[VHFcontesting] Interstation Interference Question

[Steve Kavanagh]

Here's a question for some of you more experienced multi-ops.  At our recent CQ WW VHF Contest operation in FN05 we had some interference from the 6m transmitter into the 2m receiver.  It wasn't totally prohibitive but it was annoying at times...we had to stop transmitting on 6m while attempting EME contacts on 2m, for example.  The setup and tear-down were done in a great hurry this year, so we had no time to investigate properly.  I'd like your suggestions as to the most likely route by which the interference was getting in and how to fix it.

The 2m station was as follows: Elecraft K2 - DEMI transverter - DCI bandpass filter - TE1452G amp - Bird43 - antenna.
The 6m station was as follows: Kenwood TS-2000 - TE0552G amp - Bird 4304 - antenna.

The two antennas were around 30 ft apart and at the same height.

My first guess is that there is some transmitted noise at 144 MHz from the 6m rig/amp which got into the 2m antenna.  That could be eliminated by a low pass filter or stub on the 6m output.  Are there other possibilities I should consider before we try this again?  The 6m amp was run from a switching power supply, which makes me wonder a bit.  Radiation from the 6m amp power cables or ingress into the 2m station somewhere after the DCI filter (or on power lines) might be other possibilities.

What do you think?

73,
Steve VE3SMA