Author Topic: SIGLENT SSA3032X input related spurious  (Read 28339 times)

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Offline RFDUKTopic starter

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SIGLENT SSA3032X input related spurious
« on: November 22, 2017, 10:28:08 am »
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.
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Offline rf-loop

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Re: SIGLENT SSA3032X input related spurious
« Reply #1 on: November 22, 2017, 04:01:35 pm »
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
« Last Edit: November 22, 2017, 04:15:44 pm by rf-loop »
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Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #2 on: November 22, 2017, 08:04:53 pm »
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.
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Offline rf-loop

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Re: SIGLENT SSA3032X input related spurious
« Reply #3 on: November 23, 2017, 06:37:58 am »


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.
I drive a LEC (low el. consumption) BEV car. Smoke exhaust pipes - go to museum. In Finland quite all electric power is made using nuclear, wind, solar and water.

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Offline adamgreig

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Re: SIGLENT SSA3032X input related spurious
« Reply #4 on: November 23, 2017, 10:41:24 am »
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.

 
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Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #5 on: November 23, 2017, 05:35:26 pm »
Many thanks for the test result.

Looks like I need a replacement instrument.
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Offline G0HZU

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Re: SIGLENT SSA3032X input related spurious
« Reply #6 on: November 24, 2017, 10:36:33 pm »
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.
« Last Edit: November 24, 2017, 10:39:23 pm by G0HZU »
 
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Offline G0HZU

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Re: SIGLENT SSA3032X input related spurious
« Reply #7 on: November 24, 2017, 11:19:15 pm »
Quote
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.
« Last Edit: November 24, 2017, 11:23:50 pm by G0HZU »
 
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Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #8 on: November 25, 2017, 06:37:00 pm »
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.
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Offline rf-loop

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Re: SIGLENT SSA3032X input related spurious
« Reply #9 on: November 25, 2017, 08:10:02 pm »
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:
Quote
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.
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Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #10 on: November 25, 2017, 09:07:40 pm »
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!
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Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #11 on: December 30, 2017, 05:46:21 pm »
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?
« Last Edit: December 30, 2017, 05:51:20 pm by RFDUK »
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Offline Performa01

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Re: SIGLENT SSA3032X input related spurious
« Reply #12 on: December 31, 2017, 12:27:27 pm »
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…
 
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Offline TurboTom

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Re: SIGLENT SSA3032X input related spurious
« Reply #13 on: December 31, 2017, 06:51:52 pm »
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
 
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Offline cncjerry

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Re: SIGLENT SSA3032X input related spurious
« Reply #14 on: January 01, 2018, 08:54:49 am »
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.
 

Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #15 on: January 01, 2018, 09:54:06 am »
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.
« Last Edit: January 01, 2018, 09:57:38 am by RFDUK »
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Offline tautech

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Re: SIGLENT SSA3032X input related spurious
« Reply #16 on: January 01, 2018, 10:23:48 am »
 :-//
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.
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Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #17 on: January 01, 2018, 10:46:59 am »
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.
« Last Edit: January 01, 2018, 10:51:28 am by RFDUK »
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Offline nugglix

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Re: SIGLENT SSA3032X input related spurious
« Reply #18 on: January 01, 2018, 11:19:55 am »
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.
 
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Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #19 on: January 01, 2018, 11:36:21 am »
Thanks nugglix, it confirms the older ones a coming out consistently 5dB inside spec.
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Offline rf-loop

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Re: SIGLENT SSA3032X input related spurious
« Reply #20 on: January 01, 2018, 11:42:56 am »
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.
« Last Edit: January 01, 2018, 11:49:41 am by rf-loop »
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Offline tautech

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Re: SIGLENT SSA3032X input related spurious
« Reply #21 on: January 01, 2018, 11:56:17 am »
We can go witch hunting spurs all year.  :scared:
Still nothing at 60 MHz in either SSA.

FOI ~145 MHz @ -30 dBm

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Offline nctnico

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Re: SIGLENT SSA3032X input related spurious
« Reply #22 on: January 01, 2018, 12:01:24 pm »
Hint: 144.7-85.33=59.37
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #23 on: January 01, 2018, 12:06:57 pm »
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?
« Last Edit: January 01, 2018, 12:20:48 pm by RFDUK »
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Offline RFDUKTopic starter

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Re: SIGLENT SSA3032X input related spurious
« Reply #24 on: January 01, 2018, 12:31:31 pm »
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.

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