[RFI] BCB Intermodulation and HV transmission lines

[Ed Richardson]

I have been plagued by AM intermodulation products between 2 and 4 MHz. for several years. I have verified they are not generated in my receivers. Installed high pass and bandpass filters and this does not affect the level. I have knocked the -10 dBm AM signals levels down to -90 dBm at the RX antenna port.

With a handheld spectrum analyzer I have searched the neighborhood for the source and the only potential source I have come up with is a High Voltage transmission line that runs about 500m north of my tower. When directly under one of the 3 parallel lines, I can detect the intermod products. If I connect the telescopic antenna to transmission tower, the intermod product rises to a -40 dBm. The lines are probably 30m overhead.

We are about 5-8 km from the AM transmission sites of at least 5 broadcasters. 

The intermod is primarily 3rd order, 2F1+/- F2.

Has anyone else seen this before and if so, were you able to get it resolved?

Ed, VE4EAR