Another scope recommendation request with a twist. - Page 1
Forum section: electronics / testgear

author: RossH0755
author_rank: Newbie
timestamp: April 02, 2020, 01:50:10 am
content: Hi, all. Thank you for reading and responding to my post. I am retired and am getting deeper into my new hobby, restoring old tube radios, which would include shortwave. I am looking for an analog scope with 200+MHz, 1GS/s, and four channels. "Beginner" or "starter" anything isn't part of my vocabulary (it's no harder to learn on the best you can afford) and tend to over buy the first time rather than be sorry later. Budget? Let's say $800.00.Having said all that, if someone can make a good argument for DSO's for HF, I'm willing to listen. You're the experts, not me.Since the question seems to be asked a lot I'm in Central California.Thanks,Ross

author: stafil
author_rank: Regular Contributor
timestamp: April 02, 2020, 01:55:13 am
content: Having been through the same exercise myself recently, my advice is that you take into consideration if an oscilloscope can be hacked or not.

author: bob91343
author_rank: Super Contributor
timestamp: April 02, 2020, 03:14:58 am
content: I got my wonderful HP54542A for not much money a few years ago. Four channels, 500 MHz and lots of functionality. Yes it's obsolete, even uses floppy disc. But I haven't told it that so it thinks it's the latest.

author: tautech
author_rank: Super Contributor
timestamp: April 02, 2020, 04:22:09 am
content: Quote from: RossH0755 on April 02, 2020, 01:50:10 amAnalog scopes by definition don't do GSa/s.That's entirely a DSO's domain and a single 1 GSa/s ADC is inadequate to meet Nyquist using 4 channels at 200 MHz.For your disclosed requirements a DSO with good FFT could well be of use as a poor mans (please don't take offence) spectrum analyser.At your spending level SDS1104X-E hacked or its big brother SDS1204X-E could be well worth a look.If you want to see some FFT screenshots of frequencies you might work with please just ask.

author: jemangedeslolos
author_rank: Frequent Contributor
timestamp: April 02, 2020, 12:28:12 pm
content: [Mode ntcnico]GW Instek ?There is a youtube channel that may interest you : Kiss AnalogHe made some test on scope and he is very focused on audio.He made a review on GW Instek MDO-2204eg which combines a scope and a spectrum analyzer :There is a promo on this one :https://eleshop.eu/gw-instek-mdo-2074eg-oscilloscope.htmlI don't know if this scope is available at this price in US ?ntnico will probably have more info to unlock BW and options on this model.[/Mode ntnico]

author: nctnico
author_rank: Super Contributor
timestamp: April 02, 2020, 02:09:46 pm
content: I think I'll cancel my forum subscription... my work is done here..To add: the GW Instek GDS2074-E + hacking it with the key generator (to 300MHz on 2 channels) could be a consideration. That would also get the serial protocol decoders and the MDO functionality. OTOH the MDO-2204eg has an internal function generator. Don't know if bode plotting is possible though but last time I checked bode plotting on these oscilloscopes was not stellar anyway.I think the Siglent Tautech suggested is pretty much on par (the hardware is nearly identical) except that the GW Instek has individual channel controls instead of shared.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 02, 2020, 02:22:46 pm
content: If you're going to be poking around in old tube radios it might be worth getting some HV differential probes, to save you from letting out the magic smoke by accident too easily.That'll have a significant impact on your budget, as they aren't cheap.

author: 2N3055
author_rank: Super Contributor
timestamp: April 02, 2020, 02:26:28 pm
content: Quote from: nctnico on April 02, 2020, 02:09:46 pmLOL!

author: 2N3055
author_rank: Super Contributor
timestamp: April 02, 2020, 02:27:44 pm
content: Quote from: AVGresponding on April 02, 2020, 02:22:46 pmThis is good advice. Micsig makes cheapest decent HiVolt Diff probes..

author: jemangedeslolos
author_rank: Frequent Contributor
timestamp: April 02, 2020, 04:10:19 pm
content: Quote from: nctnico on April 02, 2020, 02:09:46 pmI figured that since Ross is retired, he may have less good eyesight and so he won't be put off by the ugliness of this scope

author: stafil
author_rank: Regular Contributor
timestamp: April 02, 2020, 06:57:33 pm
content: Quote from: jemangedeslolos on April 02, 2020, 12:28:12 pmIs there a hack for BW upgrade on MDO2074eg? Searching the forum couldn't find any

author: Tom45
author_rank: Frequent Contributor
timestamp: April 02, 2020, 08:41:06 pm
content: Welcome Ross,You asked about analog scopes and everyone is telling you about digital scopes.For analog scopes with 4 channels and >= 200 MHz, look at the Tek 2465x series, or the Tek 7000 mainframes.The 2465x scopes have limited capabilities for channels 3 and 4. So think carefully about whether you could live with that.The Tek 7000 scopes are very flexible with the variety of plugins available. An example would be a 7704 or 7904 mainframe with 2 7A26 vertical plugins and 7B80 and 7B85 for the horizontal.In both cases these are going to be used and quite old. So take some care in ensuring that you get a scope that is working.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 02, 2020, 09:33:56 pm
content: Quote from: Tom45 on April 02, 2020, 08:41:06 pmAnd especially in the case of the mainframe,bloody huge!A slightly outside the box idea might be a used scopemeter. I realise these are expensive for what they are, and I don't personally know any with more than 2 channels, but theyarefully isolated, removing the need for expensive differential probes (unless you're planning on probing the cathode on a CRT).

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2020, 09:38:37 pm
content: Quote from: RossH0755 on April 02, 2020, 01:50:10 amTwo points you need to consider.Firstly, what do you want to measure? You should understand the consequences that scopes' sensitivity and linearity will have on your measurements. Often radio tests are better done with frequency domain equipment like spectrum analysers plus a DMM.Secondly the scope probe cannot be saparated from the scope. You must use the appropriate type, and some will cost as much as your scope. Some information can be found in the references athttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: thm_w
author_rank: Super Contributor
timestamp: April 02, 2020, 09:45:46 pm
content: Quote from: Tom45 on April 02, 2020, 08:41:06 pmHe did also say 1Gs/s, which is not possible as far as I know..

author: bob91343
author_rank: Super Contributor
timestamp: April 02, 2020, 10:00:24 pm
content: My 4 channel HP 54542A claims 1 Gs/s and has 4 channels each 500 MHz. How is that possible? In fact I have looked at signals over 600 MHz with it. Of course I must beware of aliasing but otherwise it seems to violate some Nyquist criterion or something.

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2020, 10:05:45 pm
content: Quote from: bob91343 on April 02, 2020, 10:00:24 pmI have observed and triggered on 1.1GHz signals on my Tek 485 scope. Of course the amplitude was reduced.My 50kS/s scope can display 2GHz signals (140ps rise time).Extremes are possible, but not necessarily helpful nor representative.

author: tautech
author_rank: Super Contributor
timestamp: April 02, 2020, 10:09:30 pm
content: Quote from: bob91343 on April 02, 2020, 10:00:24 pmBecause it's a CRT based DSO.

author: tggzzz
author_rank: Super Contributor
timestamp: April 02, 2020, 10:12:07 pm
content: Quote from: tautech on April 02, 2020, 10:09:30 pmWhy is the display technology the key factor?Capture and display are orthogonal concerns.

author: nctnico
author_rank: Super Contributor
timestamp: April 02, 2020, 10:35:39 pm
content: Quote from: bob91343 on April 02, 2020, 10:00:24 pmRead the manual: it has equivalent time sampling to increase the effective samplerate but this only works for repetitive signals.

author: tautech
author_rank: Super Contributor
timestamp: April 03, 2020, 07:00:04 am
content: Quote from: tggzzz on April 02, 2020, 10:12:07 pmYeah sorry, went off on a tangent.Gurgling HP 54542A indicates it's a 2GSa's DSO and specs claim '2 GSa/s Sample Rate on 4 channels' which seems to indicate an ADC on each channel so Nyquist is comfortably met for 500 MHz.https://www.keysight.com/en/pd-1000001425%3Aepsg%3Apro-pn-54542A/4-channel-2-gsa-s-digitizing-oscilloscope-obsolete?cc=NZ&lc=eng

author: Electro Detective
author_rank: Super Contributor
timestamp: April 03, 2020, 08:14:22 am
content: Guys pleaseOP specified"...restoring old tube radios..."perhaps some discussion on SAFETY and isolation techniques/gadgets may be appropriate tooso OP does not BBQ any old tube radio/s, CRT or DSO oscilloscope, and him/herselfbefore they can type up a second post here..fwiw during this C palmdemic we need ALL newb members ALIVE and kickingto replace the millions of 'C' departed members so far

author: Fungus
author_rank: Super Contributor
timestamp: April 03, 2020, 08:26:20 am
content: Quote from: Tom45 on April 02, 2020, 08:41:06 pmThat's because he asked for "a good argument for DSO's", and, let's face it, DSOs are better than CROs in just about every way possible.(every way except looking cool)

author: nctnico
author_rank: Super Contributor
timestamp: April 03, 2020, 08:46:31 am
content: Quote from: Electro Detective on April 03, 2020, 08:14:22 amThat already got answered: a differential probe. The ones from MicSig are good and very affordable. Unless if the OP has a formal training and a special work place, isolation transformers are a no-go.

author: Electro Detective
author_rank: Super Contributor
timestamp: April 03, 2020, 08:52:39 am
content: Quote from: Fungus on April 03, 2020, 08:26:20 amDSOs still at the starting gate compared to CRTs, on real world troubleshoots below 100mhzJob done with CRT and DUT returned to customerbefore DSO finishes booting and or scrolling through Menu optionsand praying the programmed or shared channel Trigger isn't asleep on the job

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: April 03, 2020, 09:27:28 am
content: Quote from: Electro Detective on April 03, 2020, 08:52:39 amI've told you a million times not to exaggerate!

author: tggzzz
author_rank: Super Contributor
timestamp: April 03, 2020, 09:31:15 am
content: Quote from: tautech on April 03, 2020, 07:00:04 amI've never ever had a brain fart. Oh no. Never ever ever. Perish the thought

author: paul002
author_rank: Regular Contributor
timestamp: April 28, 2020, 07:27:54 am
content: Hi,I own a GW-Instek MDO 2072 and use it for HF and VHF projects. I use mostly the spectrum analyser option which runs to 500 Mhz. It also has a function generator which runs till 25 Mhz. It works quite well but the spectrum analyser is a extended FFT that is it looks like and works like a real spectrum analyser but uses FFT to generate the picture. For HF and VHF work (till 146 Mhz) it works good but you have first to use the scope to get a good signal and then put it to spectrum analyser. Some times when the signal is to strong you get wrong result in the spectrum analyser. Thats why I first check the signal in scope function. The one thing that is lacking is that the functiongenerator cannot function as tracking generator. That would have been great, but I now use a nanovna for that.So if you are on a low budget and need a scope / spectrumanalyser this is a bargain. If you have 2k to spare I would consider two seperate instruments. But I have lots of fun with this scope.