RFI.1

RFI cures in an intercom.

I have worked on my intercom and now have it 95% improved but
not completely cured. I installed a ferrite bead on each of the lines from
the remote units where they connected to the main intercom circuit board.
This included the ground lines as well as the speaker and switch leads.
With these changes, if the intercom is playing from the am/fm source, I
hear absolutely nothing when my transmitter is keyed. Previously the entire
radio signal would have been muted and replaced by a loud buzz. If the
radio is not playing and the intercom is in standby (the usual mode) I
can hear a soft (but still annoying) buzz. I suspect the power line to
the intercom may be at fault but never got back to that. Early on I did
suspect the FM antenna but removing it made absolutely no difference.
Each system will be unique. My dipole is located within 2 feet of the FM
antenna so I could expect trouble. If the intercom was in the next house
I would expect absolutely no problem at all.