[Premium-Rx] removing strong nearfield signals

[Fred Munzenmayer]

A technique that may be usefull is phase cancellation. A strong undesired signal, (or local noise), from an antenna intended to favor it is combined with the main antenna. When the phase is adjusted to be exactly 180 degrees
opposite and exactly the same amplitude as the same signal on the main antenna, cancellation occurs. Two commercial units have been produced by JPS and MFJ for HF, and I recall seeing a similar VHF unit but forget the manufacturer's name.

Excellant results can be obtained with attention to the sense antenna to minimumize the desired signal. I constructed a passive unit some years ago that was published in the 
"Interference Handbook" by William Nelson. The two mentioned commercial units use simple amplification. 

The results are dependant on the undesired signal not varying in strength or phase, which would be the situation with a local broadcast station. 

I have been using a JPS unit in my truck to reduce ignition noise for my HF amateur installation. 
     

Fred   k2dx
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