oscilloscope recommendations for 160Mhz RF faultfinding - Page 1
Forum section: electronics / testgear

author: smiffy68
author_rank: Newbie
timestamp: February 04, 2015, 11:12:57 pm
content: firstly, go easy on me this my first post here.I've recently taken on some work repairing and testing some RF kit that operates around 160MHz and I'm in the market for a new scope. As the last scope I bought is now approaching 25 years old, (an early Hameg DSO), I now find myself with brands and functions I've never even heard of!Anybody got any recommendations based on hands on experience?Dual channel is sufficientThe amount of use it will get isn't huge, so I don't have a "Tektronix" budget.cheers smiffy

author: tautech
author_rank: Super Contributor
timestamp: February 04, 2015, 11:35:00 pm
content: Welcome to the forum.Just to put another brand in front of you.http://www.siglent.com/ENs/pdxx.aspx?id=25&T=2&tid=1Models to 300MHzhttps://www.eevblog.com/forum/testgear/review-siglent-sds2304-a-comparison-of-features-with-rigol-ds2000-series/

author: Howardlong
author_rank: Super Contributor
timestamp: February 04, 2015, 11:43:11 pm
content: If I understand correctly, the RF gear you have transmits and receives around 160MHz, or is this the baseband bandwidth?Assuming the former, I'd suggest that a time domain instrument like a scope has limited use for RF. While you can do things like peak filters with a scope, sometimes it's better to use a frequency domain instrument. Although you can do limited frequency domain work with your average scope these days, it's of limited practical use.What sort of signals are the baseband, and is it digital or analogue? What kind of modulation?If it's marine band stuff, typical at around 160MHz, I'd suggest a conventional communications test set would be a very worthwhile instrument to use for testing and repairing such kit. Used units like a Marconi 2955 used to go for about UK £450 or so (perhaps $650). They're CRT units but they work pretty well if treated right. I've had to repair mine once in about 14 years, the line output transformer driver transistor went south.There are other options, but a lot of test sets were designed for the cellular age and a lot of the generic test set functions applicable to general analogue transceivers is either missing or hidden away, however the good news is that there are plenty of test sets about as AMPS and 2G networks have been replaced, but knowing the right units to go for is a bit of a minefield. I also use an Anritsu MT8802A which is more modern than the 2955 with an LCD panel, but these were predominently designed for cellular use, so you have to bypass the first menu when first boot it up. They are quite plentiful on eBay. Option 7 gets you a spectrum analyser integrated into it. On the downside, there are reports of the caps drying out in them. i re-capped mine a couple of months back after I was seeing intermittent faults, it's as good as new now, but it took me a day and a half to do it.Sorry, I made a lot of assumptions there, tell us more about the application.Edit: some examples of test sets...http://www.ebay.com/itm/351305840266http://www.ebay.com/itm/ANRITSU-MT8802A-with-SPECTRUM-ANALYZER-Option-/201275999257The 2955 has a rudimentary scope built in, but it's really only any good for audio work, but that may well be all you need.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: February 04, 2015, 11:44:33 pm
content: Are you sure your best choice is a scope? I spent many years in VHF/UHF mobile radio systems yet only needed a 50 MHz scope.200 MHz scopes such as the Rigol 2000 series are fair value, although an RF millivolt meter, basic RF probe, or perhaps a spectrum analyser may be more suitable for RF repair work.

author: smiffy68
author_rank: Newbie
timestamp: February 05, 2015, 04:46:25 pm
content: Howardlong, your assumptions are pretty darn right.I had looked at comms test sets, but new prices busted the budget big time. I was considering a new 'scope anyway to gain screen size, connectivity and reduce the vast amount of bench space the Hameg seems to take up, so the logic was to get something that would handle carrier freq at the same time.I have to confess I'd not considered S/H test set, but I must admit money spent on a Marconi would also tidy the bench up a bit as well! Sometimes its just having a recommendation and a model number to search for.Thanks chaps, I'll go back to looking at test sets.