Looking for advise on DSO or maybe i shouldn't be considering one ? - Page 1
Forum section: electronics / testgear

author: Wonka68
author_rank: Contributor
timestamp: July 14, 2021, 02:00:14 pm
content: Having been out of the hobby for over 30 years, i need some advise on test equipment.I want to get back into working on 10/11 meter radios and amps and try my hand at tube equipment.At this point its like starting over and trying to remember what ive forgotten.After reading other threads on the subject, some say that looking at modulation of RF carriers is better left to old analog scopes.I dont know if thats really the case or not.Fortunately im more able to afford the correct equipment now then i was 30-40 years ago when all i had was a transistor tester / volt meter and a watt meter.That being said, i need opinions on what DSO to buy.I have an old HP analog scope somewhere. I have not found it yet. Its most likely a 20mhz 2 channel but im not sure. And to be SURE im a rookie with a scope and considering what ive forgotten, a rookie on ALL of it.Is there any instance when i would need more than 2 channels @ 100Mhz bandwidth ?Im looking at the Siglent 200mhz 2 channel SDS1202X-E or the Siglent 4 channel 100mhz SDS1104X-E .An advantage for old eyes is the 1104xe has a built in web server to do almost real time on a big monitor via RJ45 Ip connection.I am also buying the Siglent SSA3021X-TG Spectrum Analyzer with tracking generator.For $1400 with a tracking generator, it seems a no brainer compared to paying that and more for a 30 year old one on fleabay.Im going to assume that most of the no name scopes that have a built in signal generator or wave form generator are pretty much crap.Im also on the hunt for a stand alone SINAD meter of some kind and an old school Variac.The china variac's on amazon have some glowing reviews and some that say it caught on fire.I just picked up a bird 43 with 3 slugs and a 1x2x5 peak kit with a bird kilowatt RF sampler and an Agilent 34401A bench DVM.Im going to attempt to do it the right way this time.All opinions and advise appreciated.

author: Wonka68
author_rank: Contributor
timestamp: July 14, 2021, 03:44:31 pm
content: I did find my analog scope. Its an HP 1980B. Still looking online for the specs.Maybe, if it works, i can serve as my analog scope. Just need to find the specs.

author: perdrix
author_rank: Frequent Contributor
timestamp: July 14, 2021, 07:01:33 pm
content: If you're 'scoping high voltage valve (tube) stuff, then I'd suggest you stay with the older analog 'scopes. Some modern DSOs will only tolerate very low voltages on their inputs (I've seen as low as 20V peak for damage levels on the 1M input - i.e. 200V with a 10:1 probe). The DSOs are great for low voltage stuff.D.

author: nctnico
author_rank: Super Contributor
timestamp: July 14, 2021, 07:08:37 pm
content: Quote from: perdrix on July 14, 2021, 07:01:33 pmNot true. Some specialised USB or low end DSOs (tens of dollars price range) may have low input voltage ranges but regular DSOs from A and B brands are typically rated to withstand 300V (IOW: no damage when connected to 230 VAC mains directly).

author: TimFox
author_rank: Super Contributor
timestamp: July 14, 2021, 07:29:27 pm
content: When looking at modulated RF waveforms, I personally find it more convenient to avoid the latency inherent in digital DSOs and use my older analog CROs. If I want to freeze a single sweep to measure voltages and times for documentation, I use a DSO. I started out at a tender age with CROs, and became adept at using the delayed time base and other trigger features. With some DSOs, you need to be careful to avoid aliasing of the waveform due to insufficient sampling: I once tried to chase down an apparent near-60 Hz waveform, that was not line-synchronous, on a good DSO, only to find that I was actually picking up a clean 10 MHz clock waveform, that was only 6 ppm different from the DSO's internal 10 MHz clock, giving an approximate 60 Hz alias, that was clear as a bell with the DSO horizontal set appropriately to see 60 Hz.

author: David Hess
author_rank: Super Contributor
timestamp: July 14, 2021, 08:01:14 pm
content: Quote from: Wonka68 on July 14, 2021, 02:00:14 pmMany digital storage oscilloscopes can do an acceptable job but most will not look as nice as an analog display. Oscilloscopes are not really suited for measuring RF carriers anyway.Quote100 MHz, or even lower, and 2 channels plus a trigger input cover a majority of applications. I would expect to be probing more AF, IF, power supply, and control circuits than RF circuits.QuoteI am sure someone can suggest some inexpensive sound card software and hardware which will make better audio measurements than required for radio applications.QuoteI would not hesitate to buy a used or NOS variac. There is not much to go wrong with them and normal wear can be refurbished.

author: Fungus
author_rank: Super Contributor
timestamp: July 14, 2021, 08:15:25 pm
content: Quote from: perdrix on July 14, 2021, 07:01:33 pmThe Rigols and Siglents have a 200V CAT rating printed on the front. A 10:1 probe will allow up to 2000V input so the 'scope should be perfectly OK with a few hundred volts.More than that? Get a 100:1 probe...nb. I'd get a fixed, non-switching 10:1 probe just to avoid mishaps.

author: TimFox
author_rank: Super Contributor
timestamp: July 14, 2021, 08:55:15 pm
content: Quote from: David Hess on July 14, 2021, 08:01:14 pm

author: Martin72
author_rank: Super Contributor
timestamp: July 14, 2021, 09:12:38 pm
content: Hi,QuoteOr 400V, in the case of siglent scopes - But be aware of the CAT ratings.QuoteNot really...As I said, be aware if the CAT ratings, for example:https://www.batronix.com/shop/measurement/probes/Rigol-RP5600A.html300Vac.....Which makes sense, because it´s a matter of the isolation of the probe, the distance between potentials inbetween and finally the maximum voltage capability of the resistors in there.So always have a look at the ratings of the probe FIRST.For safety reasons in general, at a higher voltage then the CAT rating of the scope, I would recommend a differential probe like this one:https://www.batronix.com/shop/measurement/probes/Micsig-DP10013.html

author: David Hess
author_rank: Super Contributor
timestamp: July 14, 2021, 09:13:41 pm
content: Quote from: Fungus on July 14, 2021, 08:15:25 pmBe very careful about the input voltage rating with common attenuating probes. Almost all 10x and 100x probes rely on the 1 megohm input resistance of the oscilloscope to attenuate DC so depending on exactly how AC coupling is implemented, it may allow the full DC voltage at the tip of the probe to be applied to the oscilloscope input without attenuation. (1)This means that the oscilloscope's input voltage rating applies to the tip of the probe whether the probe attenuates or not. Whether your oscilloscope is an exception to this is not specified by the manufacturers unless they happen to provide detailed schematics, which of course they no longer do, and I wouldn't trust asking them either.(1) There exist probes with series and shunt attenuation which can be identified by their lower input resistance, but they are very rare. 1000x probes are built this way, but very few 100x probes, and no current 10x probes that I know of.

author: tautech
author_rank: Super Contributor
timestamp: July 14, 2021, 11:25:45 pm
content: Wonka68, some comments FWIW;10/11m ~25 MHz is hardly demanding for modern DSO's however as you would like to port to a larger display and would also like a inbuilt FG maybe a SDS2104X Plus with its 10" touch and mouse capable display, inbuilt 50 MHz FG and 2 Mpts FFT might cover most of your needs.Still, if you prefer 2 instruments a SSA3021X Plus is just a little more than the older X series and really the one to get for the few additional features they have.WRT Siglent DSO input ratings all their DSO's have 400Vpeak rated inputs with a CAT1 rating although like others mention it's wise to use higher rated probes on elevated voltages for personal and equipment safety.

author: Wonka68
author_rank: Contributor
timestamp: July 15, 2021, 01:38:49 pm
content: I'm going to tread VERY lightly when it comes to the tube stuff as I have next to zero experience with tube based eq.I know enough to know that it can kill you in the blink of an eye if you are not careful.

author: Wonka68
author_rank: Contributor
timestamp: July 15, 2021, 01:41:58 pm
content: A guy on facebook marketplace has an old variac at 15A that's a monster and he wants $100 for it.I'll have to drive 2.5 hours south to get it if I want it.

author: Wonka68
author_rank: Contributor
timestamp: July 15, 2021, 01:49:42 pm
content: Quote from: tautech on July 14, 2021, 11:25:45 pmThe SDS2104X is sweet and includes a FG but is most likely overkill for the stuff im going to do. Considering the price, I think I can get a decent 2 channel 100 / 200 MHz scope and a generator cheaper.I did not know that the Siglent SSA3021X Plus even existed. Im trying to figure out now what the $200 difference gets you.Looking at the specs , I don't see much difference. Im still trying to figure out what the PLUS does differently. I dont mind the extra $200 if its justified.I just have to figure out what its doing differently.

author: Wonka68
author_rank: Contributor
timestamp: July 15, 2021, 01:56:08 pm
content: Quote from: tautech on July 14, 2021, 11:25:45 pmfound the differences with the plus versionim not sure I will see a $200 benefit from those features. but I could be wrong.

author: Wonka68
author_rank: Contributor
timestamp: July 15, 2021, 02:06:17 pm
content: Quote from: tautech on July 14, 2021, 11:25:45 pmWHOOPS, I should have kept watching before making the previous comment. If im not completely stupid, the $200 extra for the PLUS model of the 3021x is definitely worth it.Thank you for bring it to my attention.

author: Performa01
author_rank: Super Contributor
timestamp: July 15, 2021, 02:14:05 pm
content: Quote from: Wonka68 on July 15, 2021, 01:49:42 pmWell, it's a tough call. Of course, a cheap 1202X-E would fit your bill, but if you can afford it, the 2000X Plus series is a whole different world. Whether or not you can appreciate it, I don't know.Btw, don't worry about using high voltage probes. All Siglent SDS1000X(-E, -U), 2000X(-E, Plus) and 5000X frontends have a constant 1 MOhm input impedance down to DC, also in AC coupled input mode. Everyone can check this with a multimeter quite easily. Apart from that I guess only the crappiest toys or really old boat anchors might be different in that regard.Quote from: Wonka68 on July 15, 2021, 01:49:42 pmThe Plus is a big plus (pun intended) and easily worth the premium. It might just not be that obvious...

author: bdunham7
author_rank: Super Contributor
timestamp: July 15, 2021, 02:25:39 pm
content: Quote from: Wonka68 on July 15, 2021, 01:49:42 pmSDS1104X-E + SDG2042X makes a good combo, especially if you do a bit of modification--which is explained elsewhere on the forum. The built-in FGs are weak tea compared to a separate AWG.

author: Wonka68
author_rank: Contributor
timestamp: July 15, 2021, 03:51:49 pm
content: Quote from: tautech on July 14, 2021, 11:25:45 pmCant thank you enough on the heads up on the Siglent SAA30xxx plus series.I just bought the SAA3015x Plus straight from Siglent for $1295 with free ship.Thats $100 cheaper than the saa3021x with way more features. I know it has less bandwidth but for me 1.5gig is good enough. Especially for a guy thats going to be under 30mhz 99.99% of the time.Now to find the best bang for the buck on a 2 channel 100mhz scope. Even though its a 200mhz scope, I think its going hard to beat the 1202xe from siglent.

author: tautech
author_rank: Super Contributor
timestamp: July 15, 2021, 08:25:48 pm
content: Quote from: Wonka68 on July 15, 2021, 03:51:49 pmHold up a tick !SDS1202X-E was the very first of the X-E series and does not have all the features of later models.If you want those....webserver, Bode plot, WiFi and MSO then SDS1104X-E or SDS2202X-E are better models.

author: Wonka68
author_rank: Contributor
timestamp: July 16, 2021, 12:49:27 am
content: Quote from: tautech on July 15, 2021, 08:25:48 pminteresting you mentioned that as i have a SDS1104X-E in my cart on amazon. i just didnt think i needed 4 channels and it does cost more than the 1202.I was not aware that the 1202 was old techTY

author: tautech
author_rank: Super Contributor
timestamp: July 16, 2021, 01:11:45 am
content: SDS1*02X-E was to be available in at least 2 BW's when Dave (EEVblog) got a pre-release SDS1102X-E but when he hacked on video for all to see Siglent then only released it in the 200 MHz version.It's still a competitively spec'ed and priced DSO in this class but not with all the fruits of the 4ch X-E's but more than those in the more recent SDS1104X-U.Datasheets and manuals study will show the devil is in the detail.