[TowerTalk] Slow Attenuation of Incoming Signal

[Kelly Johnson]

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.  I've never heard it do this on
any band except 40m which leads me to believe it is my 40m antenna,
but I'm not sure about that.  I run a common feedline all the way up
the tower to a remote switchbox which switches between my SteppIR and
my 2 element 40m yagi.  If it's limited to 40m then it's either in my
rig OR between the switchbox and the 40m yagi.

Anyone have an idea?