[CQ-Contest] radio interference

[Doug Grant]

NQ4I said:

> the operator on the 15m mult station hears the 20m
> station perfectly clear, no matter what frequency either station is tuned
> to...its some sort of if overload?

I bet the radios involved are the same kind (or at least have the same IF).
This is a real nuisance of a problem that is hard to track down and easy to
fix. I think it was at K1GQ's station that we first found this with a pair
of TS940s.

The problem is that the IF (70 MHz, for example, in  the FT1000 series) is
leaking out of the transmit radio somewhere, and finding its way into the
receive radio somehow. The "somewhere" can be the antenna connector, but
could be elsewhere. The solutions are:

1. Install generic low-pass TVI filters on the transmitter output. These
typically cut off between 30 and 50 MHz, and will knock any 70MHz IF leakage
at the radio output way down.

2. Make sure there aren't any other places for IF energy to leak out (or
in). Brute-force AC line filters will help here - either the packaged types,
or a whole bunch of ferrite on the power cord.

73, and Merry Christmas to all,

Doug K1DG