[Elecraft] Intermittent RXsensitivity...

[Geoffrey Mackenzie-Kennedy]

Don W3FPR wrote


> Gerald,
>
> That certainly sounds like it might be hard to isolate.
> I may be wrong, but from the behavior it sounds like you have a relay with
> points that are not making good contact - when you put a bit of RF through
> it, it becomes OK for a while.  Please be aware that this is just
> speculation on my part.  You may have to work with it a lot to determine 
> if
> it is really fixed.  Intermittents are very difficult to troubleshoot.

 <snip>

> If you can induce the failure and then have it continue while you remove 
> the
> heat sink, you could also check the relay points with a continuity test
> between the pins.  Check the schematic key for the realy chart and the
> schematic itself for the appropriate relay points and pins.

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Gerald,

I agree with Don about a possible problem with relay contacts, I had a relay 
problem with my K2 some time ago which caused the receiver's sensitivity on 
40m to decrease but which could be restored by either changing the band from 
40m and back again, or transmitting a couple of dits. The cause of my 
problem was K1's contacts which switch in the 40m bandpass filter, 
specifically those of K1A.

With all due respect to Don, making a continuity test might fool you unless 
the relay contacts have failed and are not just 'dirty', because the current 
from a DMM etc when reading low ohms might be enough to 'clean' a dirty 
contact just as a little bit of RF would, but certainly worth trying and 
would expose a more severe problem.

If the problem is a 'dirty' contact sometimes the slightest vibration or 
movement of the rig / relay can 'cure' the problem - for a very short time.

Since I am obliged to QRT for a several hours, please let me know if you 
would like to hear more.

73,
Geoff
GM4ESD