Looking for a digital oscilloscope for amateur radio use - Page 1
Forum section: electronics / testgear

author: opto_isolator
author_rank: Newbie
timestamp: January 26, 2019, 02:21:03 am
content: I am looking to use an oscilloscope with an RF de-modulator, and sampler on X and Y to monitor my transmissions, signal, as well as to validate that my amplifier is tuned correctly using a standard trapezoid pattern. I am hearing that digital scopes need to have certain features to work correctly (such as having an intensity grading display). I was looking at the digital oscilloscope comparison Spreadsheet and found the Siglent SDS1202X-E, which shows that it has a 200MHz bandwidth, 1G Sa/s, and a 256 level grading display.Would this scope be able to handle such a task? I plan on using this up to 28MHz (10M band), with my 1000W AL-80B Ameritron amplifier.Any feedback would be appreciated!Thanks

author: vk6zgo
author_rank: Super Contributor
timestamp: January 26, 2019, 03:02:47 am
content: Quote from: opto_isolator on January 26, 2019, 02:21:03 amDSOs can do stuff like that, but their XY displays aren't usually that spectacular.They have improved over the years, but it doesn't seem to have been a priority.The intensity grading facility would make looking at a normal AM modulated signal (or SSB with two tones)better, but I'm not so sure it is necessary for a trapezoid pattern.I don't have a DSO, & have only done such tests with an analog 'scope, but some folks may have done them with a DSO.

author: tautech
author_rank: Super Contributor
timestamp: January 26, 2019, 03:37:26 am
content: I instantly remembered this thread doing just what you want to do with a SDS1202X-E but sadly the excellent video is no longer linked:https://www.eevblog.com/forum/testgear/sds1202x-e-as-a-ham-station-monitor/Maybe post a message there or PM member borjam to see if can relink the video or offer advice.

author: opto_isolator
author_rank: Newbie
timestamp: January 26, 2019, 03:45:38 am
content: Thanks for the responses. I saw that thread too. I'm guessing it was linked to a Youtube video that was removed. I'll see what they say!Travis

author: Fungus
author_rank: Super Contributor
timestamp: January 26, 2019, 10:59:59 am
content: Quote from: opto_isolator on January 26, 2019, 02:21:03 amYes.Also: The slightly cheaper Rigol DS1054Z does a really good intensity graded display and has four channels.

author: opto_isolator
author_rank: Newbie
timestamp: January 26, 2019, 04:28:40 pm
content: Thanks for the response. My concern would be the 1Gsa/s sample rate. Obviously 2Gsa/s is better, but would 1Gsa/s still show everything I'd need to see?

author: Fungus
author_rank: Super Contributor
timestamp: January 26, 2019, 05:45:57 pm
content: Quote from: opto_isolator on January 26, 2019, 04:28:40 pmWith a 28MHz sinusoidal input? No problem at all. Digital oscilloscopes use sin(x)/x reconstruction filters to recreate signals on screen. Anything over 56MSa/s would be enough in theory and 100MSa/s would be plenty in practice.This video explains it all beautifully:There's notmuchdifference in price between Rigol/Siglent though. If you were interested in anything digital things then having only two channels would be a showstopper. Can you imagineeverneeding more than two channels? If not then take your pick.

author: tautech
author_rank: Super Contributor
timestamp: January 26, 2019, 06:34:29 pm
content: Quote from: opto_isolator on January 26, 2019, 04:28:40 pmThen maybe the new 2000X-E's might interest you:https://www.siglentamerica.com/digital-oscilloscopes/sds2000x-e/Bit more $ but you get all the stuff the 4ch X-E's can do but with 2 GSa/s and 28M of memory.$ 619 for a 2GSa/s 200 MHz 2ch DSO that potentially can be hacked to 350 MHz seems pretty attractive to me.I've just got some and having a look at them when I find time.....summer here and many outside jobs calling.Yes I must find time to compare 1kX-E and 2kX-E XY modes.

author: nctnico
author_rank: Super Contributor
timestamp: January 26, 2019, 07:10:35 pm
content: Quote from: opto_isolator on January 26, 2019, 04:28:40 pm1Gs/s is way overkill for a 28MHz signal. Google Nyquist. In reality you'll need some extra room in the bandwidth for an anti-aliasing filter. With that factored in 100Ms/s would be more than enough for your application. Sampling at a higher frequency means you'll just fill the memory with useless information.

author: w2aew
author_rank: Super Contributor
timestamp: January 26, 2019, 08:15:54 pm
content: As stated earlier, the XY display mode on most DSOs really pales in comparison to the good old analog scope. I've never used the Siglent in question, so really can't comment on that.Another thing to take a look at is the available memory and sampling modes. It's fine to look at the max sample rate of 1GS/s, but if you want to look at the RF envelope using just the RF sampler, the story changes a bit. To get a decent picture of the envelope of a voice modulated signal (AM, SSB, etc.), you'll need to have the horizontal scale somewhere around 1ms/div, thus a 10ms long acquisition. The waveform memory will determine what the effective sample rate will be. For example, if you use a 10,000 point waveform record, the effective sample rate of the waveform will be 10,000 Samples divided by 10ms, or just 1MS/s - which is clearly insufficient to accurately capture the 28MHz RF signal. In other words, it will alias it and not give you a meaningful look at the RF envelope. You'd need to have at least a 1M record length so that the 10ms capture has an effective waveform sample rate of 100MS/s to sufficiently sample the RF.Of course, many scopes have different sampling modes (Peak detect, etc.) that can help avoid these problems, but you'd have to make sure that the appropriate sampling mode is compatible with the intensity grading in order to get a decent looking RF envelope.Sometimes it's just hard to beat a good old analog scope for looking at XY displays, RF Envelopes, trapezoid patterns, etc.

author: opto_isolator
author_rank: Newbie
timestamp: January 26, 2019, 09:11:45 pm
content: Hi Alan - I see you found my post that I made hereThanks for your response, your feedback is extremely valued!!The SDS1202X-E spec sheet lists that it has 14M points of memory available, which would be shared between channels if both channels are used. There are 4 different sample methods listed in the manual - normal, peak, average, and high resolution. I can't seem to find posts here from anyone that has successfully used this specific scope for my intended use (but then again I can't seem to find any real videos other than yours that demonstrate the use of a digital oscilloscope for what I am looking to do, and your scope has much more horsepower than anything in my price range).For the price I think I'm going to try one and see how it works out.

author: Fungus
author_rank: Super Contributor
timestamp: January 26, 2019, 11:45:50 pm
content: Quote from: opto_isolator on January 26, 2019, 09:11:45 pmIt will definitely work, 100% confidence level.

author: jiangtao.lv
author_rank: Regular Contributor
timestamp: January 27, 2019, 02:15:02 am
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: borjam
author_rank: Unknown
timestamp: January 27, 2019, 11:42:35 am
content: Quote from: tautech on January 26, 2019, 03:37:26 amThank you! I guess you found it excellent thanks to my laughable "Broken Engrish"Now, seriously. The video was deleted by Vimeo because I didn't renew my premium subscription. I'll try to locate the original material.The point was, anyway, to show how a digital scope can be useful for a ham. Many old timers claim that only analog scopes are up to the task. In the case of a digital scope, the roll mode is actually much better than the trigger mode for envelope monitoring. I recorded the test using a SDS1202X-E hooked to the sampling output of a dummy load and a Yaesu FT-817nd portable transceiver.The Siglent is better than the Rigol for this application because it allows to use roll mode with faster timebases (I think 50 ms/div) which allows the operator to see a more detailed envelope. The fastest the Rigol supports is like 200 ms/div if I remember correctly. I think I explained it on a post here.

author: nctnico
author_rank: Super Contributor
timestamp: January 27, 2019, 11:48:02 am
content: Wouldn't a spectrum analyser or scope in FFT mode with a waterfall display be an option for this purpose? You'd see both the envelope and spectrum.

author: Adrian_Arg.
author_rank: Frequent Contributor
timestamp: January 27, 2019, 01:42:56 pm
content: Hello friend, I did the test with my FT757, when watching this video, with the only difference that I have a Rigol DS1054, released, and it worked perfect.in spanishHola amigo, yo hice la prueba con mi FT757, al ver este video, con la unica diferenciaq que yo poseo un Rigol DS1054, liberado, y me funciono perfecto.

author: GreyWoolfe
author_rank: Unknown
timestamp: January 27, 2019, 04:07:09 pm
content: I use a GW-Instek GOS 6112 to monitor my transmissions. Under $100 USD shipped when they first hit the market from ITT.

author: opto_isolator
author_rank: Newbie
timestamp: January 27, 2019, 07:56:52 pm
content: Alan did a good video a while back to show the difference between the XY modes in analog and digital scopes:Then this guy does a good job to illustrate the differences of XY modes between some cheap scopes. Even though the screen is compressed on the Siglent, I'm very impressed how good of a job it does once the settings are adjusted:

author: borjam
author_rank: Unknown
timestamp: August 25, 2019, 06:25:27 pm
content: Very very late (and the video is a bit silly, I should have prepared it much better, this is a one shot thing) but I found the original materlal.I've put it on Dropbox.https://www.dropbox.com/s/bpnmue4tdrm89uq/StationMonitor.mov?dl=0Have fun and don't laugh much. And I know, the uncorrected tungsten light is ghastly!