I have a problem that appears to be changing, but I could use some
help. The problem is RFI in the audio input (microphone input) when I
use my vertical antenna on 40 meters. Here is a rundown of what has
happened:
I have a 67-foot elevated vertical that I can use on 80 and 40, and it
works fine on CW. However, on SSB, both bands, there clearly is
feedback; there is no feedback on the other bands where I use a C3
yagi. Initially, the feedback was so bad that the rig would go into
oscillation, and I had to turn the amp to standby.
I recently purchased the new KSYN3A and decided to install it. I
replaced the K3 with my IC-730 backup, using the hand microphone that
came with the 730. The 730 did not have any RFI. I finished the
modification and returned the K3 as the operating rig. Now, the RFI on
40 seems to have diminished substantially or disappeared, but it still
happens on 75/80. However, it seems to be much less there as well. I
do not suspect that the KSYN3A had anything to do with this, but perhaps
I tightened connections better when I returned the rig to service. I
also redid some ground connections.
The microphone for the K3 is an Audio-Technica that works well
everywhere else. It has a long cord, though. I put a few toroids on
the cord near the microphone connector and that has possibly reduced RFI
a little, but it is still there.
Is there a possibility that a bypass capacitor is bad, or has someone
else had the problem and solved it externally to the K3? For instance,
has anyone found that a long string of ferrite beads has cured this problem?
Despite decades of operating, I am hardly a troubleshooting hotshot, and
I would appreciate guidance.
Thank you,
Jan, KX2A
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