EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: TomC on May 04, 2023, 10:49:43 pm
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These went on sale a few months ago at Walmart's marketplace from several Chinese vendors. I've been wanting a spectrum analyzer to play with for years, but couldn't afford the $2500 and up price just for my electronics hobby. So when I saw these I snatched a brand new one for under $600, delivered. Its been a couple months but I haven't had much time to play with it, and truthfully, I'm very new to this devices since I've never owned one before. If any one is familiar with these any comments will be appreciated! I may post more of my experiences with this new toy in the future if there is any interest.
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Hi, I don't have this device, only a similar one from the competition. I want to give you a piece of advice, namely to start by purchasing a set of attenuators at least 10db and 6db, but 3db and 1db would also be good. You always have to have an external attenuator when testing something new or something you don't know everything about. Similarly, after any modification in the DUT, you must start with an external attenuator of 10db or 6db. Any connection or disconnection from the power supply or a sudden abnormal regime can exceed the strength of the signal entering the analyzer. You have to be very careful with the first mixer, even if it has some protection that displays a warning message on some analyzers.
After everything is under control, you can remove the external attenuator and continue the measurements.
An old military technician told me that whoever has an analyzer and his first mixer didn't burn means that either he didn't work enough or he was very lucky. From my not very big experience, I say that he is right. I recommend attenuators from Minicircuits FW-10+ and so on which are at 1W and 12gHz. And one more thing, do not connect the input of the analyzer to the DUT until the latter is not in a stable regime. :)
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Hi nenea dani
Thanks for the hint! I did read about the mishaps with mixers and bought a 20dB 25 W at the same time I got the analyzer. I also have an old variable that has 1, 3, 6, 10, 10, 20, 20 dB switches.
Currently I'm comparing the specs of the Owon XSA1032-TG that I have with what appears to be a similar unit from Rigol, the DSA832E-TG. It's taking longer than I expected because they use different names for the same spec in some cases.
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An old military technician told me that whoever has an analyzer and his first mixer didn't burn means that either he didn't work enough or he was very lucky.
Don't tell my manager that - I've been using lab and portable spectrum analyzers for over 15 years and have yet to damage one (knock on wood) :)
Our service center does occasionally get spec ans where someone has burned out the front end by connecting to something they shouldn't have, but it's not as common as one might think.
But you're absolutely right, it doesn't hurt to connect an attenuator if you're not sure what you're looking at. I sometimes even start with the bigger one :)
https://www.instagram.com/p/Cq-SNEIuUhc/ (https://www.instagram.com/p/Cq-SNEIuUhc/)
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I worked for a while with a Systron Donner 809-1 which is a heavy tank in the field and I never protect it. However, with a small amplifier I managed to fry his first mixer. It took 30 seconds to change the mixer diode, but in some analyzers the mixer is molded together with many other parts. All evil leads to good because I later managed to build a cartridge type mixer with Schottky diode. What can I say, each with his own stories. :)
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An old military technician told me that whoever has an analyzer and his first mixer didn't burn means that either he didn't work enough or he was very lucky.
Don't tell my manager that - I've been using lab and portable spectrum analyzers for over 15 years and have yet to damage one (knock on wood) :)
Our service center does occasionally get spec ans where someone has burned out the front end by connecting to something they shouldn't have, but it's not as common as one might think.
But you're absolutely right, it doesn't hurt to connect an attenuator if you're not sure what you're looking at. I sometimes even start with the bigger one :)
https://www.instagram.com/p/Cq-SNEIuUhc/ (https://www.instagram.com/p/Cq-SNEIuUhc/)
I don't have a spectrum analyser or ever interacted with a bench one. I'm curious about the mechanical aspect of connecting that chonky boi to the analyser's input, do you need to use a cable between the analyser and the attenuator? o.o or are the connectors sturdy enough to just plug it in and not make you worry about mechanical damage?
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I don't have a spectrum analyser or ever interacted with a bench one. I'm curious about the mechanical aspect of connecting that chonky boi to the analyser's input, do you need to use a cable between the analyser and the attenuator? o.o or are the connectors sturdy enough to just plug it in and not make you worry about mechanical damage?
Oh, definitely a cable - that attenuator is even heavier and bulkier than it looks in the picture.
I never hang any weight (other than a few centimeters of a standard cable) off a spectrum analyzer input, even sometime as light as a typical noise source. Most of the labs I've been in have small lift stands like this one for holding things like power sensors, DUTs, filters, preamps, etc. Trust me, it's worth the money. You can also just prop things up ad hoc with a few books, etc. in a pinch.
But yeah, always a cable when I'm using the big one :)
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I don't have a spectrum analyser or ever interacted with a bench one. I'm curious about the mechanical aspect of connecting that chonky boi to the analyser's input, do you need to use a cable between the analyser and the attenuator? o.o or are the connectors sturdy enough to just plug it in and not make you worry about mechanical damage?
Oh, definitely a cable - that attenuator is even heavier and bulkier than it looks in the picture.
I never hang any weight (other than a few centimeters of a standard cable) off a spectrum analyzer input, even sometime as light as a typical noise source. Most of the labs I've been in have small lift stands like this one for holding things like power sensors, DUTs, filters, preamps, etc. Trust me, it's worth the money. You can also just prop things up ad hoc with a few books, etc. in a pinch.
But yeah, always a cable when I'm using the big one :)
ooh, cool, thanks, that makes sense. I really like the tiny lift! :-/O
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XSA1032-TG vs DSA832E Specifications.
I finally finished compiling the published specifications for these two units and creating a document where they can be compared side by side. They still look similar to me. The Rigol has better numbers in a few important areas, but the OWON has a few features that are either optional or not available for the Rigol. So all in all, I still think that for the price I paid for the OWON, if it actually performs as indicated in the specs, I did pretty good!
To get some hands on with the new toy, and to try to verify some of the specs, I'm going to try to test some of the specs with the equipment that I have available. Currently I'm working on the "SSB Phase Noise" specification. So as soon as I'm finished I'll post the results including the pertinent screen images from the analyzer.
@pdenisowski
I also like the little lift, I saw a very similar one at Amazon for $16, so I ordered it. Thanks for the tip :)
Note: I've recently discovered some errors in the attachment, particularly the 2nd Harmonic Distortion section. I'm working to try and get that corrected and will replace the attachment soon :palm:.
Attached corrected specs as of 5/17/2023
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SSB Phase Noise Test part 1
To perform this test I need a signal generator that can output a 1GHz signal, and has better Phase Noise specs than the Spectrum Analyzer. The only signal generator capable of 1GHz that I have available is my SynthUSBII that can output from 34MHz to 4.4GHz. The manufacturer didn't provide specs for the assembled unit, but since it is based on the ADF4351, I'm looking at the noise specs for that IC and they seem to fit the bill. They are using 2.2GHz instead of 1GHz for the noise test, but I'm going to assume that that's good enough.
The signal generator is only 1" x 2", so I have it directly connected to the Spectrum Analyzer's RF input. Attachments 1 - 4 show the pertinent ADF4351 specs, the SynthUSBII settings, and the spectrum of the generator's output at full Span. These signal generators don't have a calibrated output, but as can be seen it comes pretty close to 0dBm with the settings at max power. The prominent third harmonic is due to the ADF4351 based generators design, their output is a square wave, but I don't think that will affect the test results, since the called for offsets are at 10kHz, 100kHz, and 1MHz.
I'll post the actual spectrums of the test next.
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SSB Phase Noise Test part 2
To setup and execute the test I used the following procedure:
1. Turn on the analyzer and allow it to warmup for at least 30 minutes.
2. Connect the generator to the RF input and set it up to 1GHz Max Pwr.
3. Use the analyzer's Auto-Tune to get a basic display.
4. Change the Detector to Sample, the Display to Ampt Graticule On, the Span to 25kHz, RBW to 1kHz, and turn Average On.
5. Set Marker to Delta 10kHz to place the marker at the 10kHz offset, set Marker Fctn to Marker Noise On to normalize the noise reading to 1Hz.
The Spec calls for "10 kHz < -82 dBc/Hz (Typical)" and as shown by the Step_5_Spectrum attachment we got a -83.15 dB/Hz noise reading. Since in this case the carrier power is pretty close to 0dBm, then I think -83dB/Hz is equivalent to -83dBc/Hz. In fact, since the carrier is actually slightly above 0dBm, it's probably closer to -84dBc/Hz.
The procedure for the 100kHz, and 1MHz offsets is basically the same except for the Span and Delta Marker, which need to be set to larger values. For the attached spectrums I used Span = 250kHz, 2.5MHz, and Delta = 100kHz, 1MHz.
As can be seen, the 10kHz, and 100kHz offsets appear to be within specs. However, the 1MHz offset is slightly off, but in my opinion, not by much.
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That's quite a sale - if you'r are able to pick them up at 600 bucks..like 1/4 of Wallmarts msrp. congrats..
cheers, from one envious puppy here ;D
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To tell you the truth, when I first saw it, I thought it was some kind of scam. But since Walmart generally stands behind anything bought from their website, I decided to take my chances and order it right away anyway, I didn't even research it. Although, since I own other OWON products (2 DSOs and 2 ARBs), I remembered seeing it on their website while looking for updates.
First I ordered from the vendor with the lowest price, about $425, but that fell thru with the package lost in transit, it never made it out of China. I got my money back and the price had gone up a little, so I ordered again for less than $600 and got my prize this time.
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Displayed Average Noise Level (DANL) Test part 1
To setup and execute the test I used the following procedure:
1. Turn on the analyzer and allow it to warmup for at least 30 minutes.
2. Connect a 50Ω terminator to the RF input.
3. The steps that follow assume you are starting from the factory preset settings, press Preset if needed.
4. Change the Detector to Sample, the Display to Ampt Graticule On, turn Average On, set Ref Level to -70dBm, set Attenuation to 0dB, the Start Freq to 1MHz, the Stop Freq to 1GHz, and Press Peak (Max Search) to find the noisiest spot in this range.
5. To get better resolution press Mkr→CF, and change Span to 1MHz. Note that the noise reading is lower because RBW & VBW were automatically changed to 10kHz.
6. Set Marker Fctn to Marker Noise On to normalize the noise reading to 1Hz. This is the DANL for PA off: 1MHz to 1GHz, the spec calls for -140 dBm (Typical), <-130 dBm.
7. Turn the Preamplifier to On. This is the DANL for PA on: 1MHz to 1GHz, the spec calls for -160 dBm (Typical), <-150 dBm.
The procedure for the 1GHz to 3.2GHz ranges is basically the same except for the Start and Stop frequencies on step 4. The attachments for steps 4-7 are on the next post.
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Displayed Average Noise Level (DANL) Test part 2
Here are the attachments for steps 4-7 of the 1GHz to 3.2GHz range.
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How does it handle immediately after 9kHz? Did you see the signal generated by TG? Does it have sufficient amplitude and the correct shape in 9Khz -50Khz? How is the sensitivity in this range?
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I wonder if you are thinking audio work?
I attached some spectrums that include the range you are thinking about, but as you can see the noise floor is quite uneven in that region. Probably means response is going to be uneven too. All I had handy right now was the 50 ohm terminator, but I'll experiment with a low frequency generator later on, maybe one of my ARBs, and post some spectrums.
On the last attachment I had the Start Frequency set to 9kHz before I turned on the amplifier, but if you look at the labels you can see that it automatically jumped to 99.95kHz. There for a second I thought I had found a way to flatten the noise floor, but it looks like they limited the frequency range you can use with the amplifier turned on.
From the little bit I've been able to research so far, I think that I read that SAs that start in the kHz range are AC coupled, which probably wouldn't be too good for audio.
I did look at the TG output a while back, but don't remember all the details. On this SA you have to set Span to 0 to use it as a generator. From what I recall it's a sine wave, and I was looking at about 0dBm with one of my DSOs that goes to 200MHz. I'll hook that up again and post some DSO screens and some FFT screens later on.
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What you are likely seeing at these lower frequencies is the phase noise of the SA sweeping oscillator which has a 1/f^n characteristic. The better the oscillator 1/f PN the better noise floor in this low frequency region.
BTW great buy for the OP, ~$600 :-+
Best,
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I'm really looking to find a way to use a 9Khz analyzer in the audio field. My Siglent SSA3021X tool has a weak signal between 9Khz and 50Khz, and in addition it is not really sinusoidal. I would somehow go with the normalization function. Now I'm experimenting with lowering the frequency with the help of an H-mixer. I take the spectrum between 20Hz and 100Khz to 1Mhz, obviously only with a very clean external sine signal.
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The PicoScope 4262 might be worthwhile to look into.
Best,
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What you are likely seeing at these lower frequencies is the phase noise of the SA sweeping oscillator which has a 1/f^n characteristic. The better the oscillator 1/f PN the better noise floor in this low frequency region.
BTW great buy for the OP, ~$600 :-+
Best,
Thanks for the tip!
Looks like you nailed it! I see at least a 10dB difference by just changing the Sweep from Auto (about 29ms in this case) to Manual 500ms. So at least at the very beginning of the sweep that made a big difference. I set the reference level to -30 in this set of attachments for better accuracy. Thanks again! :)
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TG Output at Different Frequencies Part 1
Some of the XSA100 series SAs can use the TG output as an independent CW generator. However, the XSA1032-TG is not one of them. The soft menu selections for this feature are grayed out as can be seen on attachment 2. But as is the case with other TG SAs, it's still possible to set the Span to Zero, turn on the TG output, and use the FREQ soft menu to set the output frequency (see attachment 1). The output level can then be set via the Source soft menu (attachment 2). 0dBm is the highest level and what I'm using for all the screens I captured from my SDS8202 DSO.
Attachment 3 is a screen of one of my favorite dB calculator websites showing some conversions for 0dBm. The website is at:
https://www.analog.com/en/design-center/interactive-design-tools/dbconvert.html (https://www.analog.com/en/design-center/interactive-design-tools/dbconvert.html)
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TG Output at Different Frequencies Part 2
The bottom left of the OWON SDS8202 screens shows a few automatic measures, but the names may be confusing, Vk is what they use to identify the RMS measurement, and Vp is what they use to identify volts peak to peak (Vpp). One other thing that may be confusing is that on the FFT screens the scale is on dBV, which is not mentioned anyplace as far as I know. The SDS8202 is rated as a 200MHz DSO, but on attachment 14 I think the drop in signal strength is due to the DSO being at the limit of its bandwidth.
Note: I had to replace the attachments because they were hard to read.
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9kHz to 100kHz Spectrums and Frequency Response
For these tests I'm using an OWON AG1022F Arbitrary Waveform Generator (AWG or ARB). The relevant specs for the Sine output and Sweep function are attached. Attachment 3 shows the AWG setup to output a 25kHz Sine at 633mVpp, since I'm using 50Ω that's around 0dBm. There's just a short 20" cable between the AWG and the SA. Attachments 4-7 show a few spectrums for AWG outputs in this range, including the 25kHz shown in attachment 3. They look pretty clean to me, don't even see any notable harmonics, and the dB levels seem fine.
Attachment 8 shows the AWG's setup to output a Sweep from 9kHz to 100kHz. I set the sweep length to 220 seconds to try to capture the frequency response using the SA's Trace Max Hold function. The idea is to let the SA sweep several times before the AWG changes the frequency (SA's sweep is set to auto which in this case is 404ms). Attachment 9 shows the SA's screen halfway thru the process, and attachment 10 shows when the process is completed. The entire process takes about 4 minutes. I don't know if there is an easier way to do this! So any one with a better idea please chime in. :)
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Frequency Response Test
To perform this test, I need a signal generator with a range that at least covers 100kHz to 3.2GHz with a nearly flat response. Unfortunately, I don't have a generator that matches those requirements. My AG1022F has an adequate response, but maxes out at 25MHz. I also have the Windfreak SynthUSBII that has a 34MHz to 4.4GHz range but has an uncalibrated output and the response is around plus or minus 4dB. So, I tried to do the test in two sections, 100kHz to 25MHz, and 34MHz to 3.2GHz. The first section gave me what I think are fairly accurate results, but the second section is just showing the response of the generator, not the SA.
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Was this SA really $600? I've seen them listed for like $2,600.
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Was this SA really $600? I've seen them listed for like $2,600.
Yes, I couldn't believe it was legit when I saw the prices they were selling for at Walmart's marketplace. Several chinese vendors had them listed anywhere between $425 and about $2600. See reply #12 where I posted the receipt:
https://www.eevblog.com/forum/testgear/owon-xsa1032-tg-3-2g-spectrum-analyzer/msg4854467/#msg4854467 (https://www.eevblog.com/forum/testgear/owon-xsa1032-tg-3-2g-spectrum-analyzer/msg4854467/#msg4854467)
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I still see some places where they are selling this SA for less than MSRP, not quite as inexpensive as what I got a few months ago, but under $1000. Funny thing is that these examples at Amazon call it a handheld, in reality, it weights about 11 pounds (5kg). Maybe they made too many of them and let a batch go to non-traditional vendors dirt cheap. Who knows? :o
https://www.amazon.com/Oumefar-Precision-Generator-Resolution-regulations/dp/B08QJQX4BD/ref=sr_1_86?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-86&ufe=app_do%3Aamzn1.fos.5137e923-c7be-4142-979c-7c68b6c26f63 (https://www.amazon.com/Oumefar-Precision-Generator-Resolution-regulations/dp/B08QJQX4BD/ref=sr_1_86?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-86&ufe=app_do%3Aamzn1.fos.5137e923-c7be-4142-979c-7c68b6c26f63)
https://www.amazon.com/Portable-Tracking-Generator-Precision-regulations/dp/B08QJR3KFR/ref=sr_1_85?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-85 (https://www.amazon.com/Portable-Tracking-Generator-Precision-regulations/dp/B08QJR3KFR/ref=sr_1_85?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-85)
https://www.amazon.com/Portable-Generator-Resolution-Precision-regulations/dp/B093CZJ3ZH/ref=sr_1_84?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-84&th=1 (https://www.amazon.com/Portable-Generator-Resolution-Precision-regulations/dp/B093CZJ3ZH/ref=sr_1_84?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-84&th=1)
https://www.amazon.com/Portable-Tracking-Generator-Resolution-regulations/dp/B08QJQ54XW/ref=sr_1_83?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-83&th=1 (https://www.amazon.com/Portable-Tracking-Generator-Resolution-regulations/dp/B08QJQ54XW/ref=sr_1_83?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-83&th=1)
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These Amazon sellers linked above, dang
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Detailed Seller Information
Business Name: yibinxihongshishipinyouxiangongsi
Business Address:
gaoxianqingfuzhenjixiangxiang84hao
yibinshi
sichuansheng
645154
CN
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Detailed Seller Information
Business Name: putianchengxiangfutaishangmaoyouxianzerengongsi
Business Address:
chengxiangquxialinjiedaolihuadongdadao8hao
putianwandaguangchang11haolou2ti805shi
putianshi
fujiansheng
351199
CN
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Detailed Seller Information
Business Name: Hong yu guang zhou shang mao you xian gong si
Business Address:
Tian he qu hua guan lu 1934hao 905fang zi bian B07
Guang zhou shi
Guang dong sheng
510665
CN
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- but then again, if you're in the US, and using Jeff Jorgensen's big A-store, you are likely pretty covered for not being sc3wed over, ain't it like 20 or 25% Amazon takes when selling on their platform.
But it seems it's no dice, outside the US, as it won't even show the price, if your region aint in the US, you have to manually put in a US postal code, and no' I definitely don't put in 90210 hence some 90s series' like its the only US postalcode I remember from scratch.
but with OPs mentioned price at sub 600 in mind, it seems like a decent SA, not least because it's the 3.2GHz variant.
are the lesser XSA10XX models. upgradeable, or how does Owon role, or does the hardware differs.?.
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I believe there are differences in the hardware. At least, for other OWON devices I own, that I've opened to look inside, that's been the case. I get what you are saying, about the non-traditional vendors, If I hadn't had some guarantee that the major retailer would have my back, I wouldn't risk dealing with them. Not because they are necessarily dishonest, but without a track record it's impossible to be comfortably sure. :)
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I still see some places where they are selling this SA for less than MSRP, not quite as inexpensive as what I got a few months ago, but under $1000. Funny thing is that these examples at Amazon call it a handheld, in reality, it weights about 11 pounds (5kg). Maybe they made too many of them and let a batch go to non-traditional vendors dirt cheap. Who knows? :o
https://www.amazon.com/Oumefar-Precision-Generator-Resolution-regulations/dp/B08QJQX4BD/ref=sr_1_86?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-86&ufe=app_do%3Aamzn1.fos.5137e923-c7be-4142-979c-7c68b6c26f63 (https://www.amazon.com/Oumefar-Precision-Generator-Resolution-regulations/dp/B08QJQX4BD/ref=sr_1_86?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-86&ufe=app_do%3Aamzn1.fos.5137e923-c7be-4142-979c-7c68b6c26f63)
https://www.amazon.com/Portable-Tracking-Generator-Precision-regulations/dp/B08QJR3KFR/ref=sr_1_85?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-85 (https://www.amazon.com/Portable-Tracking-Generator-Precision-regulations/dp/B08QJR3KFR/ref=sr_1_85?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-85)
https://www.amazon.com/Portable-Generator-Resolution-Precision-regulations/dp/B093CZJ3ZH/ref=sr_1_84?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-84&th=1 (https://www.amazon.com/Portable-Generator-Resolution-Precision-regulations/dp/B093CZJ3ZH/ref=sr_1_84?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-84&th=1)
https://www.amazon.com/Portable-Tracking-Generator-Resolution-regulations/dp/B08QJQ54XW/ref=sr_1_83?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-83&th=1 (https://www.amazon.com/Portable-Tracking-Generator-Resolution-regulations/dp/B08QJQ54XW/ref=sr_1_83?crid=S55K50VOUZ7C&keywords=XSA1032&qid=1684086658&sprefix=xsa1032%2Caps%2C146&sr=8-83&th=1)
This entire thread looks to me like a SCAM!
Devices at Amazon in these links have the OWON brand grayed out from the label, take a close look!
In the initial post https://www.eevblog.com/forum/testgear/owon-xsa1032-tg-3-2g-spectrum-analyzer/msg4848032/#msg4848032 (https://www.eevblog.com/forum/testgear/owon-xsa1032-tg-3-2g-spectrum-analyzer/msg4848032/#msg4848032) it is the same, there OWON is grayed out from the label.
Compare those pictures with https://www.testequipmentdepot.com/owon-xsa1032-tg-9khz-32-ghz-spectrum-analyzer-with-tracking-generator-kit.html (https://www.testequipmentdepot.com/owon-xsa1032-tg-9khz-32-ghz-spectrum-analyzer-with-tracking-generator-kit.html)
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To all the colleagues that have been following this thread. The attachments are photos of the equipment in my lab that I've been using to conduct the experiments and tests described in previous posts. I hope this satisfies any curiosity or suspicion of any type of nefarious purposes :phew:. With that out of the way, I would like to continue sharing with like-minded electronics enthusiasts, my experiences, discoveries, and doubts, as I try to learn and attempt to master new concepts and equipment :-\.
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Residual FM Test
I've been curious about this spec since it isn't even mentioned on the XSA1032 manual or datasheet. So I got some information on what it means and how to test it (attachments 2 and 3), but I'm not sure I fully understand the steps. Particularly, when they say to use the peak-to-peak search function. I experimented with Peak Max Search and Peak Min Search, but it doesn't give consistent results. So finally I decided to instead use a Delta Marker spanning the full Sweep time. This is more stable, especially after I increased the Sweep time to 400ms, but the dB reading still constantly changes, although more gradually. For the calculations I picked the highest number I saw after a few minutes, but again, it's possible that this is not much better than a random number, since I'm not, or don't know how to follow the instructions to the letter.
For the Demodulation Sensitivity I'm using the values from attachment 4:
2800/18.49 = 151.4 Hz/dB
Notice that I'm using an RBW of 5kHz, even though the specs for the Rigol SA calls for 1kHz. I had to go with a minimum of 5kHz, because on this SA any less than that causes the Zero Span function to gray out, and the next steps calls for setting the SA to Zero Span.
For the Frequency Deviation I'm using the setup shown on attachment 5, and waiting a couple minutes while eyeing the dB value to record the highest value that pops-up:
0.19 dB
So the residual FM comes to: 151.4 x 0.19 = 28.8 Hz
Of course, this number is more likely than not off. Even if the procedure I used turns out to be close enough to what's required, the Residual FM of the signal generator I'm using (Windfreak SynthUSBII) is not specified. So, as stated in the instructions, it may influence the final result.
I'd be grateful if anyone with better knowledge of this test helps clarify the instructions!
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Second Harmonic Distortion Test Part 1
The following is my interpretation of this test after reading a number of articles regarding this subject, hope I've got it right:
This test is used to determine the dBc value of the second harmonic generated by the SA while a fundamental signal is being applied at the SA's input. To get a valid reading the signal generator should be capable of producing a signal nearly free of harmonics, particularly the 2nd harmonic. To help achieve a harmonic free signal before applying it to the SA's input, an appropriate low pass filter can be used between the generator and the SA. Ideally, the low pass filter would only block the harmonics, particularly the 2nd harmonic.
The SA manufacturer's specs may be given as a dBc value when the specified fundamental is at the specified dBm level, for example, on the XSA1032 the Second harmonic distortion is specified as -65dBc when a -10dBm harmonic free ≥ 50 MHz fundamental is applied to the SA's input. This means, that although the input signal contains no harmonics, up to a -65dBc 2nd harmonic may appear on the SA's screen that was solely generated by the SA's internal circuits.
Alternatively, the SA manufacturer's specs may be given as an SHI value when the specified fundamental is at the specified dBm level, for example, on the DSA832E the Second Harmonic Intercept (SHI) is specified as +40dBm when a -20dBm harmonic free ≥ 50 MHz fundamental is applied to the SA's input.
The SHI value is a theoretical dBm level at which the fundamental's and 2nd harmonic's dBm levels coincide. Normally, this can't be achieved in practice. However, is a known fact, that as the fundamental's dBm level increases the 2nd harmonic dBm level also increases with a 2:1 ratio. Using this fact, the level where both signals would theoretically coincide can be easily calculated mathematically or graphically. I added information to the original XS1032 & DSA832E specs showing how to mathematically convert an SHI to a dBc value or a dBc value to an SHI, see attachment 1.
Attachments 2 and 3 comprise one of the more relevant articles I read regarding this subject.
Attachment 4 is graphical representation I put together illustrating how the XSA1032 & DSA832E SHI's can be obtained graphically.
I don't have a generator that meets the requirements necessary to properly evaluate the XSA1032 Second Harmonic Distortion, but on the second part I'll post the results obtained with the generators I have.
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Second Harmonic Distortion Test Part 2
To test the 2nd Harmonic Distortion on my XSA1032-TG, first I'm going to use my SynthUSBII signal generator. Attachment 5 shows the harmonic content specs for the main IC chip used in this generator. Since this generator's output is a square wave, the 3rd harmonic spec is a larger value than the second. But even the second harmonic spec is larger than the value required to get a valid reading of the SA's harmonic distortion. To perform the test the generator's output was set to 50MHz at approximately -10dBm (the output level is not calibrated).
For Attachments 6 & 7 the SA's span was set to 160MHz to allow to see the relative values of the fundamental and the 2nd & 3rd harmonics. The 2nd harmonic should be at marker 2, but with the current settings the noise floor is too high for it to be visible. I can't lower the noise floor because the SA won't let me set the Ref Level and the Attenuation to the values required for the test.
For attachment 8, to zero in on the 2nd harmonic, the SA's span was set to 100kHz and the center frequency to marker 2. Here the 2nd harmonic is visible because the noise floor is much lower. Since only a small signal is in the sweep's range, I was able (allowed by the SA) to set the Ref Level and the Attenuation to the values required for the test. The 2nd harmonic dBm value is around -62, since the fundamental is around -9dBm, the dBc value comes to -62 -(-9) = -53dBc. This is not even close to the -65dBc cited on the XSA1032-TG specifications, but that requires that the input signal be nearly harmonics free, which it isn't in this case.
Next I want to test the 2nd Harmonic Distortion on my XSA1032-TG using my AG1022F AWG. Attachment 9 shows the harmonic distortion specs for this generator which are much better than the ADF4351 specs. However, I'll have to perform the test with a 25MHz fundamental instead of the ≥ 50 MHz that the XSA1032 specs call for. Unfortunately, 25MHz is the highest frequency that my AG1022F can output. To perform the test the generator's output was set to 25MHz at 200mVpp. On a 50-ohm system 200mVpp is equivalent to around -10dBm.
For Attachments 10 & 11 the SA's span was set to 100MHz to allow to see the relative values of the fundamental and the 2nd & 3rd harmonics. The harmonics should be at markers 2 & 3, but with the current settings the noise floor is too high for them to be visible. I can't lower the noise floor because the SA won't let me set the Ref Level and the Attenuation to the values required for the test.
For attachment 12, to zero in on the 2nd harmonic, the SA's span was set to 100kHz and the center frequency to marker 2. Here again the 2nd harmonic is visible because the noise floor is much lower. Again, since only a small signal is in the sweep's range, I was able (allowed by the SA) to set the Ref Level and the Attenuation to the values required for the test. The 2nd harmonic dBm value is around -70, since the fundamental is around -10dBm, the dBc value comes to -70 -(-10) = -60dBc. This is closer to the -65dBc cited on the XSA1032-TG specifications, but still, the input signal is not nearly harmonics free as required, perhaps if I use an appropriate low pass filter I could get closer to a valid reading. Unfortunately, I don't have one at this time.
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Third-order intermodulation - Intercept (TOI) Test
I read several interesting articles regarding this subject and found that although different looking formulas are used to derive the TOI, they are just that, different looking. In essence, they are all describing the same thing. Attachments 1-3 are a sampling of the most relevant articles I used as reference.
The SA manufacturer's specs for the test are in attachment 0, the test description that I used to perform the test is on attachment 4. The manufacturer's specs call for a ≥ 50 MHz two tone input at -20dBm with a 100kHz separation between the tones (signals). I couldn't use 50MHz since I'm using my AG1022F generator that maxes out at 25MHz. This is a dual output generator, so I set channel 1 to 25MHz and Channel 2 to 24.9MHz.
The test instructions (attachment 4) call for a "Power Coupler", also known as a combiner, to connect the generators to the SA. I don't have a combiner, instead I used a BNC T coupler and two cables to make the connection (see attachment 6). This is not optimal but is allowed for lower frequencies (although 25MHz isn't that low). To keep the 50-ohm system as intact as possible, I changed the setup of the generator's outputs to 25-ohms. This should result in a 50-ohm combined output to match the SA's 50-ohm input.
Attachment 5 is a screen from one of my favorite dB calculators. It shows that for a -20dBm output about 63mVpp are required. I started out my generator's outputs at that level, but to get the -20dBm required by the specs I had to increase the level a little, -70dBm on channel 1 and -67dBm on channel 2.
Attachments 7 and 8 show the spectrums of the two fundamentals and the intermodulation products 2f₂-f₁ and 2f₁-f₂ as indicated in the test instructions. There are other intermodulation products, but these ones are the closest to the fundamentals and for that reason the most problematic (can't be easily filtered) when present on a DUT. From the marker readings the TOI can be calculated. In the attachments, as I mentioned before, there are a number of different looking formulas for this, but they all give the same answer. So I'm going to use the one in the test Instructions.
TOI = Rl + [Ir₃/2]
Rl is the power level of the fundamentals, -20dBm.
Ir₃ is the distance between either one of the fundamentals and largest (smallest level) of the two intermodulation products (IMDs). I'm going to round that to 50dBM.
So we have -20 + [50/2] = +5dBm
Well, that's half the +10dBm that we are supposed to have according to the specs but given that the test conditions were far from optimal, I think I'll regard it as a pass!
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1 dB Gain Compression Test
I wasn't able to perform this test as specified. The main reason, as I see it, is that the SA has safeguards that prevent the user from manually setting certain parameters. As I understand it, the test calls for 0dBm attenuation and a ≥ 50 MHz input signal that shouldn't show the 1dB compression, nominally, before it's level reaches +2dBm (see attachment 1). So to see the signal, the reference level has to be higher than at least +2dBm, but the SA won't let me set the attenuation to 0dB unless the reference level is set a lot lower, -20dBm or lower.
In addition, although there is an abundance of information for performing this test on an amplifier, I couldn't find specific information on using the test to characterize the SA itself. The Fluke publication I've been using as a guide for other tests, has a write-up on a "Compression Test", but is a different test that deals with compression of an adjacent smaller signal when a larger signal is present. Attachment 2 is the complete Fluke pub in case some of you want to read it. Attachment 3 is a write up I found that in my opinion comes the closest to explaining the procedure and reasoning behind the test I wanted to perform.
The rest of the attachments deal with the procedure I envisioned to perform the test. Attachment 4 is the conversion table I used to set my generator at the appropriate dBm levels, my AG1022F only accepts pp values or rms values. Attachments 5 and 6 show the 25MHz fundamental at dBm values of 1 to 5dBm, I used different Traces and scattered them on the screen for better visibility by changing the Center Frequency before doing the Max Hold on each trace. The one thing I couldn't do is set the Attenuator to 0dB.
With the 25dB attenuator setting I didn't expect to see any compression, but if you look closely at the last two peaks, it appears as if compression is starting to creep in. I thought maybe this meant that there was some kind of non-linearity in the display, so I changed the reference level to 8dBm to see if there was a difference (attachments 7 and 8 ). But no, it's the same. I hooked up my DSO to check the signal mVpp values and it agreed with the SA. Seems that either there is loss on the cables, or my generator is not quite outputting the calibrated values.
So that's the best I could do! But please, if any one of you has any insights or opinions on how to do this test correctly, post it.
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Resolution Bandwidth Test Part 1
I found this test very interesting. Besides the test specs and test instructions (attachments 1 and 2), I read an articles that compares the performance of the analog filters used on older SAs, to the current digital filters (Attachment 3). On Part 2, I'll try to duplicate the example showing how the new digital filters allow the spectrums of very close adjacent carriers of different amplitudes to be viewed and analyzed and do so with much faster repetition rates than what could be achieved with the older generations.
The spec identifies the different RBW filters available (10Hz to 500kHz (1-10 steps by sequence), 1MHz, 3MHz). I did test the selectivity of each one of these filters, but I've only attached a sampling of the spectrums I obtained to illustrate the main things I found (Attachments 4-9). To check the "Bandwidth Selectivity", I didn't follow the Instructions on attachment 2 to the letter because this SA has an NdB Marker Function that allows the bandwidth at the dB level of interest to be determined automatically.
According to the spec, the "Resolution Filter Shape Factor (60 dB : 3 dB)", this is what the instructions call the "Bandwidth Selectivity", should be "<5: 1 typical". The instructions show that this is calculated using: f60dB / f3dB, for this to be less than 5, the 60dB bandwidth can't exceed the 3dB value by more than 5 times. It also states that the typical ratio is 1. I'm afraid that I never saw 1 on any of my measurements, 1 would mean that the 60dB and 3dB bandwidths are the same. As far as the ratio being <5, that checked out fairly good with some caveats. The details are as follows:
Edit: I didn't look at the punctuation close enough on "<5:1 typical", It's a colon, not a semicolon as I
thought, so it claims the ratio is <5:1 typical, which is OK, not 1 typical as I mistakenly interpreted it.
RBW = 10Hz: Attachments 4 and 5 show the 3dB and 60dB bandwidths. 143 / 10 = 14.3 not <5. So for RBW=10Hz the selectivity
is not as good as stated. With the span set to 500Hz, we have 50Hz per division. Notice that about half way between -60dBm
and -70dBm the bandwidth is about 50Hz, that would be the 35dB bandwidth of the filter and the point where we actually
have a 5 ratio. So the filter can still resolve different frequencies as specified but only for larger signals.
For all the remaining spectrums I'm not showing the 3dB bandwidth because I found out it's the same as the RBW setting or very very close. The next few possible RBW setting have an improved signal shape, and are closer to the stated spec, but still somewhat off. Starting with RBW = 50Hz specs are met for several possible settings.
RBW=50Hz" Attachment 6 shows the 60dB bandwidth, the 3DB bandwidth is the same number as the setting (50dB). 247 / 50 <5.
For the settings prior to 300Hz the specs are met, but starting at 300Hz the noise floor starts to get in the way. To get a 60dB reading with the current settings, the noise floor has to be less than -90dBm. But right at RBW = 300Hz this is no longer the case, and it gets worse from this point on, since the noise floor gets higher with every further increase in RBW.
RBW = 300Hz: Attachment 7 shows the 60dB bandwidth, the 3dB bandwidth is 300, 1700 / 300 = 5.66, not quite <5.
Even though the 60dB bandwidth can't be accurately determined on subsequent RBW settings due to the noise floor, the shape of the filter is still good, and if the bandwidth is measured just above the noise floor, the ratio between this higher level bandwidth and the 3dB level bandwidth is still <5. Attachments 8 and 9 are examples of this situation.
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Resolution Bandwidth Test Part 2
To get some idea of how the different RBW filters perform in real live, here i'm trying to recreate the example described on the "Agilent AN 1318 Optimizing Spectrum Analyzer Measurement Speed" article I attached to the previous post. Namely, to check the SA's performance when trying to visualize two CW signals that are 240Hz and 20dBs apart. In the article they use signals around 1 GHz at -35dBm and -55dBm, due to equipment limitations I'm using around 25MHz at -30dBm and -50dBm.
Attachment 10 contains the spectrums shown in the article as displayed by an Agilent 8563E SA at RBW=30Hz and RBW=100Hz with a 5kHz span. The equivalent spectrums on my XSA1032-TG are attachments 14 and 15.
Attachments 11 to 13 show the same signal using RBW=10Hz, here I tried span 500Hz, as well as the 5kHz span they used on the article. Notice that even at RBW 10Hz, the sweep time is nowhere near the 16.7 seconds it takes for RBW=30Hz at 5kHz span when using the older Agilent 8594E (Figure 5 in the "Agilent AN 1318 ..." article).
Attachments 16 and 17 show the same signals using the RBW=30Hz and 100Hz used in the article, but using a 1kHz span instead of the 5kHz span. I included these because it seems that the Delta measurements are a bit more accurate at this setting.