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Old 19th Nov 2019, 9:06 pm   #2
Martin G7MRV
Heptode
 
Join Date: May 2008
Location: Selby, North Yorkshire, UK.
Posts: 949
Default Re: SARBE-5 (BE375) Very Odd Test Tesults!

Well, ive solved my problem, though im still not sure exactly what was going on!

Where I had tack-soldered my coax to the test-set to the unit, was at the point the antenna connects to the reed switch, via a 10pF capacitor. I was connected at the reed switch side - bypassing that cap. Putting a 10pF cap in series with my coax connection resolved the issue, and has allowed me to test and partially retune the radio. Theres no DC at that point, so I can only assume that the direct connection was influencing the receiver circuit somehow.

So now, I have a SARBE-5, with no Tx capability at all, and its AUX channel retuned to a more useful frequency for me to monitor, working to the spec of 20uV for a near fully quieting signal.

Sadly the same cant be said for the EMG channel, currently of course on 243MHz, which is somewhat deaf, needing nearly 200uV input for the same result. Im not very familiar with self-quenching super-regeneratives, so im not sure yet where to start on fixing this! I will probably move it a channel or two away from 243MHz though while I work it out!

Martin
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