[RFI] Array Solutions Filtermax III not making any difference on radio 2. What to check?

[Jim Brown]

On 10/27/2018 4:31 PM, Andy KU7T wrote:
> We go the mentioned filter at our contest station. We got S6+ Interference from the run to the multi station. If we switch the bandpass on the run from the band to bypass, the noise level does not change at all. The relays in the box switch and the band pass is working ( meaning switching to the wrong band quiets the receiver).

 From what band to what band?  Are you using a power amp on either 
station? How much antenna separation?  Does one face the other? Do you 
have serious common mode chokes at the feedpoint of every antenna?

> Is it possible the filter is working but not make any difference? Does that mean we just get RF from somewhere else and need to find it?  Any tips how?

Lots of things can cause interstation interference that bandpass filters 
won't fix. Bandpass filters between rig and amp do nothing for harmonics 
created by the amp. And bandpass filters do nothing if the other station 
is on the same band.  Also, passive intermod (mixing in some non-linear 
"thing") creates harmonics that nothing can filter -- you've got to find 
and kill the "thing."

73, Jim K9YC