Check for missing/bad RF by pass caps on the audio leads to the mike, and
maybe on the push to talk leads. Place these right at the connector inside
the radio, and use 0.1 mf disc ceramics as a start. Might try some ferrite
beads there as well.
In some TT production runs slight rearrangement of wiring could lead to hyper
sensitivity to RF, if other conditions of bypassing are not optimum. I
presume you have rig bonded with braid or copper strap to a common point for
other equipment cases, and the ground side of the antenna feed, but are you
feeding coax in the shack or ladder line? Check all coax jumper shields, I
have had those break inside coax connectors and play havoc like you describe
on my Scout.
(RF in audio). Sometimes, a design uses a lower cost cap, and if it was say a
0.01 mf disc, then there should be added a 0.1 mf in parallel with it to
common, with zero lead length if possible. How far is your antenna from your
rig? Are you on an upper floor of the house, or at ground level with the
shack?
Hope these points help,
Stuart K5KVH
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