[Elecraft] KX1 temporally deaf

[John Young]

This weekend I ran some test at a portable site our club will use to 
demo ham radio to about 50 youths.

We set up a Kenwood TS430, tuner and  20 meter dipole running on AC 
power.  I setup my KX1 with a
33 foot vertical with 33 foot counterpoise on the ground.  A third 
operator ran a DC-40 with a random wire
on the ground.

When I set up the KX1 I was copying a station in the MIQP near 7040.  
Before I could call him I heard
a very load station on 7040 with lots of signal while key up.  It was 
the DC-40.  After a short QSO, short in both
time and distance, I walked away from the rig for a few minutes.  When I 
returned the KX1 had no audio
out.
 
I tried 3 sets of earphones and also confirmed the phones were working 
with another source.  The KX1
didn't even have sidetone.  I assumed I had a failure of the audio out 
stage and suspected damage when
the TS430 tuned up at 100w on 20.

I packed things up and headed home where I checked the schematic before 
opening the case.  All that is
common to sidetone and receive audio is the last audio IC and volume 
control.  The XG1 showed a normal
S meter reading with 1 and 50 microvolts.  With the cover off I started 
touching parts around the input to the
audio amp listening for hum.  I got hum at the input of the amp.  

S meter and hum called for connecting an antenna.  At first I was not 
hearing much but over about 30 minutes
the receiver seemed to have recovered and I was able to work Tampa from 
Jacksonville on 7026 with no problem.

I have been playing with electronics and radio for fun and profit for 
well over 40 years.  I don't like things that
'fix themselves.'  Anyone have any ideas what might have happened?  
Could a high RF level cause temporary
deafness?  Keep in mind, this is a KX1 that landed 9Y0X on 20 after only 
40 minutes. N6VX operating - I'll
never be that class DXer.

72 John
WA8KNE