Buying a scope for measuring RF waveforms - Page 1
Forum section: electronics / testgear

author: Mike99
author_rank: Frequent Contributor
timestamp: November 01, 2023, 10:37:14 am
content: Dear expertsI'm a radio amateur and my main use for a scope is to measure AF and RF waveforms up to 50MHz. I rarely need to examine logic waveforms.I currently have a venerable Tektronix 2340A which does the job but is big, heavy and noisy and I'd like to replace it with something new.I'm only a couple of miles from a major UK supplier of test equipment, including Siglent, Rigol and Micsig scopes, and the Siglent SDS 1202X-E is looking attractive. I only need 2 channels and don't want to spend more than £400.Not being a scope expert I'd like to hear your opinions on whether this will suit my requirements.Thanks!Mike

author: tszaboo
author_rank: Super Contributor
timestamp: November 01, 2023, 10:48:27 am
content: What's the reason you would want an oscilloscope for such a job, instead of a spectrum analyzer? That's usually not the right job for that task, even if it has FFT, the signal levels for a scope is much higher, the dynamic range is much lower, you don't have 50 Ohm termination on the low frequency scopes, the input capacitance is high and so on. I would guess even an SDR would be better, or a low cost spectrum analyzer.

author: tggzzz
author_rank: Super Contributor
timestamp: November 01, 2023, 10:59:56 am
content: Quote from: Mike99 on November 01, 2023, 10:37:14 amMeasure what, exactly?frequency? A frequency counter will give more accurate results fasteramplitude? Scopes are only 2% vertical linearity, at best. To that add the effects of the scope's frequency response, the probing technique (especially resonance), scope VSWR (probably 1:1.3, i.e. >2dB) Better to use a power meter or spectrum analyserpower? See amplitude, especially for low powersharmonics? Not a chance with a scope due to non-linearity and/or ADC resolution. A spectrum analyser is much more appropriate.modulation? What type, e.g. amplitude, phase, frequency? FM/PM better with a modulation domain analyser which showing frequency vs time. Or an SDRSummary: a scope is a time-domain instrument. RF measurements are usually frequency domain and lower power. Choose the right tool for the job.Personally, if I had a working scope that does the job, I would spend my money on something that gave menewand different andinterestingcapabilities.

author: Mike99
author_rank: Frequent Contributor
timestamp: November 01, 2023, 01:12:39 pm
content: I already have an SDR with spectrum analyser software, frequency counter, modulation meter, RF millivoltmeter and a power meter. I'm interested in every day general measurements of peak-to-peak amplitude, noisy waveforms, 2-tone tests of SSB transmitter linearity etc. Nothing fancy.Mike

author: nctnico
author_rank: Super Contributor
timestamp: November 01, 2023, 01:13:50 pm
content: AFAIK the SDS1202 gives you the most bandwidth for your money.

author: tszaboo
author_rank: Super Contributor
timestamp: November 01, 2023, 02:26:14 pm
content: Quote from: Mike99 on November 01, 2023, 01:12:39 pmAll these are typically measured on a spectrum analyzer. Try to borrow a TinySA or a used SA to see how it does it. Or the TinySA is like 70 EUR, hard to go wrong with that.