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Old 24th May 2020, 9:15 pm   #1
Steve G4WCS
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Default Rohde & Schwarz comms tester SMDU

Ive offered to curate one of these for a local radio amateur so I can recommission it and teach myself how to use it for checking radios out.

http://eww.ko4bb.com/manuals/82.40.3..._Datasheet.pdf

Is anyone familiar with them . Ive found the instruction sheet above and its a full set of circuits with it. Its spec says 0.14-525 Mhz, Ive started by unseizing and lubricating the drive gearing on the sig gen drum, and its appearing to work, triggering the counter on all the ranges except the 0.14-50 Mhz range. Ive taken the range switch off to switch solvent the switches as they were a bit gummy. Not put it back together yet but been looking at the circuits and the oscillator section doesnt have a 0.14-50 Mhz oscillator in it.
So I guess the exam question is does it have a 0.14-50Mhz range on the sig gen and if so how is it generated if I need to look elsewhere from the range switch pcb to look for a fault


https://youtu.be/Z0-QXiPySnU
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Old 24th May 2020, 11:16 pm   #2
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Default Re: Rohde & Schwarz comms tester SMDU

These things were sold with lots of sections optional. EG a firm whose business was fixing PMR VHF sets would not be interested in the coil sets for medium wave and HF.

One of the jobs is to find out just what you've got and what you haven't.

Look for R&S catalogues on the internet from its period and you should be able to fing the option codes the customer would have to specify, then look for a label on the beastie.

When sorted, you should find it a very useful box.


I bought a Gould one-box radio tester last year. Sig gen, power meter, modulation meter, audio source, distortion and SINAD meter, spectrum analyser. Synthesised and microprcessor controlled £100 at a rally up north. Came with its flight case as well.

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Old 26th May 2020, 6:00 pm   #3
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Default Re: Rohde & Schwarz comms tester SMDU

Cheers, Ive managed to find an instruction/service manual.Ill have to cope with the online bersion till I can access a printer.
It looks like the low range oscillator is a mixer job with a 240 mhz oscillator and the 10Mhz reference so I now know where to look if its more than dirty selection switches.

Happy days
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Old 26th May 2020, 9:24 pm   #4
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Default Re: Rohde & Schwarz comms tester SMDU

Spent an enjoyable few hours cleaning up the top section. Its come up very well. And it lives.
The lowest band IS working, but not triggering the counter when switched internally. Feeding the output back into the counter externally triggers it.
May warrant further investigation at some point but for now I can live with that. Its first job is to finish aligning an old ssb cb set so glad that band is working.

I can also take advantage of my freshly calibrated tcxo in my Yaesu ft-736 to check its 10MHz reference

The output control attenuator works, as does the am modulation, and the modulation meter is there or thereabouts. The channel synchroniser is working, and my scope seems to be good to a bit past 100Mhz, so Im happy, and the chap who gave it me is more than happy that its gone to a good home (its going to be open for club use anyway once I can drive it properly and we can socialise again) so smiles all round
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Last edited by Steve G4WCS; 26th May 2020 at 9:36 pm.
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Old 27th May 2020, 9:45 pm   #5
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Default Re: Rohde & Schwarz comms tester SMDU

Productive day. Cleaned up the power meter section and outer cases and did some antenna arranging,
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Old 14th Jul 2020, 9:22 pm   #6
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Default Re: Rohde & Schwarz comms tester SMDU

Its finished. A small knob was missing off the output level control. Had to go into work last week and picked up a morse trainer i’d made in the 90’s and fitted a scrap knob to the volume control. What are the chances of it being the right one. Partially learned how to drive it, the sig gen, counter, and power meter are working. Found an instruction manual online so looking forward to sussing the rest out
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Old 28th Oct 2020, 11:21 pm   #7
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Default Re: Rohde & Schwarz comms tester SMDU

Been having a play with the test set giving an old multimode cb a quick check. Am and fm receive ok, output power low on high band, probably needs realignment on the tx side, enjoy

https://youtu.be/4N4K1rYdbhg

https://youtu.be/5mehHOsyfrI

https://youtu.be/rjoAj4vLq3A
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Old 29th Oct 2020, 12:18 am   #8
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Default Re: Rohde & Schwarz comms tester SMDU

That's all sounding promising.

Is the counter malfunction an abrupt change on changing band or is it more of an uncertain and progressive degradation on some frequency? It might be a cracked DC block capacitor and you get stray coupling making it work only for higher frequencies.

I bought a Gould 'Stabilock 4031' a year ago up at the Moray club sale. My intent was to give it to the Kingdom ARS, but virus and loss of premises have put that off. This ia a later microprocessor controlled synthesised one-box-tester with spectrum analysis included. Seems to work. For transceiver testing , making up audio cables and PTT is the biggest part of the work. I even got it with a matching flight case.

David
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Old 29th Oct 2020, 11:10 am   #9
Steve G4WCS
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Default Re: Rohde & Schwarz comms tester SMDU

Quote:
Originally Posted by Radio Wrangler View Post
That's all sounding promising.

Is the counter malfunction an abrupt change on changing band or is it more of an uncertain and progressive degradation on some frequency? It might be a cracked DC block capacitor and you get stray coupling making it work only for higher frequencies.

I bought a Gould 'Stabilock 4031' a year ago up at the Moray club sale. My intent was to give it to the Kingdom ARS, but virus and loss of premises have put that off. This ia a later microprocessor controlled synthesised one-box-tester with spectrum analysis included. Seems to work. For transceiver testing , making up audio cables and PTT is the biggest part of the work. I even got it with a matching flight case.

David
morning David, yes its just when the counter is switched to read internally on the lowest band, so somewhere within that signal path lies an issue.

I do like the Gould Stabilocks, again they are a very good test set when working. I couldn't justify the purchase of one though unless it was earning its keep, maybe in a year or so when I have more time I could look into "rig doctoring" but having refurbished a few old radios, Im guessing its not easy to make a return on the hours invested
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