Author Topic: Siglent SSG3021X - testing feedback and comments  (Read 6438 times)

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Offline noreplyTopic starter

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Siglent SSG3021X - testing feedback and comments
« on: July 21, 2020, 10:56:56 pm »
Great new for me today – the Siglent SSG3021X arrived.

So now we can literally do a ‘head-to-head’ comparison with a less expensive rival – the RIgol DSG 800 series.


Initial Notable Differences


Size comparison is HUGE (the Siglent is huge) – see the attached photos.


Fan Noise – significantly higher level than the Rigol


Touch screen - +1 for Siglent – I like this feature – it’s very convenient compared to key entry alone


Control panel layout – Rigol is very compact because the Rigol is a small device so needs to be compact.


If you have ‘big’ fingers – then you must take care – the Siglent keypad has significantly more ‘real estate’ – so better suited for people with big thumbs.



Frequency Check


The Rigol – out of the box has excellent frequency ACCURACY and well within the STABILITY of 2ppm specification at 25 deg Celsius – within the range of 0 to 50 deg Celsius.


Interesting observation BOTH Siglent and Rigol do not provide a ‘specifications page’ inside their respective user manuals.

I guess they assume you are past this stage – where you keep referring to the specifications  NOT!


I think they SHOULD ALWAYS have a specifications page INCLUDED in your purchase – yeah you will say its online – sure – but I want it with the product – because it saves me 1 microsecond fafing around on the internet – something I don’t need to do if included  :P


So, after fafing around on the internet looking up the Specifications for the Siglent – I can confirm that it’s also within the Frequency STABILITY figure
 

– but WAY off in Frequency accuracy compared to the GPSDO 10MHz clock and also marginally worse than Rigol’s ACCURACY – also out of the box – no 'user' calibration.


Interesting to see that the Siglent - has menu function to 'tune' clock offset - nice to have - and possibly why they need it is because 'out of the box' Siglent has worse Frequency ACCURACY than the competitive Rigol.




BOTH instruments at room temperature (21 deg C) and ‘warmed-up for over 60 minutes.


Siglent Frequency Accuracy is: +0.95769Hz above the 10.000 000 00 MHz reference from GPSDO 10MHz source.

Rigol Frequency Accuracy was: +0.71581 Hz above the 10.000 000 00 MHz reference from GPSDO 10MHz source.


So it depends how much of a pencil neck you happen to be – like for like the RIGOL wins!

   

RF Signal Amplitude accuracy


At 10MHz and 0dBm output – the Siglent shows a level of -0.06dBm – hovering to 0.0 at times – this is extremely good. (see: siglent 0dbm.png)


BUT


When you think about it for a minute – you cannot trust this figure – because there is a N to N connection cable in the signal path.


I cannot believe that there is ZERO or close to zero (-0.06dBm) loss for the cable – even at 10MHZ this does not sound correct.


The Rigol shows -0.12 dBm at the same settings and conditions – I guess I am likely to believe the slightly higher figure better. (see: rigol 0dbm.png)


But BOTH devices have excellent attenuation level accuracy at 10MHz and 0dBm RF signal.




Harmonics


Firs we need to qualify some things as Rigol and Siglent have different ‘in spec’ calibration levels.


Rigol MAX output level in dBm within Calibration Specification is +13dBm


Siglent MAX output level in dBm within Calibration Specification is +13dBm - but device allows +17dBm without any UNCAL warning @ 10MHz


So for a like for like comparison meaningful values are up to +13dBm


I measured the respective harmonic levels at 13dBm for BOTH devices



At +13dBm – Rigol has no notable harmonics above -38.75dBm (see: rigol 13dbm harmonics.png)


At +13dBm – Siglent has notable Harmonics 1st harmonic is -19.57dBm – no notable 2nd / 3rd harmonics visible below 38.81dBm (see: siglent +13dBm harmonics.png)


I did not bother looking below this ‘floor level’ of the settings I used in the SVA



Rigol is a clear winner with regard to harmonics!



Please note - all of the above measurements and observations are 'quick' initial 'hands-on' testing - to give an indication where the respective instruments stand when comparing side-by-side.
It is not a precise 'test-lab' review - at least not at this time.
I can confirm that the Frequency Accuracy test has been performed with a 'test lab' quality frequency source - a GPSDO with a 10MHz reference.



More to come soon ...   ;)
« Last Edit: July 21, 2020, 11:19:21 pm by noreply »
 
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Offline rf-loop

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #1 on: July 22, 2020, 12:37:32 am »
You must use same MIXER level instead of same Input connector level! 

ETA: Sorry, it was my mistake when I "too quickly" look images and text about  levels used. Even now I do not understand what make me think that you used different SA mixer levels (what is naturally very important when try characterize  DUT's harmonics so that DUT harmonics are not messed too much with SA produced harmonics) .. Of course when I look now again I can not see any reason why I make this mistake.



 
« Last Edit: July 23, 2020, 01:24:03 pm by rf-loop »
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Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #2 on: July 22, 2020, 03:02:47 am »
You must use same MIXER level instead of same Input connector level!  |O

Thanks for dropping by this thread rf-loop.

I'm not sure what you were referring to with your comment?

If it relates to one of the screen photos on the Siglent SSG - the +17dbm was not the level used in the harmonics testing (both the Siglent and Rigol were tested with +13dBm) - I just put-up this picture because the SSG allowed to 'set' the +17dBm - despite the specifications stating that only a maximum level +13dBm is acceptable without 'triggering' an UNCAL warning.

Interesting thing is that anything ABOVE +17dBm will trigger an UNCAL warning message.

You can physically 'set' output level to a max of +20dBm

The Rigol will allow +20dBm also - but it will issue a UNCAL warning for any levels above +13dBm - its specified value in the specifications.


I would have expected the Siglent to also issue an UNCAL warning at the +13dBm value as described in the specifications - instead of the +17dBm  :-\

« Last Edit: July 22, 2020, 03:54:42 am by noreply »
 

Online tautech

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #3 on: July 22, 2020, 03:16:17 am »

There's a problem with this SSG3021X measurement.
First harmonic doesn't meet spec as it should be 30dB+ down.


SSG3021X 10 MHz 10dB using Siglent 6GHz N-N cable connected to SVA1032X in FFT mode with settings to reveal the 4th harmonic.
« Last Edit: July 23, 2020, 09:12:38 am by tautech »
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Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #4 on: July 22, 2020, 03:49:04 am »

LF mixer vs RF mixer so to compare apples with apples not some artificial oranges vs apples.
User error.

Anyways, why compare harmonics between 2 RF gens @ 10 MHz when this is way down in ARB frequencies.  :-//

What makes you think that LF was used in EITHER of the devices during the testing?


10MHz was leftover from Frequency check - why not check the ARB levels as well as the GHz levels - this device is specified to work at 10MHz - so why cant it be tested there?

The day is long - so plenty of time to test the GHz

Nobody is selling apples here - we are simply trying to get some measurements - rather than play with some buttons  :P

 

Online TurboTom

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #5 on: July 22, 2020, 11:37:40 am »
Thanks @noreply for your effort! It's good to see a direct comparison of the two current "decent" low-end SG contenders.

I may add in some data of an R&S SM300 soon since I got lucky (okay, it's up to be found out how much so...  ;)) on putting an offer on a defective one (as it seems, the well-known PA fault hit again), so if the repair turns out successful, I should soon be a proud owner of a vector signal generator for round about 600EUR (of which almost one third went for shipping... :'(). In contrary to Rigol's and Siglent's designs, R&S went for a full-range mixer approach.

I'm very curious how well an almost twenty years old design (also rather low-cost at its time) compares to today's budgetary instruments.
« Last Edit: July 22, 2020, 09:11:14 pm by TurboTom »
 

Online tv84

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #6 on: July 22, 2020, 11:48:18 am »
Generators Wars!  :box:
 

Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #7 on: July 22, 2020, 05:10:29 pm »
Hello tautech / Rob,

I want to deliver an important message – but at the same time do not want you to misinterpret or see this message as a negative or personal ‘dig’ at you.

THIS IS NOT ITS PURPOSE and I preface my message with this note especially to make it clear to you that my intentions are honourable and hopefully helpful for you and the community at EEVbog.

I have been an active member on this forum for a relatively short period of time.

During this time I enjoyed making almost 200 posts – it’s nice to be able to learn from others and at the same time share your knowledge and observations.

You must have been on this forum much longer – with almost 18600 posts.

During my short period here, I noticed that you tend to ‘pop-up’ in just about every thread.

Occasionally – you ‘chime-in’ to clarify an ‘open question’ – but most of the time you simply ‘chime-in’ with a comment or observation which has absolutely no value to the thread – but rather than help (which I am sure you want to do) – this type of uninvited ‘chime-in’ does more damage than good.


If you are still with me to this point and not getting a little ‘pissed-off’ – then that’s great – because I wanted you to remember my preface remark – my intentions are honourable and I truly believe that you are a ‘good bloke’ – who’s intentions are also honourable.


Again, this is not intended as a personal ‘dig’ at you – but an observation – from someone ‘new’ – so hopefully this fresh input will help you be more ‘in-tune’ because sometimes – after 18600 posts you can lose perspective and purpose which I think you have.


My self-imposed forum etiquette is simple.

If I find an interesting topic and decide to ‘read’ some posts, I don’t automatically have a desire or need or compulsion to make a comment. I will only make a comment if I feel it will ADD something POSITIVE to the subject under discussion.

Or, same logic, ask a question – only if it the answer will ADD something positive to the subject under discussion.

OK, now we have some self-imposed guidelines which I like to follow.


Now, let’s have a look at how ‘you appear’ to someone like me (and most likely many many others – who simply choose not to give you feedback) in the type of forum posts you make.


I started this new thread – as a point of focus for anyone interested in the Siglent SSG3021X RF Signal Generator.

I have been very fortunate to be given the opportunity to review this model – for myself – on a sale or return basis.

I could easily just spend a few days – doing my own non structured testing – a bit here , a bit there, check this, check that … until I have a good feel of the instruments performance.

If I like it – I will BUY it – the end!

But rather than go through this ‘privately’ I decided to do this ‘publicly’ – so maybe someone else on this forum could benefit – because they have not been fortunate enough in having a sale or return offer.

My review is not a ‘professional’ laboratory review – with high end test equipment stressing every aspect of the device under test – it’s far from it!

But despite this – I think it’s still going to be useful to many people – who simply want to ‘check it out’ – without the formal methodology of a professional testing lab.

So, I get the device unpacked and start my observations and testing.

At the same time I post my results in this thread – clearly stating in the end – more to come soon …


Shortly after, I am blessed with a well-respected senior forum member rf-loop who ‘chimed-in’ with a comment.

Upon reading the comment – I could not see or understand what rf-loop was trying to warn me about?

Perhaps I did something wrong in my test, or presented some data incorrectly?

Whatever it was – the fact that a respected forum member with far more experience than me (with a name rf-loop – you need to pay attention ;) ) chimed-in with a warning – made me think and check my post.

So I responded to rf-loop – trying to get some more insight in the meaning of his post – but using some etiquette at the same time and not being rude – by NOT responding with a comment like ‘what’s your problem mate?’ – instead I restated some observations and clarified some photos – just in case rf-loop misinterpreted something before making his comment to me.

Shortly after my response to rf-loop – you ‘chime-in’

BUT, instead of trying to be helpful – and using etiquette – you simply make a snide remark which in my opinion is clearly offensive and if that’s not enough, you then finish with a ‘slap on the face’  with another two remarks – more ‘slaps’ for each cheek   :palm:

Just in case you can’t see what I am talking about …

Quote
LF mixer vs RF mixer so to compare apples with apples not some artificial oranges vs apples.
User error.

Anyways, why compare harmonics between 2 RF gens @ 10 MHz when this is way down in ARB frequencies.

The proper response would be …

I think rf-loop may be thinking that you are using LF input on the Rigol and RF input on the Siglent – hence – any harmonic tests may not be accurate as different mixes are in play.

But instead you ‘offend’ by stating …

Quote
compare apples with apples not some artificial oranges vs apples.


Then add another …

Quote
User error.



And if that’s not enough – yet another (for the kill) ..


Quote
Anyways, why compare harmonics between 2 RF gens @ 10 MHz when this is way down in ARB frequencies.



So, rather than come back at you– with my now angry self – and make a rude response, I choose to be polite and in a tong-in-cheek manner respond with a comment that I know will paint you into a corner – making it difficult for you to continue with more offensive comments.


Quote
What makes you think that LF was used in EITHER of the devices during the testing?


10MHz was leftover from Frequency check - why not check the ARB levels as well as the GHz levels - this device is specified to work at 10MHz - so why cant it be tested there?

The day is long - so plenty of time to test the GHz

Nobody is selling apples here - we are simply trying to get some measurements - rather than play with some buttons  :P


Shortly after, you respond with …

Quote
Maybe my mistake on reading the DSG 800 display, sorry I'll butt out for now.
Please carry on.


Here is where I have to PAUSE – because – it is at this point that I can be of most help to you.


Let’s look closely at your response …

Maybe my mistake on reading the DSG 800 display,



You must of taken time – to ‘study’ all the information (which has not changed – been in front of you all the time) and now correctly identified what possibly rf-loop could have mistaken.

Here you could have clearly – pointed this out to me IN THE FIRST INSTANCE – alerting me to the possible mistake rf-loop made, but instead you choose to ‘snipe’ and try to score points!


Lets look at the second part of your response ...

sorry I'll butt out for now.


Now – you clearly see that you made a mistake – and PROPS TO YOU – you apologized ‘in small caps’ – a simple ‘sorry

You then – before the ink has dried on the ‘sorry’ remark - make another comment …


I'll butt out for now.


Here you clearly acknowledge that you HAVE ‘butted-in’ – in a subject that possibly did  not need your input i.e. you could have just let rf-loop reply (if he chooses) by himself.


And, wait for it, you state ..


for now.


 :palm:

This once again , clearly indicated that YOU reserve the right to come back and make more uninvited remarks!


Finally, if the above is already not enough indication of your demeanor, you go on to say …


Please carry on.



As if nothing has happened – nothing – and most importantly it’s like ‘permission’ to continue.

Possibly a subconscious remark – possibly knowing (subconsciously) that the above comments did cause offence and perhaps the original poster (me) might not want to continue – so your subconscious tries to validate itself  ‘please continue’ and just ignores what happened  :palm:


OK .. I finished  :popcorn:




Now we come to the most important part of this whole post / message to you.



Again I must clarify – all of my comments have good intentions behind them  – there is no malice – I am doing this publicly rather via a PM because  I don’t think there is anything here which is of a ‘private nature’ because everyone can benefit from this observation / comments – not just you.


1.   You need to take time – read the post IN DETAIL – don’t skim through and just look out for the name ‘Siglent’, decide if there is an implied ‘invitation’ for other members to ‘chime-in’ – if not then don’t do it just for the sake of increasing your forum posts counter.

2.   If there is good reason and an implied permission to ‘chime-in’ – do this with etiquette – don’t make tong-in-cheek-remarks (we all do it sometimes – but you need to refrain from this) and most importantly try to be helpful to the post in question , don’t simply make an unrelated remark – because this , believe it or not,  will ‘offend’ (subconsciously) most of the time.

3.   Please don’t wave your ‘distributor cap’ – this means don’t talk about any products , prices, features, new models, or ANYTHING ELSE relating to your business. Your only contribution to the post you respond to should be from ‘Rob’ the knowledgeable person and NOT ‘Rob’ the Siglent Distributor. THIS IS THE MOST IMPORTANT ‘TIP’ – because if you do this – its highly likely all of your small nit-picking offensive remarks will disappear in the process – because most of them are often related to ‘Rob’ the Siglent Distributor and most likely not ‘Rob’ the knowledgeable person.

4.   If someone ASKS a specific question – to you directly – in the post – inviting your input, do this with care – ONLY answer the question!, don’t add additional information, don’t make judgements , don’t make side comments – unless specifically asked to do this.



I have tried to cover a very difficult subject in this post – the message is definitely up there in the ‘text’ – I tried my best (without writing a detailed essay - although this is a long post) – to highlight the most important aspects.

I used your reply to me – in THIS post as a great example (I am sure there are many others in the 18600 posts you made within this forum) –  to highlight how a simple, what you think is a helpful reply, is in fact destructive and offensive instead.

I hope the above notes give you more insight to your – most likely subconscious -  behaviour in the hope that it will HELP you make more meaningful posts & contributions to the forum in the immediate future.

Please once again don’t take offence Rob – we all love you tautech, BUT you need to be informed of your forum etiquette shortcomings – all for the benefit of the members here.


Take Care and Be Safe
 
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Online TurboTom

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #8 on: July 23, 2020, 12:21:25 pm »
Tautech, IMO modifying a post in a way to completely change its contents, especially if it had been referred to afterwards, is at least questionable. But I'm not the one to argue about that.

Yet, your modified contents is not exactly correct either:


There's a problem with this SSG3021X measurement.
First harmonic doesn't meet spec as it should be 30dB+ down.


SSG3021X 10 MHz 10dB using Siglent 6GHz N-N cable connected to SVA1032X in FFT mode with settings to reveal the 4th harmonic.

It's true, the absolute level of the second harmonic in @noreply's measurement is just shy of -30dBm, but the relevant figure is the damping of the harmonic vs. the carrier, which in the aforementioned measurement is at almost +13dBm. Hence, the second harmonic is close to -42.5dBc which is very well within spec. I'ld say the measurement that @noreply did is completely valid.
 

Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #9 on: July 23, 2020, 01:32:42 pm »
I tried to reproduce your recent harmonics plot – using same settings as shown on your screen capture – well at least the ones I can see as shown on the captured plot you posted.

First observation


I tried hard to be able to have ‘same’ plot settings and at the same time for the markers to show ‘true’ dBm readings – specifically as shown on your plot.

Unfortunately I was unable to reproduce this.

Can you PLEASE advise – and possibly show (maybe screen capture) ALL of your settings?

When I applied the 10dBm ref – I was unable to get a ‘true’ direct dBm reading on the markers.

The 10dBm was ‘added’ to the measurements of the markers as seen on the screen capture I made.

I guess this is not going to alter the result – we simply subtract 10dBm from the marker readings to get a ‘true’ reading.


However I am puzzled at how you managed to get ‘true’ marker readings whilst still having the 10dBm ref set?


Once again please provide me with ALL the setting – so I can reproduce the harmonics response EXACTLY as you made – to have identical scaling settings – so our respective markers will have same initial conditions.

After all , we have the same HW – so this should be simple.


Second observation


Once again, I was having problems in getting the SVA’s noise floor as low as you did.

I noted the EXACT same  BW settings – can see this from my plot.

I also used the EXACT same frequency sweep settings – can see this on the plot.

And as a quick check the sweep time was EXACTLY same of 245.775 seconds – just like your plot.


So, can you please help me get in getting the extra -10dBm of noise floor?


I guess this has something to do with the 10dBm Ref – it ‘shifts’ the whole ‘plot’ by 10dBm.

Once again – it would be nice if I can share you exact setup – so can fully reproduce SAME conditions for the Harmonics test.



Third observation


My frequency on the SSG was set to 10MHz.

The ‘true’ frequency from the SSG was actually 10.95769 MHz – despite this my SVA did not show ‘true’ frequency of  the SSG.

The SVA is not capable (possible FW bug) – or it simply is unable to do accurate math's on a wide span when using markers?


This is a known behaviour – not just happening here.


However – looking at your screen capture plots – I can see you have ‘exact’ 10MHz clock.


This would be an exceptional achievement – given the problem I and possibly others have experienced with accurate frequency readings on the SVA with wide frequency span when using markers.

But – a closer look at your plot reveals an external REF – so I presume you ‘locked’ the SSG to the SVA or just provided an external 10MHz reference to both instruments?


I am not an expert on the internal signal processing of the SSG and SVA and the possible effects on harmonics – when ‘external’ frequency sources are used?


I guess for the sake of 'like–for–like' – maybe external references should not be used?



Final observation



The harmonic frequency response I posted for the Rigol DSG815 was at its calibration limit – that of 13dBm (same level and limit as the SSG)


The plot you just posted – to compare the Siglent SSG3021X harmonic response was NOT to a 13dBm level – it was plotted to a 10dBm level.

As you know – even using your own expression – this is not ‘apples-to-apples’ is it not?


So I took the liberty to plot BOTH the 10dBm and the 13dBM responses – they are attached below.



I look forward to your screen shot instructions as to the ‘exact’ same settings as discussed above – so I can reproduce your noise floor and the ‘true’ marker readings and re-run the harmonic responses again.



Thanks tautech
« Last Edit: July 23, 2020, 01:38:20 pm by noreply »
 

Offline rf-loop

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #10 on: July 23, 2020, 02:11:55 pm »

There's a problem with this SSG3021X measurement.
First harmonic doesn't meet spec as it should be 30dB+ down.


SSG3021X 10 MHz 10dB using Siglent 6GHz N-N cable connected to SVA1032X in FFT mode with settings to reveal the 4th harmonic.

I can not see any problem in @noreply test image.

10MHz carrier aka fundamental aka 1st harmonic is in its level is displayed ok. Second harmonic, 20Mhz is well inside specifications around -42.5dBc

We can not see more harmonics due to used very wide (300kHz) RBW so 3rd and higher harmonics are under displayed noise level.

Used "Mixer level", btw, is in this @noreply image -37dBm,  so  SA own generated harmonics are nearly around as low as it can be. SA specs are given for -30dBm 1st mixer "mixer level".  Att 50dB and signal level in input +13dBm so -37dBm.


It must say that Siglent signal generator is RF generator.
Rigol here is dds function generator. Even when they go also to same frequencies  they are very different.
ETA: OMG..  somehow I think there was R's function gen. Perhaps due to used low freq and also these R's model numbers... DG and DSG...  and yes @TT leas I did not  note N connector... also perhaps R's overall size was so small... so my apologize messing things..     It DSG800 IS of course RF generator. Period.

Not for this case... I have seen many times, also Siglent function generators give less harmonics levels than example high quality HP RF generator, I remember I have made some this kind of tests example with some HP8642B. These old tests can see somewhere deep inside this forum if I remember right and also in many data sheets.  Typically RF generators output power amplifier and after then attenuator and leveling stage is very different (with reason) than in typical function generators.
Take very narrow RBW and go to very close  carrier and down to bottom...



« Last Edit: July 24, 2020, 01:24:13 pm by rf-loop »
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Online TurboTom

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #11 on: July 23, 2020, 03:31:51 pm »
If I understand @noreply's tests correctly, he has done the measurements on both generators at the N connector, so there's no DDS or whatever function generator business going on in case of the Rigol instrument. Since the photo function of the forum is still broken, it's only superficially visible in the thumbnails which connectors had been used.

So it is obvious that Rigol's signal generator has a much lower second harmonic vs. Siglent's counterpart. My reverse engineering of this device also indicates that the output stage is designed for way more power output than it will ever "experience" in this generator, so it's possible that it's pretty linear at the powers it's used at (provided it's a class A design with sufficiently high quiescent current).

Another detail that may be quite interesting are the "dimples" in the spectrum at 5MHz intervals in the test of Rigol's generator. I'ld love to see the same spectrum taken at a much lower resolution bandwidth (in order to lower the noise floor) and maybe some trace averaging. Is there really a "forest" of peaks somewhere at -50dBc? If there is, it may be interesting to check the higher bands, i.e. at a frequency that isn't generated by mixing (> 227.5MHz). Siglent's generator doesn't appear to show these artifacts.
 

Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #12 on: July 23, 2020, 05:03:25 pm »

Another detail that may be quite interesting are the "dimples" in the spectrum at 5MHz intervals in the test of Rigol's generator. I'ld love to see the same spectrum taken at a much lower resolution bandwidth (in order to lower the noise floor) and maybe some trace averaging. Is there really a "forest" of peaks somewhere at -50dBc? If there is, it may be interesting to check the higher bands, i.e. at a frequency that isn't generated by mixing (> 227.5MHz). Siglent's generator doesn't appear to show these artifacts.

@TurboTom

I'm waiting to get some feedback from toutech on his analysis settings - as questioned in my post?

If I do , I will repeat my test with the EXACT settings he used.

After reading rf-loop's input as well as your comments - I will do some specific 'low noise floor' narrow RBW to see any harmonic artifacts on the Rigol.

My guess is that there will be quite a few - but Rigol did a good job at suppressing them low enough that it makes no difference to the user - since its well below the published specifications.

rf-loop could be correct - the Siglent may have fewer harmonics - but hey must have had some difficulty in trying to suppress them below a significant 'specification' level.

I will run this again on the Rigol & Siglent - but with different SVA settings that toutech used - so we can get more details at the lower levels.

rf-loop implied that the DSG800 series is not a true RF generator (digitally synthesized) - this as you said goes against your findings and I am not qualified to this level where my input would have any bearings.

BUT

I am happy to make any test you suggest to verify (via analysis) and possibly give you and rf-loop some insights to determine the most likely operation and architecture of the DSG800 series.

Looking forward to your input.

Take Care

 

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #13 on: July 24, 2020, 01:36:48 am »
When unexplained measurement levels are made, due to the many and deep menus it is best to press Preset to return SSA/SVA to know settings and try again.
Previously SSG and SVA clocks were linked using the SSG 10 MHz OUT for frequencies to be aligned.

Not so for the following screenshot where both instruments are running independent of any reference.
This time @ 1 GHz 0dB and again looking for harmonics of which the first is again ~50dB down like it was for 10 MHz @ 10dB.
For such a wide sweep when it is already ~3ks/sweep further reduction of the BW to lower noise floor would only delay what is already an acceptable result.

Improved SSG3021X  ;)
« Last Edit: July 24, 2020, 01:45:39 am by tautech »
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Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #14 on: July 24, 2020, 12:11:22 pm »
Thank you for your input tautech

I’m sure everyone appreciates the opportunity to ‘see’ more response plots – however rather than make measurements to verify if the Siglent SSG is indeed performing within its published specifications (as you pointed out) was not the objective of this thread.

What best serves the members of this forum and any other ‘viewers’ who have not registered – it to understand the behaviour and performance or EACH of the respective manufacturers products – namely their - RF signal generator offerings.

Weather Rigol or Siglent meets their publicized specification is not under investigation here.

What’s nice to see – from testing these devices – side-by-side – are any ‘clues’ in how the signals are generated, any benefits one approach might have against the other, and more importantly – identify any limitations or other design aspects which could be taken advantage during day-to-day use of the instrument.

So, I hope you understand, that simply taking measurements – without any direct ‘reference’ to the other product under test – serves little purpose in the scope of this thread.

Oh, just for the record, when testing ‘specifications’ – to see if Siglent or Rigol is indeed performing within their published harmonic levels, it is BEST to use the HIGHEST ‘in calibration’ output level of the device – which happens to be identical at +13dBm for BOTH of the instruments.

Performing a harmonics test at 0dBm – although useful data – is not a true indication that the instrument will have a similar performance at +13dBm and be within its published specifications at this output level as well – if that was the objective of the test.



OK, with the above out of the way, I can now report some interesting findings – at least for turbotom and rf-loop,  who might be able to interpret these with relation to the respective devices architecture and inherent performance differences.


One notable screen capture which I would like to comment on is the – image 1 – “rigol 13dbm 200mhz harmonics.png


Looking at this – we can see the significant ‘roll-off’ in noise floor after the fundamental frequency.

I don’t know what’s going on here – but if this is ‘by design’ – it’s pretty clever – because they just dropped the noise floor (and subsequent harmonics) by about 8dBm – VERY CLEVER.


I did EXACTLY same plot with Siglent SSG by just switching the respective outputs of the RF signal generators – this time to the SSG’s output N connector.

Please see – image 2 – “siglent 13dbm 200mhz  harmonics.png

You will note that the general response looks similar – but has a higher noise floor – almost exact same level – approx. 8dBm (visual observation from plot – unfortunately I did not measure at the time) that was somehow ‘reduced’ on the Rigol.


From this observation alone – it can be seen that Rigol is definitely doing something “in addition” to reduce the harmonic noise floor – and succeeded – otherwise the response(s) look very similar.


@turbotom, @rf-loop

If this is the ‘smoking gun’ that you and possibly rf-loop were looking to find – perhaps both of you can discuss?


I have made some additional plots and posting below – these are ALL at +13dBm – to stress the harmonic response – at various frequencies , and more importantly SVA’s frequency span.

I found that marker measurements can vary – depending on the frequency span under analysis – so was mindful of this by taking a range of readings and screen captures.


Hope this data is useful – looking forward to your comments / analysis.
 

Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #15 on: July 24, 2020, 12:17:26 pm »
After making above post - the 'already posted' images of previous posts got messed up

This IS A KNOWN PROBLEM - in the forum and Dave or moderators have not rectified.

Any present / past and future readers of this thread - please be aware of the above!

I don't know if this will be 'fixed' and when it is - weather the images will get corrected automatically  :-\
 

Offline rf-loop

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #16 on: July 24, 2020, 01:52:33 pm »

One notable screen capture which I would like to comment on is the – image 1 – “rigol 13dbm 200mhz harmonics.png


Looking at this – we can see the significant ‘roll-off’ in noise floor after the fundamental frequency.

I don’t know what’s going on here – but if this is ‘by design’ – it’s pretty clever – because they just dropped the noise floor (and subsequent harmonics) by about 8dBm – VERY CLEVER.


I did EXACTLY same plot with Siglent SSG by just switching the respective outputs of the RF signal generators – this time to the SSG’s output N connector.

Please see – image 2 – “siglent 13dbm 200mhz  harmonics.png

You will note that the general response looks similar – but has a higher noise floor – almost exact same level – approx. 8dBm (visual observation from plot – unfortunately I did not measure at the time) that was somehow ‘reduced’ on the Rigol.



Due to this forum image attachment total mess (how long it take to repair)
I need ask if these are now right

I do not know if yoyr words there is some kind of sarcasm or what ever but  In my eyes it looks that Rigol  rise noise level near carrier this 8dB and  more far from carrier it drops to "normal" like it is all time in Siglent. So what is rising around carrier noise level in Rigol so weird looking shape.  But is it so that these images are ok and not swapped or what ever mess...

This is why I ask dive more deep inside near carrier bottom corner. You have there more narrow RBW for use when look near carrier USB or LSB bottom corner. So it can perhaps show what is there or if it is some kind of bit weird PN.


named as Rigol


named as Siglent


Can you take both these carriers alone with lot of more narrow RBW so we can see what is there. This 1st image near carrier bottom looks extremely weird. So it is nice if you can dive more deep inside this..

But then need also give some note. Your signal level is around +13dBm and SSA attenuator is 20dB !!
And you are looking harmonics. Which one you want look, SA's os DUT's.

You run SA with -7dBm Mixer level!  For analyze DUT's harmonics it is lot of too high level! Even when this is same for both signal generators but with this setup there can easy drop to trap. Because... I think no need explain..  So least it need cross check with other settings so that what ever it makes to noise floor but look how much different settings affect carrier and harmonics ratio.
« Last Edit: July 24, 2020, 02:44:16 pm by rf-loop »
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Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #17 on: July 24, 2020, 02:31:06 pm »
Thank you for your insight rf-loop

I will get a 'zoom-in' for the area of interest.

Yes, you are right - near carrier the noise level is higher

I used an inappropriate reference to noise floor - whereas what I meant to signify is that the resultant harmonic levels dropped by this same amount.

My thinking (not necessarily correct at all) - was that the Rigol design - somehow 'dropped' the noise floor - because its the harmonics  are certainly lower at higher frequencies.

Anyway I will run some analysis & post results ASAP

« Last Edit: July 24, 2020, 02:38:21 pm by noreply »
 

Online mawyatt

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #18 on: July 24, 2020, 03:03:33 pm »
It's likely the close to carrier noise of the Rigol is due to some waveform type dithering.

Best,
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Re: Siglent SSG3021X - testing feedback and comments
« Reply #19 on: July 24, 2020, 03:49:21 pm »
@rf-loop

Here are a few new 'zoomed-in' plots

I had to offset the scales - so could 'fit' the area of interest - so please take the offset dBm into account when looking at the marker readings.

I then did a 'difference' on two randomly placed markers (6 and 7) - just so we can get the value of the 'drop' of the floor just after the fundamental frequency.

I started the plot at 10Mhz and went just after the 1st harmonic

Did another plot from 5Mhz to just after the fundamental of 200MHz

If you need any further testing of specific areas OR be 'zoomed' - just ask.

Hope this is useful  :)

« Last Edit: July 24, 2020, 03:51:19 pm by noreply »
 

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #20 on: July 24, 2020, 04:02:38 pm »
As @rf-loop already pointed out, the raised noise floor of Rigol's machine between DC and approx. 300MHz is peculiar. I relate this to Rigol's approach to generate the frequency band of 9kHz to 227.5MHz by mixing the 910MHz of the reference with the LO frequency range of 682.5~901MHz. This mixer is followed by an amplifier and a low pass filter, all of these located on the "wrong" side of the PCB. It may well be possible that these components pick up / generate some noise and the low pass filter limits it right to the range that can be observed. The following test may be useful to understand the situation: keep the SA setting as in the initial test and increase DSG frequency step-by-step above 227.5MHz so the DSG switches ranges. If in this moment, the noise band vanishes, it's related to the band1 mixer/amplifier/filter circuitry.

One more peculiar thing I observed: Peak no. 7 @ 138.2MHz with approx. -56dBm is more or less identically present in both the spectra -- which makes me assume that this is some noise picked up by the setup elsewhere and not generated by the signal generators. You may want to test the "output signal" of the generators while powered down to verify this.
« Last Edit: July 25, 2020, 07:45:13 am by TurboTom »
 

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #21 on: July 24, 2020, 07:14:04 pm »
@turbotom

I did some more plots as you suggested - thank you.

Looks like you 'hunch' panned out  :-+

The plot - see image below - tries to show the following;-

I recreated 'zoom-in' area of interest - and switched on  some markers for reference - remember to take into account the large offset.

I then tried to make multiple traces - so we can easily see any differences.

Unfortunately on the SVA there are only 4 traces - also I discovered a bug - the text color will not match the trace color when you save the plot INVERTED file - so be aware of this.

So to avoid confusion with trace labels and mismatch in colors - I used a non inverted (black background) plot which is attached.

I checked the DSG - before starting traces - and did a full spectrum 'zoomed' sweep - there is NOTHING coming out of the DSG in its stand-by mode - in essence when the RF out is OFF - its OFF!

I then used same output level for ALL traces +13dBm - highest 'in calibration' setting for the Rigol (same as Siglent) and started traces at 200MHz

Second trace was at 210, third at 220, then I did two traces - not captured - just for me to check in fine detail - 227 - (was same as 220 - the DSG obviously did not switch ranges) , then at 228 - BINGO - DSG switched ranges!

I then did a captured trace at 230

So all the traces can be seen on ONE plot

200MHz, 210MHz, 220MHz and the 230MHz - where the DSG obviously switched at 227.5MHz as you suggested  :popcorn:

OK, now that's this is clarified - despite the noise floor being similar to Siglent SSG - Rigol still has significantly lower Harmonic response - any comments / explanations for this observation - with relation to architecture / circuit design?

Thanks
 

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #22 on: July 24, 2020, 08:10:50 pm »
A screenshot saved from a previous check of SSG3021X PN @ 10 MHz 10dB at Span's of 2 MHz and 2 KHz:

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Offline rf-loop

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #23 on: July 25, 2020, 01:57:26 am »
@rf-loop

Here are a few new 'zoomed-in' plots

I had to offset the scales - so could 'fit' the area of interest - so please take the offset dBm into account when looking at the marker readings.

I then did a 'difference' on two randomly placed markers (6 and 7) - just so we can get the value of the 'drop' of the floor just after the fundamental frequency.

I started the plot at 10Mhz and went just after the 1st harmonic

Did another plot from 5Mhz to just after the fundamental of 200MHz

If you need any further testing of specific areas OR be 'zoomed' - just ask.

Hope this is useful  :)

1st question. I hope more words do not affect for more mess.

Image names tell 13dBm signal level. Is it true. Is it SA input level or externally attenuated generator output level.
If it is SA input level +13dBm it is far too high. Perhaps not make so much bad in this case but we can not be sure. So please use -30dBm mixer level to be sure SA works inside specs with its own generated harmonics etc products in first mixer.

Then please drop Generator level to example to -70dBm (200MHz carrier) and turn AM modulation ON, use 50Hz modulation and modulation depth 0.1% - if can not more low.   Set SA  Attenuator to 0dB and Span 1kHz or less and RBW 1Hz. As I told earlier I like to see near carrier and its bottom corner. It depends now lot of how this Rigol's extra noise  widely around carrier goes and what it is.

Then look also how this wideband noise floor around 200MHz drops and how also these non harmonics spurs drop if they drop when signal is more low and you can also go more down with SA what have also its own phase noise what is next thing where you hit your head very easy when you are near carrier where it is more low than example 10kHz away from carrier what is not anymore near carrier.

Harmonics are not RF generators achilles heel. non harmonic spurs are and phase noise, residual FM etc things are.
Of course these are not at all high class RF generators, as can also see in specs and there is harmonics levels are not main thing at all. Look example some "state of art" RF generators +35dBc harmonics specifications and  think why. Yes they can suppress these but why because they, pure harmonics,  are not key factors in state of art RF generators.
« Last Edit: July 25, 2020, 04:17:29 am by rf-loop »
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Offline noreplyTopic starter

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Re: Siglent SSG3021X - testing feedback and comments
« Reply #24 on: July 25, 2020, 08:05:38 pm »
@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
« Last Edit: July 25, 2020, 10:44:34 pm by noreply »
 
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