Siglent SSG3021X - testing feedback and comments

[TurboTom]

As promised before, I did a similar test with my newly acquired and repaired R&S (no, not Rigol&Siglent...  ) SM300 RF Signal generator, albeit at 100MHz instead of 200MHz (shouldn't make much of a difference in case of a full-range mixer approach) and here, the amplitude modulation (100MHz carrier @ -70dBm, amplitude modulation 0.1% @ 50Hz) results in both sidebands properly being present... I hope the forum software won't mess up attachment as it did many times before... whatsoever, curious if Rigol's Siglent's competitor will also only display a single sideband under these conditions...


Edit: P.S. It seems that the side bands at 22Hz offset are present on the SM300 as soon as modulation is enabled. Very strange... Noticed almost at the same time I pressed "Save" that I confused Rigol with Siglent 

P.P.S. In this measurement, I synced the SSA3000X to the 10MHz output of the SM300 since there is some noticable offset between the two reference oscillators. Next time I'll pull out my Rubidium Standard (RS???    )....

P.P.P.P.P.P.P.S. Did some more tests with the SM300 to exactly replicate the previous measurements and at 3GHz, yet with the SSA3000X as analyzer. In how far this affects the results vs. the SVA1032X (plus) is something I cannot comment on.

[noreply]

whatsoever, curious if Siglent's competitor will also only display a single sideband under these conditions...

@turbotom

Just to be clear the investigations with rf-loop were on the Rigol DSG815 - this IS Siglent's competitor.

I am yet to do SAME test on the Siglent.

I will use same references on the Sig Gen (100MHz) as well as the SVA like you did - this way we should have 3 devices to compare (the R&S included)
 

Hopefully post results tomorrow 

[rf-loop]

@rf-loop

Thank you for your feedback.

Yes long 'text' description of images can be confusing - I will try to be more structured in the future.

So to clarify some of your questions and comments;-

The 13dBm I refer to is ALWAYS the output level of the DSG815 RF output (N connector).

I chose this level because its the highest 'in calibration' level and it would be a good indicator of the 'worst case' harmonic response.

I can totally see your comment about harmonics as not being the RF generators Achilles heel - especially if they are 'clean' and well behaved (indication of a good and pure sinusoidal source) - so like you said - spurs and phase noise can be more critical aspects of performance.

Ok, I have re-run the test plots with the DSG815 output settings you suggested.

I have set the SVA to operate at its lowest noise floor for the given parameters - including switching 'on' the preamp - to even further lower the noise floor.

RBW and VBW both set at 1Hz

On the DSG815 the frequency was set at 200MHz

Signal Level at -70dBm for plots marked, and -80dBm for plots marked as well as -65dBm for plots marked.

Modulation AM - switched ON with 50Hz and modulation depth at 0.1%

On the resulting plot(s) you can see a 'spur' at marker 2

I did a few additional plots - to see variation - as we are so close to the noise floor and resolution limit - so each plot looks a little different due to noise and resolution limit.

I then did a wider span (still at -80dBm DSG815 output level) - to cover at least the 1st harmonic.

From the resultant plot - there was no noticeable harmonics as can be seen on the plot.

So I increased the DSG815 signal to -65dBm and did a plot - where the 1st harmonic was visible.

Hope the above additional plots prove useful.

Thanks rf-loop

Tnx.

Some comment.
You have selected 100Hz Span and you use 50Hz AM modulation what produce carrier - 50Hz (LSB) and carrier + 50Hz USB) sidebands. So if yout carrier is center your LSB and USB sides are just display left and right border. 200Hz (or 250Hz like @TT images later).  Siglent most narrow one FFT slice is 300Hz (with this setting) what is most small frequency hop when it is doing freq. hopping sweep in FFT mode. So with 300Hz Span or more narrow use same time and if even bit over 300Hz span then it use    same time for 301 - 600Hz Span. and so on. (in some point, I do not remember these hops are more wide and if I remember right there is least 3 "gears" how it is hopping. so or so it do not affect here so much but only for sweep time and some cosmetics some times just in these slices borders because there is not any ideal things like ideal filters etc, these exist only in students books)

But, now... why there is not at all visible these sidebands in your images but @TT images have and very clearly. These need be even partially visible because your carrier is mostly not center  and even if center half of sidebands shape need be visible due to 1Hz filter what have roughly 1:5 shape and 1Hz width is -3dB width.

Sidenote to some random readers. 10% AM mod depth (here with 50Hz modulating sinewave) need give sidebands level -26dBc and 1% mod depth -46dBc and 0.1%  naturally -66dBc. Of course generators modulation depth accuracy is questionable. If 0.1% is 0.2% it is 6dB difference in AM mod sidebands. (double % equals 6dB)
If look your noise floor and carrier 0.1% AM mod sidebands need be still easy detectable if all is ok. Now all is not ok.
Also it can see that Rigol huge noise floor around carrier (previous 200MHz images) is dropped also down as carrier level is dropped. Is it some form of PN - without deep investigations can not know. Guessing is form of entertainment art so... let it be.

So, where are these 50Hz AM mod sidebands?  Did you know why I ask -70dBm carrier

look friend @TT (TurboTom) images... where is noise level.

Make (no need image) small check... input example 100 or 200MHz from Generator A and generator B
Select 3Hz RBW (I know some reasons, specially if you use preamp) Set SA 0dB Att and quite narrow Span, example 3kHz and and ref line so that noise floor is near bottom and normal default detector as is ( and If I do this I do not use preamp). Set carrier near other side of display (because it is not important which one sideband you look and you can use more narrow Span for reduce waiting time).

Then start watching noise floor when you rise generator output starting from generator bottom, example  -143dBm (oh but these gens do not go so low so start anyhow generator bottom level) continue rising until generator out is ref level.
Look if both A and B generator give same result.
As can see @TT images noise floor near 100 and 200MHz carrier with signal levels -70 and -80dBm
compare with your images here.
For all testers. Even if you have super good or what ever external freq standard. These tests are  best to do without because all do not have and more importantly, no one know what these different ext references do to Siglent SA phasenoise independent of ext ref own phase noise. This whole case is extremely unclear. So for avoid unknown to come disturb.... freq accuracy is not question here at all. This is totally other thing. So why take risk and keep door open for unknown until there is enough evidence that ext ref really can not disrturb Siglent SA phase noise even if ext ref own PN is low. .

Try to find  how you can find AM mod .1% sidebands near carrier. Or is reason in generator what have so dirty near carrier.

[rf-loop]

As promised before, I did a similar test with my newly acquired and repaired R&S (no, not Rigol&Siglent...  ) SM300 RF Signal generator, albeit at 100MHz instead of 200MHz (shouldn't make much of a difference in case of a full-range mixer approach) and here, the amplitude modulation (100MHz carrier @ -70dBm, amplitude modulation 0.1% @ 50Hz) results in both sidebands properly being present... I hope the forum software won't mess up attachment as it did many times before... whatsoever, curious if Rigol's Siglent's competitor will also only display a single sideband under these conditions...


Edit: P.S. It seems that the side bands at 22Hz offset are present on the SM300 as soon as modulation is enabled. Very strange... Noticed almost at the same time I pressed "Save" that I confused Rigol with Siglent 

P.P.S. In this measurement, I synced the SSA3000X to the 10MHz output of the SM300 since there is some noticable offset between the two reference oscillators. Next time I'll pull out my Rubidium Standard (RS???    )....

P.P.P.P.P.P.P.S. Did some more tests with the SM300 to exactly replicate the previous measurements and at 3GHz, yet with the SSA3000X as analyzer. In how far this affects the results vs. the SVA1032X (plus) is something I cannot comment on.

It is good there is some third brand "reference" like R&S...

(what have specified as: SSB phase noise <-95 dBc (fc = 1 GHz, 20 kHz offset, 1 Hz measurement bandwidth)
<> Siglent 3000X Phase Noise : -110 dBc/ Hz @ 1 GHz , 20 kHz offset (typ.)
<> Rigol DSG800 Phase Noise : 100 kHz ≤ f ≤ 1.5 GHz < offset = 20 kHz, -105 dBc/Hz, < -112 dBc/Hz (typ.))


.... and so that different tests here by forum members have made "enough equally"  and even so that also tested with same kind of equipment (Sig SSA even when they may have small differences. One lab - all equal is not possible here)
If I'm in homeland home I can also do some tests but... now impossible. I can here only play with some bit better dual beam IR CO2 sensors and crap single beam ones and some poor and some bit better laser scatter small particle detectors and so on... for make some environmental datalogger...  when peoples come old it can see that time is really proportional(//)... more age and more fast it goes.  I do not know if time is speeding up or I'm going more slowly... or is it so that I try do more things than when I was younger.

[noreply]

@ rf-loop

My sincere apologies for the rather useless plots I made.

You must remember - although I understand basic RF principles - compared to you and turbotom I am a total 'noob' and this with the combination of my poor understanding of your instructions - I totally 'missed the boat' with my plots - as I completely missed the area of interest which should have been captured.

It was not until turbotom posted his plots / results for the R&S SM300 - that I realized my mistakes 

Thank you for your explanation rf-loop, I appreciate your efforts  especially when English is not your mother tongue 

To avoid any further confusion, I have made plots BOTH for the Rigol DSG815 and Siglent SSG3021X using identical parameters as turbotom did in his post above - Reply #25

Now we should have all three different manufactures for a quick comparison.

The respective plots are attached below with references to the turbotom's plots which they should mimic.

Hope that these are now sufficient - for some sensible commentary and discussion on the obtained results

Thanks @rf-loop, @turbotom 

[noreply]

I have been trying to do some simple EXT Modulation testing with the SSG today.

Unfortunately, I'm not having much luck - and getting some strange  observations.

This is what I am trying to do;-

I have a stereo encoder module.

The module simply creates a 19KHz FM stereo 'pilot' - and has LEFT and RIGHT audio inputs.

When 'powered-up' and output connected to SVA - you can clearly see the 19KHz pilot.

I then - on the SSG - want to set a Frequency of 108MHz with a level of 0dBm - this is no problem - and when 'set' and the RF output enabled on the SSG - I can clearly see the 108MHz carrier on the SVA at pretty much the 0dBm level.

Now I would like to connect the stereo encoders 'output' to the EXT Modulation INPUT (BNC) of the SSG.

This should modulate a 19KHz 'pilot' - the FM stereo pilot onto the 108MHz carrier.

Despite selecting the FM external modulation menu on the SSG and enabling the output - I cannot 'see' the 19KHz 'pilot' - it should be exactly 19KHz offset from the 108MHz carrier.

What am I doing wrong?

I presume that there is something wrong with my process 

I performed a similar test on the Rigol DSG815 and there was no problems - could clearly see the 19KHz 'pilot' next to the 108MHz carrier.

I even then got my portable FM radio - tuned to 108MHz and put close to the N connector input on the SVA - there was enough signal for me to hear the modulation test on the radio - in stereo.

My input to the stereo encoder module was audio from a YT video doing LEFT & RIGHT speaker testing - which was faithfully reproduced on the FM radio with the Rigo DSG815 acting as a FM Stereo TX.

So the proof of concept works on the Rigol DSG815 - but I cannot do same on the SSG

Any suggestions in configuring the SSG would be most welcome 

[xmo]

The external modulation input on the Siglent has an impedance of 50 ohms and is probably loading your source (the stereo encoder).

The Rigol has a selectable impedance and probably defaults to high impedance so it does not load down your source.

This is an example of why it's so hard to choose a complex product like a signal generator and why it's important to have detailed specifications from the manufacturer.

[xmo]

I got bitten by this issue myself.

I had a certain test that I usually ran using an Anritsu MG3642A generator.  It always worked fine.

One day I had to run the test and I had an Agilent ESG on the bench so I used that.  The test didn't work.

I learned the the external modulation input on the Anritsu is 600 ohms - which makes sense for an audio input, whereas the ESG has a 50 ohm input - something I would never have suspected.

So I checked and my R&S SML has a high Z input.  WTF?  Apparently, there isn't a standard.

Props to Rigol for giving you a choice of all three so their unit will work with any test setup you have been using.

[noreply]

@xmo

Thank you for your input.

Guess what?

You are 'spot-on' with your comments / observations

Who would have thought that Siglent - with all their wisdom - in the extremely 'modern' SSG3021X (compared to the 2015 vintage DSG800 series) would have made such a critical omission in their design - by not allowing the ability to 'set' the impedance of the external modulation input 

From this single omission - they just rendered the EXT input modulation capability pretty much useless for anyone wanting to use external modulation from professional audio and RF equipment.

I did notice the full capability of the Rigol DSG800 series in allowing the EXT modulation input impedance to be varied comprehensively - and it defaults to 600ohms, so I did not consciously 'look' for this in the Siglent SSG - but even if I did - its nowhere to be found.

I will ALWAYS stand to be corrected - because it is possible to be blinded by all the flashy menu options - and perhaps there is a secret menu - where  indeed you can set EXT Modulation Input impedance 

Well, for a guy who is willing to spend over $2K on a RF signal generator and is highly dependent on EXT modulation - for testing RF circuits (remember its sometimes easy to generate a complex modulation with an external source - like an SDR or a custom HW module like a stereo encoder - I am yet to test the RDS encoder) - the Siglent has just become a non contender 

I must admit - I like the modern interface AKA touch screen - but if the device is unable to do the 'job' interface is not important.

I hope that since we now have some noise floor measurements - someone can chime-in on how the Rigol performs against the Siglent?

A quick observation reveals Rigol has slightly better figures 

Finally, I hope that the EXT Modulation Input impedance is a 'forgotten' feature only in FW and does not need a HW revision to add the additional termination circuitry 

[noreply]

I have been doing a little bit of  because I was hoping that Siglent SSG3000X would be able to have 'high impedance' External Modulation Input.

So, I decided to have a look at the PUBLISHED SPECIFICATIONS for the SGS3000X series

- The DATASHEET
- The USER MANUAL

I Can confirm that in both of the above documents (SEE CAPTURED IMAGES) - Siglent confirms that there is only a 50 Ohm Input 


So, I decided to move UP to the SSG5000X Range - maybe there is a high impedance EXT Modulation Input on this more recent and more expensive offering - perhaps Siglend realized the omission on the SSG3000X range and made sure this did not happen on the 5000X range


So I decided to have a look at the PUBLISHED SPECIFICATIONS for the SGS5000X series

- The DATASHEET
- The USER MANUAL

BINGO!

The DATASHEET - sort of confirms that there IS a HIGH IMPEDANCE EXT Modulation Input (SEE CAPTURED IMAGES).

BUT

When looking at the USER MANUAL - IT clearly states that there is only a 50 Ohm EXT Modulation Input Impedance - NO SIGN of a 'high impedance' input as suggested in the DATASHEET 

OK - so even after moving to the over $5K product range of the SSG5000X - there is still confusion as to weather Siglent offers the same flexibility of selecting various impedances for the EXT Modulation Input as on the Rigol DSG800 Series - a much lower cost product - first released in 2015   


Message to Siglent

PLEASE

FIX the EXT Modulation Input on the SSG3000X range to support 50 Ohm, 600 Ohm and High Impedance (>1Mohm) selections, via the user interface.

PLEASE

Advise if this can be a FW 'fix' - or weather it requires modifications to internal circuitry.

Thank You

[xmo]

OK.  Here are a couple more thoughts for you about external modulation capability in signal generators.

Will the AM external modulation capability accept signals down to DC?  Why do you care?  If you can disable the generator's ALC and input DC to the external modulation input, you can create test configurations with external leveling. 

Guess which generator goes down to DC and which one doesn't.

How about external FM modulation down to DC?  Why do you care?  If you can FM modulate down to DC you can create test setups where the generator can function as a VCO.

Same question: which generator goes down to DC and which one doesn't?

So, as rf-loop pointed out, there's a lot more to selecting a signal generator the harmonic performance.

It would be really nice if there was a single resource with a comprehensive comparison of multiple signal generator models, their functions, features, and specs.

Speaking of specs, one spec rf-loop mentioned is phase noise.  I am really surprised that neither the Siglent or Rigol is really very good with the SSG at -110 and the DSG at -112.

[ that's dBc in a 1 Hz bandwidth at 20 kHz offset from a 1 GHZ carrier]

A look at some 20 year old generators:
Agilent ESG:  -116 dBc
Agilent ESG-DP: -134 dBc
R&S SML: -128 dBc

Why do you care?  For testing communications equipment you need a generator with low phase noise.  Here's what ANSI/TIA-603 has to say about signal generator requirements:

"The RF signal generator shall have the following characteristics:
...
c) Single sideband phase noise in a 1 Hz bandwidth of 135 dB below the carrier at 25 kHz offset from the carrier for frequencies of 500 MHz and lower.
For frequencies above 500 MHz, the phase noise shall be less than130 dB below the carrier at a frequency offset of 25 kHz from the carrier."

So neither of the subject generators would be suitable. 

BTW, you can't test the phase noise of either of these generators with the Siglent SSA because it's own phase noise is much higher than either generator.

For a tutorial on phase noise, see 'The Signal Path' #162

[rf-loop]

OK.  Here are a couple more thoughts for you about external modulation capability in signal generators.

Will the AM external modulation capability accept signals down to DC?  Why do you care?  If you can disable the generator's ALC and input DC to the external modulation input, you can create test configurations with external leveling. 

Guess which generator goes down to DC and which one doesn't.

How about external FM modulation down to DC?  Why do you care?  If you can FM modulate down to DC you can create test setups where the generator can function as a VCO.

Same question: which generator goes down to DC and which one doesn't?

So, as rf-loop pointed out, there's a lot more to selecting a signal generator the harmonic performance.

It would be really nice if there was a single resource with a comprehensive comparison of multiple signal generator models, their functions, features, and specs.

Speaking of specs, one spec rf-loop mentioned is phase noise.  I am really surprised that neither the Siglent or Rigol is really very good with the SSG at -110 and the DSG at -112.

[ that's dBc in a 1 Hz bandwidth at 20 kHz offset from a 1 GHZ carrier]

A look at some 20 year old generators:
Agilent ESG:  -116 dBc
Agilent ESG-DP: -134 dBc
R&S SML: -128 dBc

Why do you care?  For testing communications equipment you need a generator with low phase noise.  Here's what ANSI/TIA-603 has to say about signal generator requirements:

"The RF signal generator shall have the following characteristics:
...
c) Single sideband phase noise in a 1 Hz bandwidth of 135 dB below the carrier at 25 kHz offset from the carrier for frequencies of 500 MHz and lower.
For frequencies above 500 MHz, the phase noise shall be less than130 dB below the carrier at a frequency offset of 25 kHz from the carrier."

So neither of the subject generators would be suitable. 

BTW, you can't test the phase noise of either of these generators with the Siglent SSA because it's own phase noise is much higher than either generator.

For a tutorial on phase noise, see 'The Signal Path' #162

Least my old work horse HP8642B have AC and DC FM and also Ext Mod impedance is 600 ohm.
Only "bit" more expensive (in its time) and heavy than these low level modern Sig and Rig. There is warning label... for 2 person carry... but classified for "silent room" radio tests with low RF leakage. And of course.. ancient but what I trust this I use. Simply.
Years ago I tell some Siglent person that why they do not take time and download all old HP Journalls and study and learn something about design philosophy. It is not so that young engineer sit behind table and start desing new lab equipment. First need have three things. experience, experience and experience + knowledge. Some can learn from others. no need copy ancient things but many times there is tens of years experience and high knowledge behind old instruments design and lot of these are told for everyone if can read. There is totally free materials for this.  Electronics is different but test equipments basic usage have been so same tens of years that it is totally wood head who think external modulation input impedance is 50 ohm and period. Just because lack of enough experience and knowlege about anything from real world.

It must ask why these peoples are so lazy to find things and self learn - if can not ask. Yes I know partially one base reason it is in some country school system but it do not explain all...  do NOT think... listen teacher.

[noreply]

I just did some testing on the Rigol DSG815 - slapped together a stereo and RDS encoder - now I have a full 'broadcast quality' modulated FM signal that can be pumped into a suitable RF generator with a properly conditioned EXT Modulation input.

The Rigol did the job - took some pics and posted below - I guess to show Siglent to get their act together 

For about $100 worth of parts - you can now do FM receiver testing with Stereo and RDS - the flexibility of EXT Modulation Inputs should never be underestimated when buying a Sig Gen.

The Siglent SSG3021X has some very nice 'modern' features - but like rf-loop so eloquently put it - the 'young engineers' should take more care and LOOK CLOSELY at the OLD designs - there are countless hours of invaluable design experience which went into these products - so COPY the good features don't omit them.

The things I really liked about the Siglent SSG3021X - is the ability to set an 'offset' in the clock frequency - if you have a GSPDO - and can get atomic accuracy - its easy to calibrate the SSG within .01Hz

The other great feature is to be able to again set an 'offset' for signal level - another fantastic user feature - again if you have a more accurate reference - than you can 'dial' this up. Very handy when you have a lossy cable - and want to eliminate this from your signal loop calculations - just via this user menu 

Anyway, its always good to be able to 'learn' from the old masters - so perhaps @rf-loop could make a final comment on the noise figures posted above - as to comparing the Rigol to the Siglen - they are pretty close - but is there a winner?

[rf-loop]

The Siglent SSG3021X has some very nice 'modern' features - but like rf-loop so eloquently put it - the 'young engineers' should take more care and LOOK CLOSELY at the OLD designs - there are countless hours of invaluable design experience which went into these products - so COPY the good features don't omit them.

The things I really liked about the Siglent SSG3021X - is the ability to set an 'offset' in the clock frequency - if you have a GSPDO - and can get atomic accuracy - its easy to calibrate the SSG within .01Hz

The other great feature is to be able to again set an 'offset' for signal level - another fantastic user feature - again if you have a more accurate reference - than you can 'dial' this up. Very handy when you have a lossy cable - and want to eliminate this from your signal loop calculations - just via this user menu 

Anyway, its always good to be able to 'learn' from the old masters - so perhaps @rf-loop could make a final comment on the noise figures posted above - as to comparing the Rigol to the Siglen - they are pretty close - but is there a winner?

It is difficult with this EEVblog forum due to total mess with attached images. Example now I can not at all look these images where you make equal tests like @TT. Only small thumbnails are visible but when try look normal size image they are swapped with some other images. And original full size images are not in my cache so I can not see them anymore for further look.

But what I remember is that they are very close, some is tiny bit better in Rigol and some bit better in Siglent, if look these noise figures near carrier and also detected sidebands but perhaps there was one image what clearly show that Rigol AM mod level in 0.1% area was bit off. Overall Siglent low level AM mod levels looks bit better but also now only what I remember when I earlier look these.

Phase noise. SVA1032X is not at all right tool for this. First its own phase noise is problem for analyze these generators PN. This need Much better instrument. Also its PN is not fully specified. But if it is like SSA3000X then I know something about close carrier things and these can find also somehere in this forum, tested with my ex HP8644B.

We do not know (reading data sheet)  enough about SVA1000X  close carrier area PN until someone make some reliable tests (perhaps there also is but I have not looked).  Also its specified PN is not ok for characterize these generators PN.  In this test, related to phase noise we do not know if wagons are pushing or horses dragging. But there is some signs that these both are perhaps better than @TT 's  R&S SM300 (if he have not disturbed its or SSA noise figure with some extref).

Amplitude accuracy. But  +/- 1dB is normal good and typically it may be bit better.. Yes with offset can do correction if know used frequency and level true error but it can not make swept flatness better.  And true accurate level measurement over freq scale and over level scale is not simply and easy. There come very easy things like are in time nuts, freq nuts and voltage nuts. Example many peoples have "religion" that GPSDO and all is ok. This is partially one big bull and shit. It can be good but it can also be total trap if blind believe. Take one state of art DOCXO free run and compare short time errors.

With SSG5000X user can do his own flatness correction data table - but 5000 is other case.


Here attached part screen what I see now there instead of test result images.
Who hell have made this total mess in Forum system related to attacments please go back to kinderkard. btw, years it have worked ok. Why someone have started repair well working system and result is this <censored>.



as can see original images are swapped with other images (compare @noreply original post)
Where this error is hiding?

So I recommend attach images inside msg and not only like thumbnail after msg IF it may help or not..

[tv84]

Who hell have made this total mess in Forum system related to attacments please go back to kinderkard. btw, years it have worked ok. Why someone have started repair well working system and result is this <censored>.

Maybe it's time to stop patching FW and starting patching the forum. 

I have a feeling this all started with the new in-message images changes...   

[noreply]

@rf-loop , @tv84

I have edited the posts with messed-up images and resubmitted the images again - they appear to be ok - for now

Lets hope The Forum Admin staff are able to 'fix' this problem.

@rf-loop, perhaps you can now have a loser look at the plots if you wish to reexamine once again

Thank You

[rf-loop]

@rf-loop , @tv84

I have edited the posts with messed-up images and resubmitted the images again - they appear to be ok - for now

Lets hope The Forum Admin staff are able to 'fix' this problem.

@rf-loop, perhaps you can now have a loser look at the plots if you wish to reexamine once again

Thank You

still

"Siglent SSG3021X - 1st plot - direct comparison to turbotom PNG3 plot.png"

 give wrong image to me. It is some Siglent front panel picture.  This is now only missing image what I do not have.

More fun when I try download it I get file but when I try open it it tell that it can not open because it is not png image. After I change filetype to jpg I can open it and then there is same front panel image what also can see in forum if click this small image.

[tv84]

More fun when I try download it I get file but when I try open it it tell that it can not open because it is not png image. After I change filetype to jpg I can open it and then there is same front panel image what also can see in forum if click this small image.

   And no word from the admins...

[noreply]

@rf-loop , @tv84

I have edited the posts with messed-up images and resubmitted the images again - they appear to be ok - for now

Lets hope The Forum Admin staff are able to 'fix' this problem.

@rf-loop, perhaps you can now have a loser look at the plots if you wish to reexamine once again

Thank You

still

"Siglent SSG3021X - 1st plot - direct comparison to turbotom PNG3 plot.png"

 give wrong image to me. It is some Siglent front panel picture.  This is now only missing image what I do not have.

More fun when I try download it I get file but when I try open it it tell that it can not open because it is not png image. After I change filetype to jpg I can open it and then there is same front panel image what also can see in forum if click this small image.

The images seem to be OK for me - when I view now - after I reuploaded them.

Here are the Siglent images once again... hope they don't get messed-up 

Thanks @rf-loop

[rf-loop]

tnx
finally get all images. Later...some comment but of course with just some single test images can not say lot.

Also it looks like there is ExtRef used so it make things more questionable because we do not know how it affect other things than average frequency. So there is one or more unknown included. It affect more or less, lets hope less. But from images effect can not see so I name it added unknown. I do not even understand why it is used. If we look non harmonic spurs, sub harmonics and harmonics, phase noise, modulation, levels etc there really do not need External Reference for correct some small sub ppm offset in RF generator.  Then when we need very accurate freq and example so that all bab equipments use same reference, even if it is bit off or not then need ext ref. But, before use Ext Ref it is good to know how it MAY affect also other things than just freq average accuracy.



Oh and where is now Rigol DSG815 - 3rd plot - direct comparison to turbotom PNG8 plot.png (80.91 kB, 1023x600)
Name is there but image is Siglent 200MHz. (there is now 2x this same image in this same message where is Rigol and Siglent images together and there is now Rigol 1.5GHz missing when I look it now.)

[noreply]

Oh and where is now Rigol DSG815 - 3rd plot - direct comparison to turbotom PNG8 plot.png (80.91 kB, 1023x600)
Name is there but image is Siglent 200MHz. (there is now 2x this same image in this same message where is Rigol and Siglent images together and there is now Rigol 1.5GHz missing when I look it now.)

@rf-loop

I posted the 3 Rigol plots above - so should have both Siglent & Rigol now 

[noreply]

Today I decided to think 'outside the box' with regard to the Siglent SSG EXT Modulation Impedance being 'fixed' at 50 Ohm.

So how can we 'fix' this without breaking inside the SSG?

Simple solution is to build a 600 Ohm to 50 Ohm balun - this is a 12:1 ratio and can be build and tested - to provide a good impedance match.


If you are new to balun construction - here is a good guide ...

http://www.zl6qh.com/000225.html

- it describes an Antenna for RF transmission - hence large and bulky balun to handle the power - we don't need anything like this - so its only a guide in the design methodology - you can easily make your own 'small' mini balun for the use with the SSG.

It could even be mounted inside a 'box' with BNC In / Out connectors.


But the balun solution is a 'lossy' solution and may not be ideal for some type of low power modulated input signals.


Another approach is to have an active OP Amp where we can control the input impedance  - make it high and also the output impedance - make it 50 Ohm.

Being Lazy - at least today (it was like 30 Deg Celsius in London Today) - so I decided to use a 'off the shelve' module - in essence an OP Amp - preamp for phono cartridge pick-up.

Here I simply used one channel - to feed my high impedance (600 Ohm) output from the RDS / Stereo Encoder - and the output of the OP Amp was close to 50 Ohm - so this was connected directly to the SSG's EXT Modulation Input BNC connector.

Guess What?

After setting up the 108MHz at 0dBM and applying a the RDS / Stereo encoded signal on the EXT modulation BNC (through the OP Amp) - switched on my little FM radio - and Voilà - Music to my ears - everything working as expected.

This is not perfect and the 'audio level' is quite low - but it is proof of concept - we can 'fix' the EXT Modulation Input Impedance to accept High Impedance and not only 50 Ohm.

The best way to do this is to have Siglen make a FACTORY Module - a little 'box' with ACTIVE circuit - to be able to accept a BNC input and then provide a 50 Ohm output impedance to the SSG's EXT Modulation Input BNC connector.

This 'box' could have a 'switch' that could have 3 settings

- High Impedance > 1Mohm
- 600 Ohm Impedance
- 50 Ohm Impedance

This WILL WORK - and Siglent could even have an adjustable 'level' control to increase the amplitude of the modulated signal - a bonus feature - because sometimes a 'raw' modulation signal can be extremely low level - such as an output from an SDR where you are creating the output in software - but the SDR had limited output power.

So what did we achieve here?

Made a little experiment - proof of concept - that it is possible to 'fix' the Siglent SSG30231X factory 'omission' of a selectable impedance on the EXT Modulation Input.

If such a FACTORY DESIGNED module can be made promptly & supplied with EVERY SSG - FREE OF CHARGE - then the SSG once again can become a respectable instrument for day to day use where an EXT Modulation High Impedance Input is mandatory requirement.

If anyone associated with Siglent FACTORY (yes this could be you tautech    )  is reading this post - then PLEASE feel free to copy this suggestion and hopefully in two shakes of a tail (however the old saying goes ...) - we will have a little module to plug into out SSG that will fix this problem!

[noreply]

@turbotom , @rf-loop and anyone else ...


I have been looking at some 'old' RF signal Generators  and in particular their Specifications.

Its interesting to see how 'good' their specifications really are - considering their age

https://maximinstruments.com/pdf_files/MARCONI_2023_Datasheet.pdf

https://accusrc.com/product-Rohde-Schwarz-SM300-8340

https://www.testequipmentdepot.com/usedequipment/pdf/8642B.pdf


From a 'service' / calibration point of view the Marconi Instruments devices seem to be 'build-like-a tank' with a high degree of discrete components and a full BOM list and circuit diagrams in the user manuals - sorry did not see any teardown videos on the R&S SM300 or the HP 8642B as yet - but Dave did a good job at a Marconi Instruments 2025 (I hope I got the version correct - but they all share same structure)  teardown.

So, why is it that some 20 years later - with all the advances in analog semiconductor technologies and modern manufacturing techniques - there still is no COMPETATIVE offerings^(***) from the major manufactures - including China based - like Rigol and Siglen - to name just two of the most familiar here on this thread?

^(***)  Competitive offerings - in relation to a good condition 2nd hand specimen of one of the above listed, the price will often be BELOW the cost of an inferior specification 'new' device from all major manufacturers.

With this observation alone - I really don't see why anyone would buy a new RF Signal Generator - especially within the SUB $3000 range - when for this price alone you could score a 'old' high spec device which will beat anything on offer.

Any comments / discussion welcome

Yeah .. subject is a little 'off topic' but good to know the reason why we get what we get from the current manufactures within this price range

- does this mean that the current generation of products in this price range are OVERPRICED?
- if they were well 'below' the cost of a GOOD 2nd hand specimen of the 'older' generation
- would you still buy an 'oldie' or have the modern looking touch screen variant with 'peace of mind' that you don't need to fix-it yourself
- mind you if it still works after 20 years - it will work for another 3 (typically the new device warranty)

What do you think?

[rf-loop]

@turbotom , @rf-loop and anyone else ...


I have been looking at some 'old' RF signal Generators  and in particular their Specifications.

Its interesting to see how 'good' their specifications really are - considering their age

https://maximinstruments.com/pdf_files/MARCONI_2023_Datasheet.pdf

https://accusrc.com/product-Rohde-Schwarz-SM300-8340

https://www.testequipmentdepot.com/usedequipment/pdf/8642B.pdf


From a 'service' / calibration point of view the Marconi Instruments devices seem to be 'build-like-a tank' with a high degree of discrete components and a full BOM list and circuit diagrams in the user manuals - sorry did not see any teardown videos on the R&S SM300 or the HP 8642B as yet - but Dave did a good job at a Marconi Instruments 2025 (I hope I got the version correct - but they all share same structure)  teardown.

So, why is it that some 20 years later - with all the advances in analog semiconductor technologies and modern manufacturing techniques - there still is no COMPETATIVE offerings^(***) from the major manufactures - including China based - like Rigol and Siglen - to name just two of the most familiar here on this thread?

^(***)  Competitive offerings - in relation to a good condition 2nd hand specimen of one of the above listed, the price will often be BELOW the cost of an inferior specification 'new' device from all major manufacturers.

With this observation alone - I really don't see why anyone would buy a new RF Signal Generator - especially within the SUB $3000 range - when for this price alone you could score a 'old' high spec device which will beat anything on offer.

Any comments / discussion welcome

Yeah .. subject is a little 'off topic' but good to know the reason why we get what we get from the current manufactures within this price range

- does this mean that the current generation of products in this price range are OVERPRICED?
- if they were well 'below' the cost of a GOOD 2nd hand specimen of the 'older' generation
- would you still buy an 'oldie' or have the modern looking touch screen variant with 'peace of mind' that you don't need to fix-it yourself
- mind you if it still works after 20 years - it will work for another 3 (typically the new device warranty)

What do you think?

I have still my old work horse HP8642B.  It is quite good for normal conventional signals. Of course it can not do todays some important modulations and fast hopping etc. If you need QAM then game is ower with these oldies.
Why I use it. Because I trust it, it never fool me. Also it is overall in nice conditions. No need look more than this fron panel encoder. Bit different what these new generators have. Also if look these Rig and Sig. Put these to silent room and you can not do anything but close door and go home until they are cleaned away... 
But it is heavy!

Download HP web archives "HP Journal 1985 December" you can read lot of about HP8642B design. Just for one tiny detail. Even LCD display they have thinked and keep care that it do not emit RF noise around. You can think these modern Rig and Sig and they TFT panels. Take antenna and listen these. Aften then I ask do you want these jammers to silent room. No, they are not even made for yhis kind of serious use.
And yes I have also its precessor, totally different HP8642, mechanically like just out from factory. Its frequency walk and drift here and there but it have amazing low phase noise also due to its cavity resonator. 
Here:  (There can also find lot of older HP journals and more new HP journals and some of them have lot of knowledge and basics for learning also nice develop and design culture)

https://hpl.hp.com/hpjournal/pdfs/IssuePDFs/1985-12.pdf

For conventional signals and analog type modulations etc old Good quality generators are still very good and far over these Rig and Sig new ones signal quality and they are made like tank starting from front panel encoder ball bearings in some models and of course they all are optical encoders not switch type cheap or cheapest junk (yes in world there is also good switch type rotary encoders example from Grayhill but also they are not cheap=. Just like also older state of art class spectrum analyzers (what Tektronix have never made).
But, how to buy for get good one. It depends many things. Least it need real knowledge about these.

Of course after then there come more modern but still old generators example from HP-destroyedHP aka Agilent-Keysight and of course from Marconi-IFR-Aeroflex.
Also some R&S. But all these companies have made generators for different purposes and everyone have made also quite poor models. Really old analog time RTV repair service did not need other than some total junk Heathshit or if have lot of money some R&S or HP bottom class model. Buyer need know what he is buying and mostly these better ones, originally very expensive State Of Art class (higher than High End class) generators are not cheap even now but quite cheap - depending how you think. many tell that they are old and unreliable. Today these modern generators are made for up to some years longevity in light use. Old times thinking was very very different. I have owned lot of, example HP and some R&S,  gears what are not collected from waste loads and what have worked in heavy use 10 - 20 years and even still after then working in hobby like use lot of years and continuing. If also looks how complex these circuits are it is small miracle.


But back to original topic.
I have looked these some your test images. I leaved out these @TurboTom images due to reasons. First it is not Rigol Siglent compare. But nice reference here also other ways. One reason is that it goes to 3GHz and this image is not useful to compare 1.5GHz examples. Also it looks like there is something wrong in this individual test setup or generator. Last reason is also that if look data sheet it tell that this gen is in different more poor class with Phase Noise than Rig and Sig what are very close each others. Rigol datasheet tell it is tiny bit better but these images do not tell it or make this claim even questionable (image mark C).

What can see there is that Rigol AM modulation level is "out of order" but I have not checked if they have promised anything about mod depth accuracy.  Siglent looks more right ( image marks A). But also it need note that SA/SVA is near its limits here.
Rigol show, in these images,  one non harmonic spur marked B in image.   

Of course this kind of extremely tiny test can not at all tell anything like "which one is better". It need thousends times more tests and special tools for do all tests.  For normal use for use in this performance class what they are designed for they are like two berries without big differences. Perhaps one have bit better one thing and other bit better other thing. User need select what he like more and what are his need. Only individual user can + and -  with his own personal needs and what hive think more important than other thing.



Nearly like two strawberries, so different ones and still so same....

[noreply]

@rf-loop

Thank you for your observations / comments.

Yes, the simple test plots are not anywhere appropriate to draw conclusions of which device is 'better' - like you said there are numerous tests that need to be performed for a true head-to-head and then under 'controlled' conditions with a high capability analyzer - not one like the SVA used here -  which is already operating at its limits.

Nevertheless - these simple tests at least show that BOTH instruments are in the 'same class' - what is / was intended when Siglent Released their SSG to compete with the Rigol DSG800 series.

What probably matters more for the forum audience - is the 'value for money' when comparing Rigol to Siglent offerings.

Here, I feel there is significant opportunity to harness some sales on appropriate price positioning and marketing.

I would certainly buy a 3.6GHz DSG - with its small compact size at a lower cost than the equivalent Siglent 3.2GHz offering.

But there will always be the desire for some to acquire good specimen of an 'oldie' - when size and interface dos not matter - but only its capability, they will be better value always.

Your 'off topic' insights are most welcome - its great to hear such valuable observations - and truly appreciate the 'old school' engineering which prevailed in those days. Products were build to last, commercial aspirations were secondary. Today its the reverse - products are built to a price , performance comes second.