[Premium-Rx] removing strong nearfield signals

[Carcia, Frank A. HS]

back fill radiator

-----Original Message-----
From: John Perlick [mailto:p at mn.rr.com]
Sent: Friday, May 30, 2003 8:09 PM
To: Fred Munzenmayer; premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] removing strong nearfield signals


Sounds like the way we used to do radar ECCM at Raytheon....

----- Original Message ----- 
From: Fred Munzenmayer <mailto:premiumreceiver at comcast.net>  
To: premium-rx at ml.skirrow.org <mailto:premium-rx at ml.skirrow.org>  
Sent: Friday, May 30, 2003 7:01 PM
Subject: [Premium-Rx] removing strong nearfield signals

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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