I was asked to post the following info on rfi@contesting.com which I had
also posted earlier today on the topband@contesting.com, so here it is.
Within the last few months I noticed a raspy signal on 1.824 Mhz 24 hours a
day, 7 days a week. My 3 pennant RX antennas indicated the noise was
coming from a heading of approximately 135 degrees, and a large portable
shielded loop placed in my yard indicated a signal heading of 124 degrees
(reasonably close agreement).
I then set out on foot using a portable general coverage receiver and a
shielded loop, and tracked the problem down to a neighbors plasma TV set
that generated RFI regardless if it was on or off (signal first tracked
down to the power companies feed on the side of the neighbors house). The
RFI completely disappeared when the TV power cord was unplugged. Using
Google Earth the neighbors house is located approximately 350 feet from my
Pennants at a heading of 122 degrees (this house is not next door to my
house, and it's actually located on an adjacent street to mine).
Yesterday my first attempt at eliminating the RFI turned out to be very
rewarding. I constructed a simple power cord RF choke for the TV using 14
turns of a power cord on a 2.4" OD Fair-Rite #31 mix toroid core (based on
the K9YC hams guide to RFI document). The RFI at the neighbors house is
considerably reduced using the choke on the TV power cord, and the RFI at
my house appears nearly if not entirely gone. I will try adding another
choke in line with the first choke to see if additional reduction of RFI at
my neighbors home can be achieved, but I certainly can live with the
results of the single choke. I will also purchase and try a commercial two
stage power line filter on the neighbors TV to see how it compares with the
simple toroid choke approach.
I tried to document the problem and cure in a video I've posted on
youtube. If interested the youtube link is :
http://www.youtube.com/watch?v=mhJYCxJtFv0&feature=youtu.be
73,
Don (wd8dsb)
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