[1000mp] Inrad roofing mod to Mark V

[Pete Smith]

I'm running into a problem with my Mark 5 (200W version) which may have 
come up on the list before, but without a search mechanism on qth.net I 
haven't been able to find it.

Operating in the 160 meter contest this weekend with a receiving antenna on 
the RX IN antenna jack, I am experiencing quite low gain on that antenna. 
Where before, signal levels were approximately the same (after 
preamplification) as on my transmit antenna, now they are down ~15-20 
dB.  Moreover, I have discovered that if I press the front panel switch to 
listen on my transmit antenna, receiving on that antenna is also down 
considerably.  I can be confident of this because I know what my local 
noise level is typically.

Now here's the ugly part.  If I press the footswitch momentarily, switching 
to transmit and back to receive, listening on the transmit antenna, the 
signal level is restored.  As long as I do not again press the RX ANT 
switch, it stays up, even through multiple transmissions.  But as soon as I 
switch to the receive antenna again, the loss of received signal 
reappears.  If I cycle the footswitch, the level comes back up.

Cycling the footswitch while listening on the receive antenna does not seem 
to change the level of received signals on that antenna.  As I said, my 
impression is that receiving on that antenna is noticeably down from 
previous experience.  Powering down the preamplifier produces the expected 
loss of gain, so it appears to be working normally.

It looks to me as if I am experiencing a loss of signal in the relay which 
routes the signal to the receiver from the transmit antenna or from the 
receive antenna.  Is this a known problem?  How difficult is the relay to 
replace?

73, Pete N4ZR