SSA3021x Spur 345 MHz - Page 1
Forum section: electronics / testgear

author: AlphaBob
author_rank: Newbie
timestamp: December 13, 2016, 07:29:53 pm
content: Hi,I received a Siglent SSA3021x Spectrum Analyzer about a week ago and its performance has blown me away. In doing some emission tests, I discovered a rather strong spurious emission that appears to be coming from inside the analyzer itself, as it doesn't go away with a terminated input, nor does it seem to be AC power or position dependent. The Tracking Generator is turned off.The 345.0 MHz spur is -72.6 dBm and appears to have some mild sidebands that extend +/- 5 KHz around -92 dBm.above and below that are about -92 dBm. JPG attachedThe unit was received directly from Siglent NA in Ohio and was calibrated in late November 2016. Firmware is same version 7.07 that Siglent is providing for download on their website.Has anyone else noticed something similar?

author: tautech
author_rank: Super Contributor
timestamp: December 13, 2016, 08:12:21 pm
content: Welcome to the forum.Can't say I noticed it but I'll put a link to your thread on the SSA3kX thread for better visibility.https://www.eevblog.com/forum/testgear/siglent-ssa3000x-spectrum-analyzers/Can you post your FW version please.

author: TurboTom
author_rank: Super Contributor
timestamp: December 13, 2016, 08:46:02 pm
content: Yes that spur is definitely there. It's not coupling via the input since it always appears to be approx. 20dB above the noise floor (on my machine @ 300Hz RBW -- and around 33dB @ 10Hz RBW), regardless of attenuator setting or wether the preamplifier is enabled or not. So it may be an internal signal that's directly coupling into one of the IF circuits.There has been a discussion about these spurs some time ago (there are many more) and the conclusion was that no SA in the world will be completely free of them.Cheers,Thomas

author: AlphaBob
author_rank: Newbie
timestamp: December 13, 2016, 08:50:50 pm
content: Quote from: TurboTom on December 13, 2016, 08:46:02 pmThanks Thomas -- I can understand that point of view, but feel even better knowing that it isn't just my SA.

author: KE5FX
author_rank: Super Contributor
timestamp: December 13, 2016, 09:03:51 pm
content: Quote from: TurboTom on December 13, 2016, 08:46:02 pmSounds like an exercise in lowered expectations. The price that Siglent charges for that dubious display of performance would buy you a 35-year-old HP 8568A that has no such issues.Of course, in its day, that HP cost about as much as a new Ferrari. It still consumes more than its share of electricity and gravity, and you will probably need to open it up and fix it at some point, assuming it even survives the tender ministrations of UPS on the way to your house.Meanwhile the Siglent is the size of a lunchbox, weighs even less, and can be purchased brand new with factory warranty for the price of a nice lawnmower. They get points for that in my book... but make no mistake, there's no good excuse for the behavior in that screenshot.

author: Bicurico
author_rank: Super Contributor
timestamp: December 13, 2016, 09:04:38 pm
content: Hi,That is normal.Here is mine for comparison.Regards,Vitor

author: TurboTom
author_rank: Super Contributor
timestamp: December 13, 2016, 09:06:28 pm
content: Of course -- I would feel the same if I had this machine just new. You can quite easily distinguish between internal spurs that aren't coupled into the SA via the input and "real" input-related signals by changing the attenuator setting. The relative signal amplitude of the spurs over the noise foor will stay unchanged while the signal will vanish in the noise if the attenuation is increased, or to put it the other way round, the absolute (displayed) input signal will stay constant while the absolute strength of the spurs will change with attenuation setting.Cheers,Thomas

author: rf-loop
author_rank: Super Contributor
timestamp: December 13, 2016, 09:19:45 pm
content: Previously:https://www.eevblog.com/forum/testgear/siglent-ssa3000x-spectrum-analyzers/msg981095/#msg981095Quote from: rf-loop on July 11, 2016, 06:45:02 amIf look example Keysight N9320B .... well, it reads in specifications and Siglent do not need shame anything.Of course I and perhaps everyone like if there is less and spurs are more low. But, it is this. And it is not alone in this spur club.

author: KE5FX
author_rank: Super Contributor
timestamp: December 13, 2016, 10:28:33 pm
content: Quote from: rf-loop on December 13, 2016, 09:19:45 pmThere are specs, and then there's typical real-world performance.If you're building a spectrum analyzer, you obviously want to be careful about what you promise. If I'm wearing the designer's hat, I might specify -80 dBFS SFDR to allow for real-world customer use cases with marginal test environments and practices, but if Ipersonallysee a spur anywhere near that level while I'm using my own gear, no further work is going to be done that day (or that week) until I understand where it's coming from. I certainly won't ship the product until it's understood and resolved. And if a paying customer was the first to notice something like the spur we're talking about here, I'd look for a nearby bridge to jump off of.It is not the case that it's "impossible" to build a spur-free spectrum analyzer. Fire up the aforementioned HP 8568B and find an internally-generated, non-line related spur that's anywhere near the specified limit. Go ahead, I'll wait.Unless there's something wrong with the analyzer, you won't succeed. That's because HP did something that Siglent evidently didn't bother to do: their firmware anticipates where spurs will appear, and adjusts internal oscillators during the sweep to avoid them. I don't know if HP patented that idea, but if they did, it expired 20 years ago... so once again, there's no excuse beyond the desire to save a few bucks.I don't know anything about the N9320B, but I will say that I've been really impressed by the quality and performance of the N9340B portable. Dave's teardown video of that one was just amazing; it pretty muchisa portable 8568.

author: AlphaBob
author_rank: Newbie
timestamp: December 13, 2016, 11:02:48 pm
content: Quote from: KE5FX on December 13, 2016, 10:28:33 pmNow that is clever and Siglent should be able to accomplish something similar in their firmware, if they care to.

author: Dubbie
author_rank: Unknown
timestamp: December 14, 2016, 02:41:35 am
content: Here is my 345Mhz spur.

author: rf-loop
author_rank: Super Contributor
timestamp: December 14, 2016, 05:09:51 am
content: Quote from: KE5FX on December 13, 2016, 10:28:33 pm... yes I can see.I have owned several HP spectrum analyzers previously, and long time. Short time ago last one, 8568B, I throw away. Some tiny function generator tests made with it (using your software) can also find here in forum. Also previously least as good as HP (or bit better) and more heavy R&S.. There is enough difficult to find internal non input related spurs. This kind of spectrum analyzers what are in Rigol 800 and Siglent 3000 class are not at all comparable to these nearly State Of Art class old machines. They are not comparable with weight and not with SA performance.Siglent have never not even tried or designed to make High End or State Of Art level SA's. There is no any reason to go this market sector.We need cheap oscilloscopes and cheap spectrum analyzers for every asian student and engineer table in new world. For understand basic things and make basic measurements with scopes and SA's do not really need state of art class equipments. Where one really NEED High End equipments really, these are worldwide available easy with money.Moreover, the lack of skills can not be replaced by owning expensive High End equipment. Except when absolutely prominent position on the most expensive and the best camera alongside the street, and hopes that all would see.Travel to nearest CRH station can do using cheap electric scooter or bicycle or tiny Micra or it can do with black RR. There is needs for all.

author: DL4RAJ
author_rank: Contributor
timestamp: December 17, 2016, 06:56:26 pm
content: Quote from: rf-loop on December 13, 2016, 09:19:45 pmIt seems that during production considerable improvements in hardware design have been done without notice.I have duplicated your settings exactly and made two screenshots for comparison.The spurs are much weaker on my analyser.My SSA was purchased around 24th October 2016.S/N HA3160481SW1 1.2.8.1SW2 20160622-2SW3 000000D1HW 07.03.00regards

author: tautech
author_rank: Super Contributor
timestamp: December 17, 2016, 07:25:10 pm
content: Quote from: DL4RAJ on December 17, 2016, 06:56:26 pmThanks.Could you list your HW and FW versions please ?Maybe built date too, xxxxxxx316xxxx is what it might look like in the SN#EditFor the sake of neatness, maybe add it to your above post as an edit.

author: DL4RAJ
author_rank: Contributor
timestamp: December 17, 2016, 09:05:28 pm
content: Quote from: tautech on December 17, 2016, 07:25:10 pmDone.

author: rf-loop
author_rank: Super Contributor
timestamp: December 18, 2016, 10:15:13 am
content: Quote from: DL4RAJ on December 17, 2016, 06:56:26 pmI have exactly same version as you. Difference only in serial number.S/N SSA3XHA216xxxx (as we know after last digits 6000 (or was it 6100) there was TG hardware some improvements)SW1 1.2.8.1SW2 20160622-2SW3 000000D1HW 07.03.00As can see some spurs in your equipment are more low and some more high.But then over whole frequency span your equipment base noise is higher.I have tested more than just one SSA and I can say there are some differences between individual units, as is particularly natural.This is why every spectrum also have individual calibration tables (and it is example for every 51 attenuator positions and over whole frequency span) Base noise level is "where ever" after cal factors and as long as base noise level meets equipment specifications, it is ok.Every amplifier, every mixer, every filter, every attenuator - everything have own variations between some tolerances. Finally after summing all together result is "random" but inside some rough limits. It is even possible that some small fraction from manufacture lot do not meet specifications at all but perhaps meet other model specs. All peoples whoi have been in any electronic equipments manufactuuring know this.But as we know. There is also interesting model table. SSA3010X, SSA3015X, SSA3018X, SSA3021X, SSA3030X, SSA3032X... it is well possible that if example some unit do not meet all SSA3032X specs it can still be ok for SDS3010. (just same as example some oscillosscopes analog front ends etc)Sidenote (not big difference in result)You told you have used same settings. No you have not. Look your image about 1540MHz. There read FFT ! In my image, there do not read FFT. Of course if user keep "All Auto" mode spectrum set as default FFT if it can. But it is also good to know that sometimes sweep mode is good even when it is much more slow.

author: DL4RAJ
author_rank: Contributor
timestamp: December 18, 2016, 11:53:27 am
content: Quote from: rf-loop on December 18, 2016, 10:15:13 amHere is the same screenshot without FFT.Spurs are now about 2dB stronger than in my last screenshot with FFT but still 10dB weaker than in in your screenshot.regards

author: bozidarms
author_rank: Regular Contributor
timestamp: December 18, 2016, 01:03:22 pm
content: Hi to the group,Here is the same screenshot from my SSA:S/N SSA3XHA3160xxxSW1 1.2.8.1SW2 20160622-2SW3 000000D1HW 07.03.00Seems that mine have a little bit lower noise, more regular shape, and almost no 345 MHz spur (but have others).Both traces without any averaging.

author: pascal_sweden
author_rank: Super Contributor
timestamp: December 18, 2016, 03:17:15 pm
content: Why doesn't Siglent implement some kind of calibration feature in software, where the user has to ensure that there is no input signal connected to the front-end, and the spectrum analyzer would sweep the full spectrum and equalize out the internal spurs?In the current implementation, you would almost have to order 4 units at the same time, try out all of them, keep the best unit, and send back the other 3 units within the available return time of the distributor

author: rf-loop
author_rank: Super Contributor
timestamp: December 18, 2016, 06:15:29 pm
content: Quote from: pascal_sweden on December 18, 2016, 03:17:15 pmThis same can do with Keysight, Tektronix, Rohde&Scwartz, Anrizu, Advantest, SignalHound, GoodWill, Rigol .... and so on.For @pascal_sweden......, all can do. Are you now happy? 1540 and 1904MHz spurs are nearly gone...Attached image is untouched original png from "tweaked" SSA.Input teminated, full span, RBW=VBW=1kHz. Atten 0. Detector Pos Peak.When I did this tweak I use chinese bamboo (material is important) chopsticks and glass tea cup (it need be glaass, not porcelain) and dry genuine rice paper (mandatory). No need solder anything and no need hammer or screw driver.

author: DL4RAJ
author_rank: Contributor
timestamp: January 02, 2017, 01:28:40 pm
content: Quote from: rf-loop on December 18, 2016, 06:15:29 pmI've used German Bratwurst and Sauerkraut for my tweak. _.)Seems to work even a bit better.

author: rf-loop
author_rank: Super Contributor
timestamp: January 03, 2017, 12:03:44 pm
content: Quote from: DL4RAJ on January 02, 2017, 01:28:40 pmOf course this more advanced method "I've used German Bratwurst..." helps lot of...