Dear collegues,
found an old test receiver from Rohde & Schwarz, ESV 342.4020.53, in the store room of our lab. The unit is more than 20 years old, maybe even 30. Last calibration has been 10/99. The person who bought and used it retired approx. 15 years ago. At least this was told to me from the oldest employee of the group that is driving the lab. Back in the time when the unit was bought we used to develop our own measurement systems, including a wireless measurement data transmission system for car testing on test tracks. Today such things are simply covered up by wifi, but in these days you had to develop it by yourself.
After towing it to my desk, this guy seems to have more than 20 Kg, I switched it on and nothing happened. I found a melted fuse at the backside and exchanged it, but the new fuse also melted immediately. I opened up the power supply and found a big 10000uF capacitor (see 1st picture) with a shortcut inside (resistance approx. 150mOhm). Most likely dried out? Anyway, I exchanged it with two parallel 4700uF capacitors I found in one of my boxes and that fixed the problem.
The unit is now back in life. The last picture shows a test with a 200MHz carrier frequency modulated with a 1kHz signal. The measured signal strength was a little bit smaller, less than 1 dBuV, than the nominal transmitted strength of -6dBm resp. 100.99 dBuV. But I don't know how precise the transmitter really is, I used a tinySA as transmitter for the test, and how big the losses of cable, 50cm of RG142 should be neglectable, and the adapter from N-type / SMA are. For me the unit seems to work fine.
The Tek 2465B on top of the ESV shows the demodulated signal delivered by an output port on the backside of the test receiver.
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