[Icom] 765 output spike

[Floyd Sense]

In my recent query on this subject, I reported an output spike of 40-50
watts when hitting the PTT switch in SSB mode.  While troubleshooting a
separate problem, I discovered the cause of this one.  I access the audio
in/out lines on the rig via the ACC-1 connector on the rear panel, and I
feed the audio lines via mic cable to an interface box containing audio
isolation transformers (used for PSK31 operation).  It turns out that the
audio in and out lines at the ACC-1 connector are high impedance, and my
wiring in the transformer box was a bit of a mess, resulting in coupling
between the in/out audio lines and a bit of feedback.  Apparently during the
switch from receive to transmit, both are "on" for a short period and the
feedback was driving the audio-in line causing the spike.  This feedback was
occuring without a speaker, earphones, or microphone attached to the rig.

Redressing the lead lengths for the transformers reduced this coupling and
completely eliminated the switching spike.  I now see no trace of output
when the PTT line is activated without any audio drive.

K8AC