[TowerTalk] Slow Attenuation of Incoming Signal

[Donald Chester]

>I've been noticing a strange phenomena that I'm hoping someone can help
>explain.
>
>I'll be sitting in front of the rig tuning the band and listening when all
>of a sudden the background noise level starts to drop and signals start to
>drop in strength.  After a couple of seconds signals are severely
>attenuated.  It's as if there is a variable attenuator in my coax line and
>someone turned it from 0dB to 50dB.  A single tap on the CW key brings it
>right back to normal once again.  It'll stay normal for minutes or even
>hours before doing it again.  A single "dit" from the key always brings it
>back to life.

Sounds  like the relay to me.  Relays sometimes do that, especially if they 
are not the type designed so that the contacts "wipe" across each other 
whenever the relay is energised.  It is probably due to oxidation.  Try 
cleaning the contacts with a burnishing tool or extra fine grade sandpaper 
(don't do this if the contacts are gold or silver plated).  Even a piece of 
printer paper makes a good contact burnishing tool.

If that clears up the problem, just make periodically cleaning the relay 
contacts part of your routine maintenance.

Othterwise, it might be some mechanical failure in the relay preventing the 
contacts from fully engaging in receive position.

On TX it may be the mechanical action of engaging and disengaging the relay 
contacts, or it could be the jolt of rf that is restoring continuity.

Don k4kyv

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