since machining of the covers only requires any dated three-axis-mill, I don't think they will risk the problems induced by using bare, die-cast shields. Anyway, I may be proven wrong - which would be a relly stupid move on behalf of the manufacturer...  . I would be curious to see a recent SSA being torn down for ananlysis...though I wouldn't recommend anyone to do this.

Cheers,
Thomas

That got me thinking on the aluminium contact areas to the PCB in the region of the 3rd mixer and input SAW filters. Here are a couple of picts from Dave's teardown.

Can anyone explain the patchy layer that only partially covers the screen cover contact areas on the SAW filter side of the PCB?

Another variabilty could be the solder resist integrity. PCB manufacturer 'keep out' settings sometimes deliver not as intended resist dimensions. Excessive resist dimensions could perhaps get under the aluminium contact area?

Are the groundplane void slots bridged by the aluminium screen wall? There is a witness line running into one of the slots from the cover.

[nctnico]

I strongly doubt changes in casting or milling will have a large effect on how the PCB (doesn't) make contact with the case. After all the aluminium will be covered with an insulating oxide skin anyway. A change in components is much more likely.

[RFDUK]

Interesting observation. The milled housings would benefit from an Alocrom coating or similar.

[G0HZU]

I would expect that the aluminium would be coated after machining but it should be a conductive coating not insulating. I seriously doubt they would use a coating that insulated the aluminium. At work we have been making RF PCBs like this for decades and have tried various types of screening. All our machined aluminium screens are coated and the coating is conductive. It's hard to tell they are coated with a casual glance.

How well the screens work (or don't work) depends a lot on the type of RF circuits they are covering so it isn't always obvious how much grief the screens can cause if something is lacking. There are also lots of things that can cause variation on screening performance when making basic screens like this. Often its possible to examine a dozen identical screens and spot flaws or differences with the naked eye. Sometimes the edge deburring gives variable results and other times there can be subtle issues with the milled faces. Other times, contaminants can get on the PCB or the metalwork and these can be hard to spot unless a magnifier is used. Other times there simply aren't enough screws or the PCB surface itself isn't as flat as hoped. Sometimes, RF absorber is needed to be stuck inside the lid of the milled pockets. For our high performance products we now use a squashy EMC 'filler' that sits in a groove in the machined faces. This works a lot better than trying to make a reliable and repeatable seal using just flat machined faces against a PCB.

Whatever the cause for the poor image rejection, I think it is affecting all of the analysers that I've seen in this thread to some degree because I doubt that the designer would have wanted 'only' -70dBc rejection here. We often use cascaded SAW IF filters at work but we generally put active or passive parts in between them (to help prevent passband and stopband issues) and try and have plenty of screws holding the metalwork together at vital locations like this. Even -70dBc image rejection here is not that good despite the low cost of this analyser.

[nctnico]

True but all those extra measures mean extra cost for a mass produced low cost spectrum analyser. If it where my design I'd try very hard to not make it depend on mechanical stuff being done exactly right. Also 15 dB difference between the specification and actual circuit seems like a lot to me for a problem with shielding. I think pictures of the inside of a newer model would shine a light on what may be causing the problem.

[G0HZU]

Yes, it could be they changed the SAW filters or maybe changed something about the PCB or the metalwork or maybe the design needs some RF absorber. Usually, if there is a metalwork issue then pressing or squeezing the lid (or tweaking with the screws) will change the level of the unwanted spurious signal a bit.

[TurboTom]

Yeah, maybe Siglent just fired the guy with the Popeye-like forearms who used to tighten the screws on the previous machines for eating too much spinach and replaced him with a tiny woman... 

Whatsoever, I've got to agree with nctnico that only a shielding problem without any additional change in hardware would not be very likely to have so much effect to change the image frequency rejection by 20dB on some machines. But I'm quite certain that here on the forum, we will find out the culprit for the problems sooner or later.

Cheers,
Thomas

[G0HZU]

Whatsoever, I've got to agree with nctnico that only a shielding problem without any additional change in hardware would not be very likely to have so much effect to change the image frequency rejection by 20dB on some machines.

Doesn't that depend on what makes up the final (image) signal you see at the input to the third mixer? I don't know what your background/experience is but usually a metalwork issue can cause summing/cancelling effects depending on the phase and amplitude of whatever signal paths can conduct or leak to the input of the third mixer. If two signal paths arrive here at the same amplitude (-60dBc?) but unknown phase, then you could get >30dB cancellation or you might get a 6dB summing effect depending on phase. So >36dB variation in such a case? Tweaking a screw slightly can make a big difference in this scenario if it spoils a cancellation effect for example..

I can't tell for certain of the metalwork is OK. Where I work we would have to look at the drawings and get our hands on the hardware and do some tests to be as certain as you. Even then, there could be problems with yield when tested across (say) 100 units. But you seem confident the metalwork is OK? It might help if you gave something about your background and experience wrt RF converter design and testing?

[rf-loop]

It looks like many peoples have more like audio experience than rf.

But then, just like G0HZU told there really can be many reasons including this aluminium block. Also I do not want release any part from list of suspects.

If we get true random problem distribution and we find older and new units randomly have some units what have clearly more bad this -60MHzc spurious then situation is different. Now we have only very small amount of data. How many observations we have! With this data we can not even tell sure that all older units are "good" and more new units "bad". Just this we can not do exept if we jump to world of  trumpths instead of truths.
Only we know that  some devices have been detected with quite high input related spurs, out of specifications. And these these very few observations have been with these more new manufactured units. But how many older units we have real test data. Only a few.

But also we have at this time no older unit what show this bad. This counter is still zero.
Also we do not know if there is good "new"  units. 

We can now suspect that perhaps there is something changed and perhaps more new units have this high spur. But at same time we do not know if there is also somewhere some thing better if Siglent have changed some things. Some times these kind of things  go sdo that make one thing better other think may slip more bad.
Also it looks like same time when this individual named spur is rised also these units have rised noise floor!!  Perhaps need also take it into thinking. 

But even with this small amount of observations I'm very interested to see what are internal all changes between older and newer units!

Of course when equipment is clearly out of specifications thisa must not acvcept. But inside specifications we need accept all variations. What ever variations.

We do not even know at this time what signals and where produce this spur. So we can not say if it is more or less like signals shielding problem between parts of circuit or some components characteristic problem if they have changed some component type or just manufacturer.
But still commonly can say that shielding is much more complex and difficult to predict than just digital-audio-LF peoples think mostly.
Many times it need lot of experimental work. Some times it still is like magic because it is so complex that it is more easy to think magic than math. The less you know the easier things seem to be.



Also some times it is good to reset and take ground under foots and also reset the scale of thought.
Lets look somehow comparable (mostly more bad) Keysight N9320B RF Spectrum Analyzer.
If we look input related spurious. (I can ask if I'm a little nasty, did Keysight designer want this high level of spurius and why)

Keysight N9320B Spurious response specification:
Input related spurious < -60 dBc | -30 dBm signal at input mixer.


About Siglent. We need more observations. We need explanation what is this. Is it some component (also Al block and PCB is component) change to bad direction and how this is solved back to ok (or better)  or if these single units have just been failed units. If they are just defect units then explanation how these bad units can jump over factory quality control to factory out gate. (I do not accept transport damage explanation with this kind of failure. Nearly sure this failure have been there before it exit factory)

[Orange]

It looks like many peoples have more like audio experience than rf.

So instead of starting to insult 'peoples' Have you as a Siglent dealer, asked Siglent for a reaction on this issue ?

[rf-loop]

It looks like many peoples have more like audio experience than rf.

So instead of starting to insult 'peoples' Have you as a Siglent dealer, asked Siglent for a reaction on this issue ?

I talk here technical things what are my hobby and profession and what are interesting for me independent of if I some times sell some equipment or not. I'm much more interested about technical things than any kind of business.  Not talking "sales"man.
Also this is good place to talk things what also are sure read by Siglent.  Siglent RF designer engineer can answer here if he/she like.

[TurboTom]

I openly admit that I'm more experienced with digital, lower frequency and high power stuff than with RF/microwave circuitry but I tend to have quite a good "gut feeling" and I'm curious and brave (stupid??  ) enough to tear down my SSA for science's sake.

So please have a look at the attached photos. First of all, I found the RF PCB in my SSA to be warped round about 1mm in the centre -- probably this has no detrimental effect when it's sandwiched between the shielding plates. The fingerprints on the PCB don't originate from me but must have been there when the instrument left siglent's production line -- I handled the PCB only by the edges.
By the way, the lands of the shields completely cover the "isolation slots" as shown.

I removed the PCB, apparently it's exactly the same configuration as in Dave's teardown. And now I put some standoffs in the places where the long screws bolt the RF assembly to the chassis in order to install the RF PCB completely witout any shielding.

So please have a look at the screenshots... (full span is without input signal, just for comparison and to visualize the effect of the missing shields). I guess this rules out the (suggested lack of) shielding as the cause for the 60MHz spur one for all times.

Cheers,
Thomas

[rf-loop]

I openly admit that I'm more experienced with digital, lower frequency and high power stuff than with RF/microwave circuitry but I tend to have quite a good "gut feeling" and I'm curious and brave (stupid??  ) enough to tear down my SSA for science's sake.

So please have a look at the attached photos. First of all, I found the RF PCB in my SSA to be warped round about 1mm in the centre -- probably this has no detrimental effect when it's sandwiched between the shielding plates. The fingerprints on the PCB don't originate from me but must have been there when the instrument left siglent's production line -- I handled the PCB only by the edges.
By the way, the lands of the shields completely cover the "isolation slots" as shown.

I removed the PCB, apparently it's exactly the same configuration as in Dave's teardown. And now I put some standoffs in the places where the long screws bolt the RF assembly to the chassis in order to install the RF PCB completely witout any shielding.

So please have a look at the screenshots... (full span is without input signal, just for comparison and to visualize the effect of the missing shields). I guess this rules out the (suggested lack of) shielding as the cause for the 60MHz spur one for all times.

Cheers,
Thomas

Lot of thanks about this. So, now need in the first instance think other reasons.

What they have changed  (or is it still possible these bad examples have been somehow defected units  -- what feels very unlikely because RFDUC get one bad unit after one bad)




It was also my plan to soon tear down my SSA and do around same things after 1-3 days when I have first cleaned my work bench which had just been prepared allready for some SDS1202X-E repair-reworks.




EDIT/ADD:

As previously suspected. Main reason IS shielding/Aluminium block.
Some metal work supplier have done some tiny material surface changes in aluminium shielding block. This may cause this problem in some individual units.
Siglent will repair all units delivered back to Siglent what suffer  this issue.

It is (IMHO) also possible that there is quite simple solution for DIY repair if user have enough knowledge and skills for handling this kind of very sensitive and fragile things inside this kind of equipment,  but in mainstream: Siglent have done this manufacturing error, Siglent is responsible.

[G0HZU]

So please have a look at the screenshots... (full span is without input signal, just for comparison and to visualize the effect of the missing shields). I guess this rules out the (suggested lack of) shielding as the cause for the 60MHz spur one for all times.

Thanks for doing this. Forgive me for appearing a bit stubborn here but your published tests are interesting but not conclusive (yet)... 

By taking off the lid completely you remove one potential leakage path (via the metalwork) and replace it with an open air radiated path. So its difficult (for me at least) to draw any definite conclusions yet.

Based on this single test, what would you have concluded if the spur appeared lower or higher than before?  I'm not sure I could conclude very much in either case. I'm still being cautious here because I've been down this route many times in the past with screens.

You may have already tried this but a better test would be to fit the lid with the screws only partly tight and then wiggle and press it to see if the spur moves as the lid is pressed and the screws tightened. If it doesn't budge then I guess the metalwork can be ruled out with a fair degree of confidence. But obviously you have to be careful here if the metalwork doesn't have a locating dowel. You could easily short out and damage components if you try this.

[TurboTom]

I already thought about doing this as well and I will upon reassembly (don't kow if this will happen today though...). Yet, since the level ratio of the 60MHz spur virtually didn't change at all with the shields removed, it would surprise me a lot if an improperly tightened shield would make all the difference. Even now, there should be some signal reflected back into the circuitry by the metal chassis of the instrument which is located approx. 15mm parallel to the PCB. And for the other spurs, the effect of the shields is more than evident.

Now that it's apart, does anybody want me to take some more measurements? Maybe a more accurate measurement of the observable spurs? Unfortunately, I haven't got any instrument available that would permit me to check for the frequencies of the LOs, at least not for the very high frequency ones.

Cheers,
Thomas

[G0HZU]

Now that it's apart, does anybody want me to take some more measurements?

Yes, but RFDUK may be better placed to do the tests below as he has an xGHz analyser and should be able to repeat the earlier LO leakage tests but this time at CFs of 780 and 3120MHz.

One thing about our current frequency plan estimate is that it puts LO2 (3.120GHz) inside the range of the 3.2GHz analyser. Also, LO3 at 780MHz is inside the range of the analyser. So it would be interesting to see what happens to the frequency plan once the analyser gets tuned at or near to these frequencies. One option would be to shift IF1 up to about 4.17GHz. There may be enough bandwidth in the IF1 filter to allow this. Or maybe they sidestep IF2 slightly.

[Performa01]

Thank you very much, Thomas, for digging so deep into that issue (even though your instrument isn't even affected.
My hat goes off to you! 

I agree with G0HZU, in some circumstances poor shielding can make matters far worse than no shielding at all.

On the other hand, as tempting as the thought about a shielding issue has been, by now I'm inclined to believe it's not the culprit after all. It would still be nice if you can do some more tests with that aluminum block - now that you have torn appart your instrument already...

Thanks again!

[Joel_l]

This got me curious so I looked at mine.

Signal generator - WaveTek 2410, cable - 1M LMR400

SA - HW 07.03.00, Manufactured 02-2017

I also don' get -70dB

I also notice my floor seems a little higher than others.

[G0HZU]

On the other hand, as tempting as the thought about a shielding issue has been, by now I'm inclined to believe it's not the culprit after all. It would still be nice if you can do some more tests with that aluminum block - now that you have torn appart your instrument already...

Yes, I'm almost convinced we can rule out the metalwork.

With the PCB being slightly bowed, obviously take care how you tighten the screws as you don't want to store stress in the centre of the PCB via the pattern you choose to tighten the screws.

[RFDUK]

Now that it's apart, does anybody want me to take some more measurements?

Yes, but RFDUK may be better placed to do the tests below as he has an xGHz analyser and should be able to repeat the earlier LO leakage tests but this time at CFs of 780 and 3120MHz.

One thing about our current frequency plan estimate is that it puts LO2 (3.120GHz) inside the range of the 3.2GHz analyser. Also, LO3 at 780MHz is inside the range of the analyser. So it would be interesting to see what happens to the frequency plan once the analyser gets tuned at or near to these frequencies. One option would be to shift IF1 up to about 4.17GHz. There may be enough bandwidth in the IF1 filter to allow this. Or maybe they sidestep IF2 slightly.

Second instrument returned last week so no SSA3032X here now.

[RFDUK]

Does anyone know what component 'U27' is after the pi pad at the SAW filter input?

Is that just a test node?

[G0HZU]

It would make sense to have a roofing LPF somewhere between the second and third mixers and U27 could therefore be a small SMD LPF. It could also be a thermopad but my guess would be that it's a LPF that helps improve the isolation between mixer 2 and 3 up in the xGHz region.
However, I just spotted that the other SMD LPFs near the first mixer are labelled Z1 and Z2. So maybe this part would be labelled Z3 if it was a SMD LPF? Maybe it's a tiny BPF rather than a simple LPF. But then again it could be something completely different.

[RFDUK]

The photo here is the highest resolution take on that area I could find.

I'm finding Johanson LPF products that fit the size, appearance and 6 connection pin out.

[tautech]

It looks like many peoples have more like audio experience than rf.

So instead of starting to insult 'peoples' Have you as a Siglent dealer, asked Siglent for a reaction on this issue ?

I talk here technical things what are my hobby and profession and what are interesting for me independent of if I some times sell some equipment or not. I'm much more interested about technical things than any kind of business.  Not talking "sales"man.
Also this is good place to talk things what also are sure read by Siglent.  Siglent RF designer engineer can answer here if he/she like.

All readers can be very sure Siglent are informed of this matter and are working on and watching developments.
They have indicated that they will inform us of their findings.....in what detail and when, only time will tell.

It is my view to leave them to fully investigate why spurs do not meet spec and not press them for fast and short answers.

[RFDUK]

It looks like many peoples have more like audio experience than rf.

So instead of starting to insult 'peoples' Have you as a Siglent dealer, asked Siglent for a reaction on this issue ?

I talk here technical things what are my hobby and profession and what are interesting for me independent of if I some times sell some equipment or not. I'm much more interested about technical things than any kind of business.  Not talking "sales"man.
Also this is good place to talk things what also are sure read by Siglent.  Siglent RF designer engineer can answer here if he/she like.

All readers can be very sure Siglent are informed of this matter and are working on and watching developments.
They have indicated that they will inform us of their findings.....in what detail and when, only time will tell.

It is my view to leave them to fully investigate why spurs do not meet spec and not press them for fast and short answers.

I don't mean to be confrontational I really don't, but your representations are patronising in the extreme and I'm sure unhelpful to the Siglent brand. This is the second input you've made and the first was similarly unhelpful, although I resisted making a point of it.

I ordered the instrument almost 3 months ago. I've had two instruments delivered that fall well short of warranted specification. I've had zero feedback from Siglent or my supplier. I'm still on board with Batronix in the hope the problem will be explained to me, the remedial timescale outlined and an instrument delivered in a reasonable (to me) timeframe.

After nearly 3 months I'm not looking just for 'fast answers', I just want the instrument I paid for, cash drawn down on the day of order.

Coming from a Siglent representative, your views reflect a lack of commercial sensitivity to put it lightly.

I've patiently stuck with it because I believe the SSA3032X to perform well and offer good value.

[tautech]

It looks like many peoples have more like audio experience than rf.

So instead of starting to insult 'peoples' Have you as a Siglent dealer, asked Siglent for a reaction on this issue ?

I talk here technical things what are my hobby and profession and what are interesting for me independent of if I some times sell some equipment or not. I'm much more interested about technical things than any kind of business.  Not talking "sales"man.
Also this is good place to talk things what also are sure read by Siglent.  Siglent RF designer engineer can answer here if he/she like.

All readers can be very sure Siglent are informed of this matter and are working on and watching developments.
They have indicated that they will inform us of their findings.....in what detail and when, only time will tell.

It is my view to leave them to fully investigate why spurs do not meet spec and not press them for fast and short answers.

I don't mean to be confrontational I really don't, but your representations are patronising in the extreme and I'm sure unhelpful to the Siglent brand. This is the second input you've made and the first was similarly unhelpful, although I resisted making a point of it.

I ordered the instrument almost 3 months ago. I've had two instruments delivered that fall well short of warranted specification. I've had zero feedback from Siglent or my supplier. I'm still on board with Batronix in the hope the problem will be explained to me, the remedial timescale outlined and an instrument delivered in a reasonable (to me) timeframe.

After nearly 3 months I'm not looking just for 'fast answers', I just want the instrument I paid for, cash drawn down on the day of order.

Coming from a Siglent representative, your views reflect a lack of commercial sensitivity to put it lightly.

I've patiently stuck with it because I believe the SSA3032X to perform well and offer good value.

On 31 Dec (NZ time) when your 2nd SSA was shown to also not be within spec it was obvious there appeared to be a problem.
Until then it was appropriate that your local dealer deal with this issue and us just watch developments.

Since then, this has been risen up to be placed on Siglent's doorstep since which there has been two weekends lost also.
Unlike some of us enthusiasts, paid staff only work so many hours/week to deliver the answers you and us seek.

So for fear of you taking this the wrong way, this issue to Siglent (as far as we know) is only a few days old.
Please consider this ^.
They need time to explore the cause and report back via rf-loop and/or other Siglent dealers like myself whom are also present on EEVblog.

I'm sorry and understand that 3 months for you is frustrating and I hope we can have answers before this drags out much longer for you.

[RFDUK]

It looks like many peoples have more like audio experience than rf.

So instead of starting to insult 'peoples' Have you as a Siglent dealer, asked Siglent for a reaction on this issue ?

I talk here technical things what are my hobby and profession and what are interesting for me independent of if I some times sell some equipment or not. I'm much more interested about technical things than any kind of business.  Not talking "sales"man.
Also this is good place to talk things what also are sure read by Siglent.  Siglent RF designer engineer can answer here if he/she like.

All readers can be very sure Siglent are informed of this matter and are working on and watching developments.
They have indicated that they will inform us of their findings.....in what detail and when, only time will tell.

It is my view to leave them to fully investigate why spurs do not meet spec and not press them for fast and short answers.

I don't mean to be confrontational I really don't, but your representations are patronising in the extreme and I'm sure unhelpful to the Siglent brand. This is the second input you've made and the first was similarly unhelpful, although I resisted making a point of it.

I ordered the instrument almost 3 months ago. I've had two instruments delivered that fall well short of warranted specification. I've had zero feedback from Siglent or my supplier. I'm still on board with Batronix in the hope the problem will be explained to me, the remedial timescale outlined and an instrument delivered in a reasonable (to me) timeframe.

After nearly 3 months I'm not looking just for 'fast answers', I just want the instrument I paid for, cash drawn down on the day of order.

Coming from a Siglent representative, your views reflect a lack of commercial sensitivity to put it lightly.

I've patiently stuck with it because I believe the SSA3032X to perform well and offer good value.

On 31 Dec (NZ time) when your 2nd SSA was shown to also not be within spec it was obvious there appeared to be a problem.
Until then it was appropriate that your local dealer deal with this issue and us just watch developments.

Since then, this has been risen up to be placed on Siglent's doorstep since which there has been two weekends lost also.
Unlike some of us enthusiasts, paid staff only work so many hours/week to deliver the answers you and us seek.

So for fear of you taking this the wrong way, this issue to Siglent (as far as we know) is only a few days old.
Please consider this ^.
They need time to explore the cause and report back via rf-loop and/or other Siglent dealers like myself whom are also present on EEVblog.

I'm sorry and understand that 3 months for you is frustrating and I hope we can have answers before this drags out much longer for you.

I have a suggestion to help Siglent ...... Siglent 'distributors' do one of two things ...
a) don't identify themselves as such on forums if they wish to constructively contribute to 'in-house' issues similar to this, or
b) refrain totally from involvement with 'in-house' related threads of this nature.

Nothing personal, but your input in this thread has raised more questions for me about just what I've invested my cash in than otherwise would have been the case.

[TurboTom]

My SSA has undergone some more testing and I have to admit that -- at least partially -- I was wrong with my assumptions, so here we go:

First, before attempting anyting else, I took several screenshots in 50MHz span intervals and 10kHz resolution bandwidth in completely unshielded configuration. Input of the SSA was left open. Since probably not too many readers may be interested in this bunch of screenshots, I packed them all up in a single ZIP file.

After that, reassembly of my SSA commenced. Initially, I only sandwiched the RF board between the shields and put in the long screws, labeled "1" but didn't tighten them at all.  The whole assembly was rattling like a can filled half-way with dry beans...

The full span spectrum shows a whole forest of spurs, apparently even stronger than without any shields at all. The 60MHz spur is also much stronger than it was initially and also stronger than without the shields, averaging in at approx. 64dBc. Yet, this figure alone is almost within spec (65dBc) but far off compared to a good instrument (>70dBc). But with only about 25% of the screws and none of them tightened at all, that's probably no surprise. There was approx. 1mm play in the screws until they were seated.

Next step was tightening the long screws but still leaving out the short ones. In that configuration, I unfortunately made a mistake with the SSA settings -- sorry gals and guys -- I left the attenuator at -20dB so it doesn't tell that much about the SSA's performance. The 60MHz spur at least doesn't emerge from the noise floor. Apparently, the SSA performs within specs in this configuration.

In the final run, I had some cans of spinach  (...Popeye...) and inserted and tightened all the screws and took one more screen shot of the 60MHz spur. I guess 72dBc is as good as it will get on my machine...

So my conclusion is -- yes, the shields may have some effect but unless they are machined completely inaccurately or not properly seated at all, they shouldn't push the SSA's performance out of spec. So there has to be something else wrong with the (more recently manufactured) machines that don't meet the specs.

By the way, the shields of my SSA are pretty accurately made and each has got two alignment pins that fit into bores of the RF PCB so the assembly position of the shields is accurate to within approx. one tenth of a millimetre. Not shabby at all I'ld say...

I hope I could shed some light on the shielding situation of the Siglent SSA and its influence of the instrument's performance.

Cheers,
Thomas

[G0HZU]

Thanks again for doing these tests. It does look fairly benign even with loose screws. It doesn't leave much else to play with unless they changed something to do with the SAW filters themselves. Maybe a different supplier or a batch issue. Or maybe something changed in the PCB/mechanical layout in the later units.

I don't have any experience of directly cascading two SAW filters without also having some degree of resistive loss or active isolation between them so I can't say what the risks (to stopband performance) are if the filters are connected directly like this. I suppose in theory it might be possible to get a spiky stopband resonance if there was a conjugate match (with a low resistive loss) at the image frequency. But that would be a bit unlucky. Maybe adding a small amount of ESR in the form of a tiny series SMD resistor (of just a few ohms?) between the two filters would damp a stopband resonance. But I'm just guessing again. I've never tried this with SAW filters.

[G0HZU]

In case anyone hasn't seen the SAW filter datasheet, here's a typical response plot for a single NDF8027. I assume this is the correct datasheet and it shows over 50dB rejection at 750MHz with a single SAW filter. At work, we generally use two SAW filters but with something in between them and it's usually possible to get very good overall stopband performance. Something has to be very wrong if some units are only getting 51dB rejection if we assume they are still trying to use a pair of similar SAW filters in the Siglent analyser.

[Orange]

Perhaps Siglent used a different SAW filter, which has lesser specs. It would also explain the raised noise level that has been observed with these new analysers.

If the new type SAW filter has more pass-band attenuation, the dynamic range of the whole RF chain will suffer. Simply replacing the SAW filter will give you an un-calibrated instrument......
Again this is pure speculation.

Looking forward to see a reaction from Siglent to see what the real reason is of this deficiency in the analyser.

[RFDUK]

I've had no information back from Siglent or my distributor. So still no acknowledgement there is an issue and no timeframe outlined for a replacement.

It remains interesting to know if any other owners of 2017 manufactured SSA3000 series instruments could post -dBC performance numbers on the input related spurious that appears approximately 60MHz below the wanted input signal. Please refer to the plots at the start of this thread for examples of instrument setup.

[rfspezi]

I just did the test with my brand new ssa.
Got a delta of 55,4 dB. 
By the way... did your units come with a screen protector foil or not?

[RFDUK]

I just did the test with my brand new ssa.
Got a delta of 55,4 dB. 
By the way... did your units come with a screen protector foil or not?

Thanks for posting and very sorry to hear that.

I've had two (faulty) instruments in the last several weeks, neither had a screen protector.
I figured that's normal now, I noticed in a teardown video of an older instrument the screen protector was fitted new and wondered about that too.

[tautech]

By the way... did your units come with a screen protector foil or not?

It's quite unusual if units come with screen protection now.
The vast bulk of the Siglent range are no longer shipped with them.
The only exception was a SDG2042X (AWG) that I got in December and that range also being touch screen might be some reason why protection is still included. These still are quite usable with the overlay.
Maybe it was just older factory stock. 

I have occasionally had problems with older demo units and the overlay has not peeled cleanly leaving behind a gel like substance but this can be easily rubbed off with a cloth.
This toughened non-reflective glass is pretty tough stuff and arguably doesn't need an overlay for protection.

[rfspezi]

I've had two (faulty) instruments in the last several weeks, neither had a screen protector.

Do you have a correctly working unit in the meantime?

By the way, i am just playing around with the spurious.
Feeding in a 100 MHz AM-modulated (50%, 1MHz) signal gives me peaks at 40 MHz (=carrier), 49 and 51 MHz (=sidebands).
Feeding in a 110 MHz AM-modulated (50%, 1MHz) signal gives me peaks at 50 MHz (=carrier), 39 and 41 MHz (=sidebands).

The difference between the real sideband signals and the spurious are only 40 dB. 
Hmm... not sure what to think now...

[EDIT]
Find attached the screenshot of the 100 MHz signal mentioned above.

[RFDUK]

I've had two (faulty) instruments in the last several weeks, neither had a screen protector.

Do you have a correctly working unit in the meantime?

No I don't have an instrument here, I'm in dialogue with Batronix.

[RFDUK]

Thanks for the plot rfspezi, applying AM mod was an interesting thing to do as it turns out.

This is looking like the performance of a very poorly analyser.

[rfspezi]

This is looking like the performance of a very poorly analyser.

Just my thoughts...
I would love to see a fix for that since otherwise i really like that spectrum analyzer.

[rfspezi]

Here are some more interesting spurious from a 70 and 80 MHz AM-modulated (50%, 1MHz) signal.
Seems there is something happening around 75 MHz. 

[RFDUK]

What is the signal source?

[rfspezi]

What is the signal source?

It's a SDG2122X.
Can't exclude that the sideband effects come from it.
Would be great if somebody else could verify the measurement with a different source?

Varying the carrier of the modulated AM-source shows that the sidebands (and only them) get mirrored at 75 MHz.
The carrier spurious always occurs 60 MHz below the true carrier frequency.

[PA2HK]

Yes, interesting topic. I also have a new Siglent SSA3021X, manufactured in 2017, that I have recently bought about 4 weeks ago. Must say, very nice unit offered at a good price. Indeed.

I have ran three tests at 144Mhz, 433Mhz and 1285Mhz analog to what we have seen before in this thread.

SSA system information:
SW1: 1.2.8.3
SW2: 20170512-1
SW3: 00000001
HW: 07.03.00
Calibration: 2017-09-19

Signal source is Agilent E4421B generator connected to the Siglent SA via 2 meter Coleman RG213 interconnect. Needless to say, my unit also shows spurs and unfortunately does not seem to match the specification of minimal -65dBc.

145MHz, spur -60MHz with -61dBc


433MHz, spur -61MHz with -61dBc


1285Mhz, spur -60MHz with -60dBc

[RFDUK]

I requested a refund and that has been agreed by Batronix ASAP to allow me to make other arrangements. I'll post confirmation that loop works effectively as soon as funds are returned.

It's been an interesting ride and I'm wiser for it with regards to buying new 'economy' test instruments .... but also a little stressed and late on some projects

I'll be interested to read how this pans out technically speaking for other folks, good luck 

[cncjerry]

There must be something else going on with reference to the modulation.  I can't believe the analyzer is smart enough to demod the signal and spit the sidebands out all over the place.  It looks more like IMD, no?

If you move the 60Mhz spur into the center and zoom in on it with a narrow(er) span, lower the RBW, you should see the AM mod on the original spur assuming it isn't in the noise, I would think. 

[Orange]

I requested a refund and that has been agreed by Batronix ASAP to allow me to make other arrangements. I'll post confirmation that loop works effectively as soon as funds are returned.

It's been an interesting ride and I'm wiser for it with regards to buying new 'economy' test instruments .... but also a little stressed and late on some projects

I'll be interested to read how this pans out technically speaking for other folks, good luck 

Sorry to hear that this is the 'solution' for you. I'm somehow disappointed in Siglent and Batronix to let this happen. The analyser has great potential, and the first models did fine on this aspect. My own analyser does roughly 65 dBc. It is meeting the published specs (just), but I can live with it. Let's face it, where do you find a new analyser that does 3.2 GHz, with TG for 1700 euros....
My other analyser, a Rigol 815TG, does not come near the Siglent in terms of IMD and freq. range and sensitivity.

Please let us know what you next analyser will be.....

[DonRon]

Hi!

I bought my SSA3021 in December 2017.
Made the test in the range betwenn 100 and 200 MHz and observed the same results as PA2HK - Delta is around - 61 dBm.
Also measured the noise level, it's -97 dBm at 100 MHz.
My unit is HW 07.03.00 and calibration date is 2017-09-18

Cheers,

Ronald

[rfspezi]

Let's face it, where do you find a new analyser that does 3.2 GHz, with TG for 1700 euros....

...not 1.700 but 2.700€ for the 3.2GHz version.

I did another measurement using a 50% 1MHz AM-modulated 100MHz sine (SDG2122X).
The around 75MHz mirrored sidebands are most likely coming from the function generator.
But what i don't understand are the non 1MHz but 1.5MHz spaced sidebands around the 40MHz spurious?

[Emo]

OK,

Also took the measurements

SW1 1.2.8.5a
SW2 20170512-1
SW3 000000D1
HW 07.03.00
Calibration 2016-12-19

RF gen Philips PM5390A
Note; This generator delivers some spurs on 80Mhz-90Mhz below and above depending output frequency

Edit Compared to PA2HK, the HW is the same, SW 1 differs, but calibration date is later. Could someone at Siglent have made some different routine for calibration??

[Orange]

Let's face it, where do you find a new analyser that does 3.2 GHz, with TG for 1700 euros....

...not 1.700 but 2.700€ for the 3.2GHz version.

I did another measurement using a 50% 1MHz AM-modulated 100MHz sine (SDG2122X).
The around 75MHz mirrored sidebands are most likely coming from the function generator.
But what i don't understand are the non 1MHz but 1.5MHz spaced sidebands around the 40MHz spurious?

You need to extend it's possibilities in a clever way, and turn a 2.1GHz into 3.2GHz, and for sure you get it for 1700, but don't tell Siglent :-)

[TurboTom]

Let's face it, where do you find a new analyser that does 3.2 GHz, with TG for 1700 euros....

...not 1.700 but 2.700€ for the 3.2GHz version.

I did another measurement using a 50% 1MHz AM-modulated 100MHz sine (SDG2122X).
The around 75MHz mirrored sidebands are most likely coming from the function generator.
But what i don't understand are the non 1MHz but 1.5MHz spaced sidebands around the 40MHz spurious?

That's one of the results of the way the SSA works. The 3rd IF is not demodulated (rectified) as in an analog SA but it's digitized and analyzed via FFT. This takes place in segments of approx 1.25MHz (as we understand it currently). In these "bins", the "60MHz Spur" appears to be mirrored, i.e. an increasing carrier frequency lets the mirror spur decrease in frequency (as long as it stays within the bin). Have a look at rf-loop's post where he very nicely explains and illustrates this peculiarity: https://www.eevblog.com/forum/testgear/siglent-ssa3032x-input-related-spurious-99091/msg1391448/#msg1391448

At a modulation frequency of 1MHz, the side bands (and the carrier as well of course) spread over at least two adjacent bins, maybe even three, depending on the location of the carrier within "its" bin. Assuming the carrier is right at the centre of its bin (625kHz from either edge), the lower sideband's spur will be reflected to 375kHz apart from the lower bin's lower edge (which equals 875kHz span to the lower bin's upper edge) and the upper sideband's spur will be just mirrored, i.e. it will be located 875kHz apart from the upper bin's lower edge.

Now you've just got to add up the increments which is 875kHz + 625kHz = 1.5MHz, just like you reported. Depending on the location of the carrier, the arrangement of the spurs may even become asymmetric -- must be very confusing to watch if the operational principle of the SSA is unknown to the user.

Siglent should really have published some in-depth information on this instrument, pointing out its operation principles, block diagrams and some general figures like frequencies of the local oscillators and IFs to make understanding and interpreting such spurious signal easier for the user. Gone are the times of really detailed, comprehensive documentation of HP / Agilent equipment of the 1980s to early 2000s (probably also before that interval, but I haven't got much experience with such dated equipment). Then again, Siglent isn't what HP once was... 

[rfspezi]

Would be really interesting to do the test again with FFT turned off.

[RFDUK]

A couple of weeks ago I was waiting on a refund, but I had a change of heart when Batronix passed on confident reports from the factory regarding isolation of the problem.

Just received a new SSA3032X Manufactured Jan 2018 and all is well. The spur is looking very much like the earlier instruments at -71dBC, it's fixed.

Noise floor compared to the earlier instruments posted in the thread remains 3 to 4dB inferior. Checked against Siglent data sheet and this machine easily meets minimum spec and meets typical floor all the way up to 3.2 GHz, so no problem with that, very happy.

Winner winner .... you know the rest. Thanks to all who added useful information and technical interest to this thread.

[Orange]

A couple of weeks ago I was waiting on a refund, but I had a change of heart when Batronix passed on confident reports from the factory regarding isolation of the problem.

Just received a new SSA3032X Manufactured Jan 2018 and all is well. The spur is looking very much like the earlier instruments at -71dBC, it's fixed.

Noise floor compared to the earlier instruments posted in the thread remains 3 to 4dB inferior. Checked against Siglent data sheet and this machine easily meets minimum spec and meets typical floor all the way up to 3.2 GHz, so no problem with that, very happy.

Winner winner .... you know the rest. Thanks to all who added useful information and technical interest to this thread.

So the question we all have is 'What is causing this'

[rf-loop]

A couple of weeks ago I was waiting on a refund, but I had a change of heart when Batronix passed on confident reports from the factory regarding isolation of the problem.

Just received a new SSA3032X Manufactured Jan 2018 and all is well. The spur is looking very much like the earlier instruments at -71dBC, it's fixed.

Noise floor compared to the earlier instruments posted in the thread remains 3 to 4dB inferior. Checked against Siglent data sheet and this machine easily meets minimum spec and meets typical floor all the way up to 3.2 GHz, so no problem with that, very happy.

Winner winner .... you know the rest. Thanks to all who added useful information and technical interest to this thread.

Good!

The main reason was the previous major suspect as I write yesterday here (yesterday edit) :

https://www.eevblog.com/forum/testgear/siglent-ssa3032x-input-related-spurious-99091/msg1393911/#msg1393911

So, the "guilty" has been found and terminated. Everyone can breathe and sleep again and relax.

[Orange]

A couple of weeks ago I was waiting on a refund, but I had a change of heart when Batronix passed on confident reports from the factory regarding isolation of the problem.

Just received a new SSA3032X Manufactured Jan 2018 and all is well. The spur is looking very much like the earlier instruments at -71dBC, it's fixed.

Noise floor compared to the earlier instruments posted in the thread remains 3 to 4dB inferior. Checked against Siglent data sheet and this machine easily meets minimum spec and meets typical floor all the way up to 3.2 GHz, so no problem with that, very happy.

Winner winner .... you know the rest. Thanks to all who added useful information and technical interest to this thread.

Good!

The main reason was the previous major suspect as I write yesterday here (yesterday edit) :

https://www.eevblog.com/forum/testgear/siglent-ssa3032x-input-related-spurious-99091/msg1393911/#msg1393911

So, the "guilty" has been found and terminated. Everyone can breathe and sleep again and relax.

Relax ?.....
So anyone with this issue needs to contact Siglent right ?

[rf-loop]

A couple of weeks ago I was waiting on a refund, but I had a change of heart when Batronix passed on confident reports from the factory regarding isolation of the problem.

Just received a new SSA3032X Manufactured Jan 2018 and all is well. The spur is looking very much like the earlier instruments at -71dBC, it's fixed.

Noise floor compared to the earlier instruments posted in the thread remains 3 to 4dB inferior. Checked against Siglent data sheet and this machine easily meets minimum spec and meets typical floor all the way up to 3.2 GHz, so no problem with that, very happy.

Winner winner .... you know the rest. Thanks to all who added useful information and technical interest to this thread.

Good!

The main reason was the previous major suspect as I write yesterday here (yesterday edit) :

https://www.eevblog.com/forum/testgear/siglent-ssa3032x-input-related-spurious-99091/msg1393911/#msg1393911

So, the "guilty" has been found and terminated. Everyone can breathe and sleep again and relax.

Relax ?.....
So anyone with this issue needs to contact Siglent right ?

I meant that the cause of the problem was discovered. It would be a pretty stressful situation if the cause of the problem was not yet found. This, and only this, was the cause of my commentary. And it may not be unclear to anyone that I'm more interested in technology than trading, even if I sometimes do it.

I have also previously said that Siglent made this mistake and Siglent is responsible for it.
I think it is quite unequivocally said.
If I had sold a spectrum analyzer that is part of a potential problem set, I would contact the buyer or buyers and make a request for service. This is no more special than the fact that new cars are called to be repaired several times for many different reasons and constantly.
I do not take a stand on how someone else works. I will only take a position on what and how I do.

Just do not buy from sellers who do not have real after sales customer care.
Who ever suffer this isssue, imho, first place to contact is seller, not Siglent. Seller need handle this and seller seller cooperate with Siglent as/if nessessary and how need in different situations. This is main road - or least sales network need develop (and limit) so that it go to this way sooner or later. Better if yesterday..
If I have problem with my Sony TV I do not call Sony factory in Japan and I do not ask in some forum do I need really call Sony.  In the old days there was no ambiguity about where to go if the purchased item was not ok.

[rfspezi]

I am a bit concerned about how Siglent will correct the faulty units.
I assume they repair the units at their local service centers - so... will they be recalibrated after the modification or simply retuned to the sellers afterwards?

[Performa01]

I am a bit concerned about how Siglent will correct the faulty units.
I assume they repair the units at their local service centers - so... will they be recalibrated after the modification or simply retuned to the sellers afterwards?

Distributors are advised to send the analyzers back to the factory for repair (= replace the aluminum shielding block).

[PP7BB]

Is it possible to reveal marking of first new unit manufactured without this bug?
Some distributors might offer units not modified by Siglent. I hope Siglent will mark old units with new number. Without it we will not know if unit is free of this bug (newly manufactured or fixed by Siglent) or sit in wharehouse as it was produced with bug.

[rfspezi]

I am a bit concerned about how Siglent will correct the faulty units.
I assume they repair the units at their local service centers - so... will they be recalibrated after the modification or simply retuned to the sellers afterwards?

Distributors are advised to send the analyzers back to the factory for repair (= replace the aluminum shielding block).

How do you know?
Got any source?
To me it's more likely they send the replacement parts to their local service/repair centers and let them have the ssa's repaired.
That's why i fear there will be no calibration after repair.

[GDK_ATL]

Has anyone had any luck getting this fixed by either the dealer or SIGLENT? I bought mine from Saelig in October of 2017. I queried Saelig about the problem and they replied that:

Siglent is aware of the problem that you mentioned and are putting together a solution with the factory on this. The problem is not on all of the SSA3000X spectrum analyzers so part of the process is putting together a test to verify the unit has a problem and then getting everything in place to take care of the units that have problems. As soon as the details come in Siglent I will let everyone know how they will proceed going forward.

From reading about the issue here, I was under the impression that the problem had been identified by Siglent. Is that not the case?

[tautech]

Has anyone had any luck getting this fixed by either the dealer or SIGLENT? I bought mine from Saelig in October of 2017. I queried Saelig about the problem and they replied that:

Siglent is aware of the problem that you mentioned and are putting together a solution with the factory on this. The problem is not on all of the SSA3000X spectrum analyzers so part of the process is putting together a test to verify the unit has a problem and then getting everything in place to take care of the units that have problems. As soon as the details come in Siglent I will let everyone know how they will proceed going forward.

From reading about the issue here, I was under the impression that the problem had been identified by Siglent. Is that not the case?

This is the official position:
https://www.eevblog.com/forum/testgear/siglent-ssa3032x-input-related-spurious-99091/msg1393911/#msg1393911

I have one unit in stock affected and Siglent are sending me new shielding for installation.
Some dealers won't have the means to install them, therefore it's best left to an authorized service center.
Contact Saelig again or Siglent America in Ohio.

North American Headquarters
SIGLENT Technologies America, Inc
6557 Cochran Rd Solon, Ohio 44139
Tel: 440-398-5800
Toll Free:877-515-5551
Fax: 440-399-1211
info@siglent.com
www.siglentamerica.com

Edit
Siglent will ask for the SN#.

[TheSteve]

What about a re-calibration? There is no way anyone can change the RF shields and still say the cal is good.

[rf-loop]

What about a re-calibration? There is no way anyone can change the RF shields and still say the cal is good.

You  know or just believe?
I have repaired some of these SSA's  RF units and know something how they act. Circuit design is good and it is not like crap hobbyist build hassle what drift wildly even  if you jump on the floor. This construction is rock solid.

I do not know! I only believe and predict based my limited knowledge and some limited experience, it do not need new factory calibration table after this repair if it is done right. I keep this until some proofment with data that I'm wrong in this named case.

Of course, who ever do works inside SSA need know how to handle things in this SA. It is not at all everyman work, even when it looks quite simple. There is so many traps what may lead damage or drift or latent damage what will later become active failure (example EOS/ESD latent damages). Also board is mechanically very fragile. Also some filters on the board need care and all need keep clean. But handled right it do not drift with these parameters what are in calibration table. This machine is only up to 3GHz so it is not very difficult and critical.
Of course aluminium block dimensions must not change out from its dimensional tolerances.
If I change some mixer or example front end attenuator it need new calibration data table.

Totally other case is if equipment have valid official NIST traceable calibration certificate.
When the calibration laboratory set the seals and they are broken the calibration certificate is not valid anymore. It needs new cal certificate. (even if nothing is changed but still needs a new valid certificate.) This is done by making measurements in an approved calibration laboratory but typically not adjustments (exept if asked for example improve accuracy and paid or if some value have drifted over specs and if it can adjust. If not, then repair. If can not. Then to recycle or use without certificate for purposes what do not need cert added with warning label about situation)

So, if SA have fresh valid cal cert. It is perhaps wise to wait for this repair until the cal cert needs to be renewed. This avoids the extra cost since usually the official cal cert is not cheap.

[nctnico]

What about a re-calibration? There is no way anyone can change the RF shields and still say the cal is good.

You  know or just believe?
I have repaired some of these SSA's  RF units and know something how they act. Circuit design is good and it is not like crap hobbyist build hassle what drift wildly even  if you jump on the floor. This construction is rock solid.

I do not know! I only believe and predict based my limited knowledge and some limited experience, it do not need new factory calibration table after this repair if it is done right. I keep this until some proofment with data that I'm wrong in this named case.

Of course, who ever do works inside SSA need know how to handle things in this SA. It is not at all everyman work, even when it looks quite simple. There is so many traps what may lead damage or drift or latent damage what will later become active failure (example EOS/ESD latent damages). Also board is mechanically very fragile. Also some filters on the board need care and all need keep clean. But handled right it do not drift with these parameters what are in calibration table. This machine is only up to 3GHz so it is not very difficult and critical.
Of course aluminium block dimensions must not change out from its dimensional tolerances.
If I change some mixer or example front end attenuator it need new calibration data table.

TheSteve is right. After a repair you can't say the cal is still good without testing. The number of IFs in your statement above also implies that.

[rf-loop]

What about a re-calibration? There is no way anyone can change the RF shields and still say the cal is good.

You  know or just believe?
I have repaired some of these SSA's  RF units and know something how they act. Circuit design is good and it is not like crap hobbyist build hassle what drift wildly even  if you jump on the floor. This construction is rock solid.

I do not know! I only believe and predict based my limited knowledge and some limited experience, it do not need new factory calibration table after this repair if it is done right. I keep this until some proofment with data that I'm wrong in this named case.

Of course, who ever do works inside SSA need know how to handle things in this SA. It is not at all everyman work, even when it looks quite simple. There is so many traps what may lead damage or drift or latent damage what will later become active failure (example EOS/ESD latent damages). Also board is mechanically very fragile. Also some filters on the board need care and all need keep clean. But handled right it do not drift with these parameters what are in calibration table. This machine is only up to 3GHz so it is not very difficult and critical.
Of course aluminium block dimensions must not change out from its dimensional tolerances.
If I change some mixer or example front end attenuator it need new calibration data table.

TheSteve is right. After a repair you can't say the cal is still good without testing. The number of IFs in your statement above also implies that.

Of course normal lab practice.
Example what I have done is that before anything, some (quite lot of) important measurements and cross checks and results write down. After finished, check that same measurements give same result or changes are enough small. It is natural that all peoples do not have this possibilty to do enough reliable measurements. So, typically this is not like DIY work for Mr Everyman.

Situation is very different if equipment have valid calibration certificate. After works done this calibration certificate is waste paper. Even if nothing have changed but if seals are broken certificate is just toilet paper. Period.
Only way for this case is get new cal certificate from official calibration lab. If chek do not meet specs can not write certificate and then need first repair/run "factory calibration" what corrects changes.
But it is like that after this named repair it still is ok without need of full service calibration what produce new calibration parameters to SA internal cal table. But if it need valid NIST traceable cal certificate then it need this calibration check procedure for new certificate.  Calibration and calibration check for producing valid calibration certificate are not at all same. Some times it is hard ti find which one peoples are talking about.
Totally different case if any critical components are changed in repair. It can easy imagine of look example SA internal cal table what have quite lot of data. It can say that mostly in these kind of repairs need produce new calibration data doing full "factory calibration". Example I do not have things what is needed for this.

[rfspezi]

My SSA3021X replacement just arrived and i immediately checked if the input related spurs got better.
The replacement unit gives me -65,15 dB.
Hmm.... ok, so it's tight within the specified <-65 dBc - however Siglent leaves me with the bad feeling that the value will worthen again over time  

[GDK_ATL]

Did they return the same unit or is it a new one? I thought I read where units without the problem are showing the spur down around -72 dBc or so.

[rfspezi]

It‘s another unit with production date January 2018.

[Safar]

Hi,

One else SSA:

System info:
SW1: 1.2.8.5a
SW2: 20170512-1
SW3: 000000D1
HW: 07.03.00
Calibration: 2017-04-22

I don't have clean source so I fed it from SDG2042x (Surprisingly works at 110MHz  )

Slightly not in spec....  ~61..62dB

But I bought SSA from some seller on Ali, that even does not exist anymore (but just for 1400 USD shipped!), so I think have no any chance for change it on this case.  May be I'll check screw later.

I attach AVG 10 times also.

Edit: Add 1280MHz and 3180MHz screens. Almost the same result (62..63 dB). M2 marker just for noise floor. All markers link to AVG20 trace

[rfspezi]

I fear that the units within spec and produced lately will degrade over the next view months to end up beeing out of spec just as the units produced some time agoe?
As untreated aluminum will build up an isolating oxide layer, i expect shielding performance to degrade?
I think we should perform a spurious test regularely before warranty period ends.

[Safar]

I fear that the units within spec and produced lately will degrade over the next view months to end up beeing out of spec just as the units produced some time agoe?

May be but for now first production units better than new one.

And I saw rf-loop message that deleted now, but I answer about spur near 110 MHz on my trace - this is SDG product only. Very possible garbage from some digital part. Very unstable frequency. And it passes to 2 outputs even if it disabled. Need to find.

[rf-loop]

There is also available one solution. It can learn from Keysight who have solved this same problem.
I have never seen lot of Keysight owners who complain this. Or is it because they pay more than four times this price.
Solution can read here, page 7. Beginning of this page.
I will recommend this solution also for Siglent.

[rfspezi]

 

[Safar]

I will recommend this solution also for Siglent.

Yes, yes... I think that spec of next Siglent SSA will be at Keysight spec (Input related spurious < -60 dBc) 

[G0HZU]

If I assume that the Keysight spec is a generic spurious specification that includes harmonic spurious terms then this figure will be dominated by the 2HI spec of about +30dBm. This isn't a bad 2HI spec for a budget analyser and it's better than some very expensive R&S analysers at low frequencies. Generally, the 2HI spec will be poor at the low end of the frequency range (on a budget analyser) for various reasons and I'd expect the Siglent and the Keysight analyser to both be about the same here in terms of spurious free range for 2HI terms.

So be careful of what you are laughing at here

By contrast, the rejection performance (or lack of it) at about a 60MHz offset on the Siglent analyser is not good even at -70dBc. I still maintain that something isn't right. I did suspect the metalwork straight away but it might be only part of the problem. If I had one of these analysers I'd take it apart and try and improve the performance here.

[Performa01]

By contrast, the rejection performance (or lack of it) at about a 60MHz offset on the Siglent analyser is not good even at -70dBc. I still maintain that something isn't right. I did suspect the metalwork straight away but it might be only part of the problem. If I had one of these analysers I'd take it apart and try and improve the performance here.

You have voiced your concerns about cascading high order filters directly without any isolation between them quite a while back and this has also been my immediate thought when I saw the corresponding picture of the PCB. Interestingly, no one else has picked up on that topic so far, so I would like to recall this once again.

Even though my experience is with much lower frequencies only, I can safely state that stop band performance will suffer significantly and unwanted resonances will build up as soon as we connect resonant structures – be it matching networks or filters – with quality factors Q > 0.7 involved directly. These structures are designed for a specific characteristic impedance and will only work properly if there is a corresponding broadband termination on their inputs & outputs. The output of the 1st filter doesn’t provide a proper wideband termination for the input of the cascaded 2nd filter and the same is true for the input of the 2nd filter with regard to the output of the 1st one. Termination will be not good for the pass band and atrocious in the stop band.

Consequently, I’ve used bandpass diplexers whenever feasible – which is of course only feasible for low Q networks and we cannot mirror a high order filter shape with a simple LC structure. For high selective bandpass filters, I would consider a 6db attenuator or an active buffer, but as you’ve suggested, a simple series resistor might already help a lot in damping unwanted resonances.

[rf-loop]

By contrast, the rejection performance (or lack of it) at about a 60MHz offset on the Siglent analyser is not good even at -70dBc. I still maintain that something isn't right. I did suspect the metalwork straight away but it might be only part of the problem. If I had one of these analysers I'd take it apart and try and improve the performance here.

You have voiced your concerns about cascading high order filters directly without any isolation between them quite a while back and this has also been my immediate thought when I saw the corresponding picture of the PCB. Interestingly, no one else has picked up on that topic so far, so I would like to recall this once again.

Even though my experience is with much lower frequencies only, I can safely state that stop band performance will suffer significantly and unwanted resonances will build up as soon as we connect resonant structures – be it matching networks or filters – with quality factors Q > 0.7 involved directly. These structures are designed for a specific characteristic impedance and will only work properly if there is a corresponding broadband termination on their inputs & outputs. The output of the 1st filter doesn’t provide a proper wideband termination for the input of the cascaded 2nd filter and the same is true for the input of the 2nd filter with regard to the output of the 1st one. Termination will be not good for the pass band and atrocious in the stop band.

Consequently, I’ve used bandpass diplexers whenever feasible – which is of course only feasible for low Q networks and we cannot mirror a high order filter shape with a simple LC structure. For high selective bandpass filters, I would consider a 6db attenuator or an active buffer, but as you’ve suggested, a simple series resistor might already help a lot in damping unwanted resonances.

I an very interested about this (and other things also there inside)
But is it so that this can split to two separate roads.

How to make/mod its hardware better what it is designed to be (this is interesting)

How to return/repair units what have this problem to meet they original and designed performance or lack of  performace... how want think about. (this is - must)

[TurboTom]

If I recapitulate my experiments with my SSA3021X with the shields removed / loose and compare the observed figures with the machines that had reportedly been corrected by Siglent, I can only whole-heartedly agree with "G0HZU" that inaccurate metalwork of the shields can only be half the truth. Unfortunately, unless we'll get some high-res teardown photos of a recent production machine's RF PCB, we're only "poking around in the fog". My guess is that Siglent (had to) change(d) the circuitry/components that led to the problem. The workaroud may be improved RF damping by installing shields with RF/microwave absorbers (ferrite blocks/plates) in certain compartments.

Nobody who owns one of the affected models brave enough to tear it down and take photos of the RF PCB? The "warranty void sticker" can be removed without damage using wax paper, some warm air and patience. And with some care and common sense, there's no risk of damaging anything. I guess many members here on the forum would be grateful for that.

Cheers,
Thomas

[rf-loop]

I can only whole-heartedly agree with "G0HZU" that inaccurate metalwork of the shields can only be half the truth.

Cheers,
Thomas

But as far as I know reason is not inaccurate metal work.
(if you mean dimensions)

What I have understooded problem is material. Metal work supplier have changed/added some kind of different surface oxidation process. But as long as Siglent do not make details/explanation officially public we stay in some "fog".

Where we can see result of repaired SSA. Evidence they are repaired, where? Sorry but I doubt a bit.

But also we can of course speculate if they have changed some component, example "compatible" other manufacturer same componnet.
I well remember what they did some day with SDG1000 series awg. Compatible output amplifier was not really compatible in this special case. All looks like just compatible and pin compatible (other manufacturer "looks like compatible") but deep inside data sheet there was some small imperceptible thing...and result was disaster in this individual case.. The problem was only noticeable in some situations, but it was bad when it did.

When I have time I will teardown my SSA and make some experimentals with this aluminium block. perhaps I can somehow mimic different surface layer between PCB and Al..  perhaps not useful but it do not cost anything and then I can also strenghten my SSA input ESD protection. (btw, this is what they have also perhaps changed in Siglent for later production what was perhaps not in production some time ago. How much this affect performance in front end - I do not know before I have suitable components and then done it)

[RFDUK]

When I have time I will teardown my SSA and make some experimentals with this aluminium block. perhaps I can somehow mimic different surface layer between PCB and Al..  perhaps not useful but it do not cost anything and then I can also strenghten my SSA input ESD protection. (btw, this is what they have also perhaps changed in Siglent for later production what was perhaps not in production some time ago. How much this affect performance in front end - I do not know before I have suitable components and then done it)

Has there been an ESD weakness reported in the past that resulted in SSA hardware changes?

The 4dB noise floor difference between old and new instruments may be explained by a small fixed attenuator at the input socket introduced to improve ESD ruggedness.

My January 2018 instrument spur performance of -71dBC has remained consistent for 4 weeks now. It's kept in a fairly consistent 20 degree C environment though.

The previous comments on the -65dBC input related spurious specification and comparisons to more expensive instruments are very relevant when judging what is reasonable.
Better than -60dBC spec is reasonable for higher level inputs, but -65dBC is not too great for lower level spurs that result from poor SA design or implementation that could be avoided at quite low unit cost. This is present at any input frequency and at any input level.
-50dBC to -60dBC is a SA toy, -70dBC is looking 'reasonable'.

Better than -80dBC would be a reasonable design target without adding a great deal of unit cost.

An old 'economy' general purpose SA here of the 1990s, an HP 8591E measures >-85dBC on the final mixer image spurious.

I wonder what a low cost Rigol SA performance is on the final mixer image spurious?

[rf-loop]

The 4dB noise floor difference between old and new instruments may be explained by a small fixed attenuator at the input socket introduced to improve ESD ruggedness.

What attenuator and where?

There is not any extra attenuator inside SSA after input connector and before ESD - over voltage sensitive things. Not yesterday, not today or tomorrow as far as I know.

Input is very ESD and EOS sensitive, much more sensitive than older SA constructions where is typically mechanical input attenuator before anything. As example in HP859xE  what I have repaired/serviced many in older times. But, if user manually force attenuator to 0 (turning knob alone can not so it do not happend accidentally) and then if he do more and go to menu and turn DC block off (and this case user really need know what he is doing specially if he do noth, 0 atten and DC block off.  Then there is direct DC pathway and with this combination it can kill easy.

In Siglent, naturally there can not turn DC block off at all. (DC is forbidden to 1st GaAs switch.)

But it really need handle with care.
If bad happend, it is still quite easy to repair, so no need put to recycling of electronic waste.

[RFDUK]

A fixed 3dB input attenuator would be very good for improved ESD ruggedness on a SA input if the sensitivity degradation is acceptable.

ESD event has rise time of <1nS, so DC block not relevant here?

Very difficult to improve ESD ruggedness of sensitive GHz instrumentation.

[TurboTom]

Regarding ESD sensitivity of the SSA input, I guess it all depends on the particular RF switch MMIC that Siglent used in their design. AFAIK nobody so far was able to identify it (case marking 955C). When I received my unit, I spent some time (unsuccessful unfortunately) trying to identify it. Since it seems that several manufacturers offer such switches with improved ESD tolerance, maybe the situation isn't as troublesome as we may think. I don't want to be the guinea pig though and rather use to treat the instrument's input quite carefully.

Cheers,
Thomas

[rf-loop]

A fixed 3dB input attenuator would be very good for improved ESD ruggedness on a SA input if the sensitivity degradation is acceptable.

ESD event has rise time of <1nS, so DC block not relevant here?

Very difficult to improve ESD ruggedness of sensitive GHz instrumentation.

DC block and and ESD protection, they all are different things.
I did not at all mean anything about DC block related to ESD!
Only told it about  HP and then tell that in Siglent DC block can not turn off. (of course can not because it is not implemented but also reason why it can not implement)



Up to some GHz there is still some things what can do for some level esd protection.

If there is well over 500V (up to ^ and perhaps potentially well over 1A (short time) peak current available... what is not at all unusual... 3dB attenuator can not do much (but of course tiny bit more than nothing) - simple physics.

If use external attenuator, as example I recommend many times, and then take it away only when really need. Still I want note that do not think and believe or trust this is ESD/EOS protection. Still need be careful.

[rf-loop]

Since it seems that several manufacturers offer such switches with improved ESD tolerance, ....

Cheers,
Thomas

Afaik it is not reinforced and from well known manufacturer.

(exept if it is short time ago changed)

[Safar]

Why not use some external coaxial limiter for ESD protection?

[TurboTom]

Slightly OT: Please find attached a quick comparison of the Siglent and the Rigol DSA815 V02.04 input circuitry. In case of the Siglent, I (maybe erroneously) assumed that the MMIC RF switches must feature some internal ESD protection since the footprints for the external suppressor diodes (D31~D34) are left unpopulated.
It's quite a surprise how much effort Rigol put into the design of their recent DS815 frontend circuitry. Clearly visible, they placed there some RLC circuitry and four(!) suppressor devices all in parallel. This input should be rather rugged.

Cheers,
Thomas

[rf-loop]

Rigol is 1.5GHz and Siglent is 3.2GHz

But here R-S both noise floors 0-1.5GHz with 30, 100 and 300kHz RBW, P-Pk detector.

S: rf-loop, R: TurboTom





Of course this is not just first parts in front end but when I see this Rigol first what I think is ... why?
But I like to see Siglent front end how it is now. I still have some mutual imagine that they have changed some, just there.

[TurboTom]

From the plain figures, noise-wise the Rigol appears to be 10dB worse than the Siglent. But there is one little detail that may affect the relation somewhat: The Rigol DSA accepts 10dB higher signals at the mixer before producing significant distortion than the Siglent. This means, at the same signal level, you can run the Rigol with 10dB less attenuation than the Siglent which puts the noise level approximately on par. Of course, at very low signal levels, the Siglent is better off. Also, the Siglent SSA is the more modern machine with all the benefits of better semiconductors and the like. Anyway, this thread isn't covering the differences of the Rigol vs. Siglent spectrum analyzers, I just wanted to point out in my previous post that there still may be more questions than answers regarding the front-end designs.

Cheers,
Thomas

[RFDUK]

Quick update on our SSA3032X.

Several weeks on and the instrument performance on the problem spur has remained typical and stable at -71dBC.

I also measured this with the instrument coming from 12 hours in a +4 degree C environment too, immediately after switch on from cold and again -71dBC. Very happy.

[trevwhite]

I had a SIGLENT SSA3021X which suffered from the input spurious problem. I had bought the unit from Batronix and contacted them. They were brilliant and said they would get the unit repaired. I commented that I did not want it repaired because I believed the original unit was sent out faulty and I did not like the idea of someone opening the unit up and messing with it. I said I would prefer a replacement new unit. They said no problem. It arrived today.

This kind of service is great and makes me want to buy more from Batronix in the future. Big thumbs up to them for great after sales service.

Note I have not had chance to test the input spur yet but its a new unit.

[GDK_ATL]

Please let us know how it is.

I'm still trying to decide if it's worth returning my unit. If I do, it looks like it'll have to go to the Siglent facility in Ohio, as Saelig seems to want to pass the buck to them, instead of replacing the unit, which not only doesn't meet the spec, but was delivered with a loose part rattling around inside.

[tautech]

Please let us know how it is.

I'm still trying to decide if it's worth returning my unit. If I do, it looks like it'll have to go to the Siglent facility in Ohio, as Saelig seems to want to pass the buck to them, instead of replacing the unit, which not only doesn't meet the spec, but was delivered with a loose part rattling around inside.

Have it repaired ! Does it still rattle ?
The cause of that rattle needs be identified and reported to the production guys.

[GDK_ATL]

Well like I said, Saelig seems to think it's not their problem. It sounds like a loose nut rattling around. If it turns out the -65dBc spec can't really be met reliably even by newly manufactured units, then I'll probably just bite the bullet, void the warranty, and open the unit to fix the loose screw myself.

[tautech]

Well like I said, Saelig seems to think it's not their problem. It sounds like a loose nut rattling around. If it turns out the -65dBc spec can't really be met reliably even by newly manufactured units, then I'll probably just bite the bullet, void the warranty, and open the unit to fix the loose screw myself.

Please don't open it.
It's not Saelig's problem, it's Siglent's and yes, new units meet spec.

[rfspezi]

I had a SIGLENT SSA3021X which suffered from the input spurious problem. I had bought the unit from Batronix and contacted them. They were brilliant and said they would get the unit repaired. I commented that I did not want it repaired because I believed the original unit was sent out faulty and I did not like the idea of someone opening the unit up and messing with it. I said I would prefer a replacement new unit. They said no problem. It arrived today.

This kind of service is great and makes me want to buy more from Batronix in the future. Big thumbs up to them for great after sales service.

Note I have not had chance to test the input spur yet but its a new unit.

Just because it's new does not mean the spurious problem is gone.
I got a replacement unit that is fabricated in Jan.2018 and it has -65,9dBc which is only 0.9dB within spec. (@22°C)!
Although i wish the device did better, i keep the unit since i am fed up sending the device back and waiting for another "try".

[rf-loop]

I had a SIGLENT SSA3021X which suffered from the input spurious problem. I had bought the unit from Batronix and contacted them. They were brilliant and said they would get the unit repaired. I commented that I did not want it repaired because I believed the original unit was sent out faulty and I did not like the idea of someone opening the unit up and messing with it. I said I would prefer a replacement new unit. They said no problem. It arrived today.

This kind of service is great and makes me want to buy more from Batronix in the future. Big thumbs up to them for great after sales service.

Note I have not had chance to test the input spur yet but its a new unit.

Just because it's new does not mean the spurious problem is gone.
I got a replacement unit that is fabricated in Jan.2018 and it has -65,9dBc which is only 0.9dB within spec. (@22°C)!
Although i wish the device did better, i keep the unit since i am fed up sending the device back and waiting for another "try".

Why -60dBc specified input related spurious in comparable Keysight SA is not problem and price is lot of higher than Siglent (and not only this detail in specs).  Yes I know Siglent need be better - other ways it is bug, issue or problem.
 

[GDK_ATL]

Not sure what you're trying to say. Are you asking a question, or making a comment? Looks like maybe you are trying to say that the Keysight SA spec is only-60dBc so we have nothing to complain about with the Siglent SA. I didn't buy the Keysight unit, I bought the Siglent SA, so I'd like it to meet the published specs whether Keysight is better, worse, or whatever.

[RFDUK]

Agreed GDK.
Comparison with the generic input related spurious spec of -60dBC for 'budget' SA, Keysight, Rigol and the rest is not acknowledging that this spur is ALWAYS there at ANY input frequency. I'm sure Keysight wouldn't put their name on any SA product that did that.

An occasional input related spurious that just pops up at certain frequencies at -60dBC would not be nearly so problematic as this Siglent issue.

[RFDUK]

Another thing ... comparing to Keysight if we must ... how does a -51dBC spurious instrument (the second one delivered here), at any input frequency, get through final functional test at the factory. Again, doubt Keysight would have delivered that.

On a positive note, the Siglent SA is fine value for money and we like it very much!

[rf-loop]

Not sure what you're trying to say. Are you asking a question, or making a comment? Looks like maybe you are trying to say that the Keysight SA spec is only-60dBc so we have nothing to complain about with the Siglent SA. I didn't buy the Keysight unit, I bought the Siglent SA, so I'd like it to meet the published specs whether Keysight is better, worse, or whatever.

If your Siglent do not meet its specifications it need repair. If it meets specs (and this specification is hard limit, not "typical" value). < -65dBc measured using pure sinewave and mixer level -30dB etc.  If below this limit it is in specs and ok for this,  but this do not mean it is good or exellent in my mind. Relative to price....well..maybe...hmm...so-so.

[PP7BB]

Siglent.eu offers ssa3021x as new units with latest hardware installed (serial number above 60110). I wonder if it means that components have been changed or only aluminium block is properly manufactured...

[rf-loop]

Siglent.eu offers ssa3021x as new units with latest hardware installed (serial number above 60110). I wonder if it means that components have been changed or only aluminium block is properly manufactured...

What components need change?
All new SSA from (https://www.siglenteu.com/)  Siglent Hamburg stock  are now just ok. In new units in stock there is all made with good aluminium blocks.  "Wrong" aluminium blocs case is history. If one have previously purchased unit with this problem contact your sewller for arrage solution for repair it.  (this previous aluminium block error what was reason for very much too high some input rerlated spurious was made in subcontractor who made these "wrong" blocks.) 
(I do not know how it is with distributor Siglent.eu  but this case have nothing to do with serial number  60110)

What is this serial number 60110 thing? Yes I know but why they still keep this information what is 2 years old information - only for generate extra confusion.
This was old case when early manufactrured some units have problem in Tracking Generator. After this serial number all manufactured units have better TG and - this is totally history today.

Today new units may have less also fixed frequencies internal spurs and also input related spurs well inside sprecifications (and I have some experience with these new ones) Better what example my old unit is. My opinion is that better than never before.

If you think Siglent.eu sell some bad units when they show this offer price. It is not, Siglent set this offer. This offer have nothing to do with previous historical problems in some old manufactutring lots.  This offer price is set from Siglent officially and it is not only one distributor as example Siglent.eu. You can see also all other distributors (In Europe) who have updated prices have this SSA3021X (not 3032X) limited time  offer between 16.4. - 30.6.2018.  Same offer  can also see example in highly reputable Batronix.

[GDK_ATL]

I just saw this https://www.extremetech.com/electronics/268629-ftc-promises-legal-action-if-warranty-voiding-stickers-arent-fixed-soon today. I originally found that my brand new SSA3032X had some loose hardware rattling around inside. It also had a problem with out of limit spurs discussed elsewhere so I had to send it back for repair. I would have taken it apart to find out what was loose first, but fear of voiding the warranty kept me from doing it. Turned out I didn't have to worry. FTC says if it cost more than $5.00 the warranty can't be voided by removing a sticker and opening up a product!

[DonRon]

Hi to all!
ANd here is my experience with a "bad" unit:
Bought my SA december last year and my unit has the problem with the spurious response (only - 58 dBc).
So I asked the local dealer (Batronix) for an exchange unit. They were very helpul and asked Siglent to send a new unit. But Siglent denied and said they will repair the SA.
At first I was a little bit scared about this decision. Waiting patiently to get the unit back.
This week (after 5 weeks) I received my repaired SSA3021 and I immediately made some tests.
Works great now: spurios response is about -70 dBc and noise level is low. Seems to work a liitle bit better than some of the (new) exchange units several guys reported here.

So I am really happy now and a big thumbs up for Batronix!

Cheers,

Ronald

[GDK_ATL]

Same here. I just got my unit back a few days ago. Spur is now down 70 dBc.

One problem I'll just live with though: Occasionally, (I can't reliably reproduce it) when using the tracking generator, the TG will just stop generating a signal. Actually, it may still be generating a signal, but not in sync with the frequency sweep of the SA. I can't really tell. In any case, it acts as if the TG has stopped. Nothing I've been able to do will get it going again except turning the unit off and back on. Then it's fine. This is an infrequent occurrence so I'm just going to live with it.

[tautech]

Same here. I just got my unit back a few days ago. Spur is now down 70 dBc.

One problem I'll just live with though: Occasionally, (I can't reliably reproduce it) when using the tracking generator, the TG will just stop generating a signal. Actually, it may still be generating a signal, but not in sync with the frequency sweep of the SA. I can't really tell. In any case, it acts as if the TG has stopped. Nothing I've been able to do will get it going again except turning the unit off and back on. Then it's fine. This is an infrequent occurrence so I'm just going to live with it.

The latest FW apparently addresses this TG issue.
See here:
https://www.eevblog.com/forum/testgear/siglent-ssa3000x-spectrum-analyzers/msg1504198/#msg1504198

A couple of posts earlier I provide the FW link.