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Presented here, is a simple, but effective tool to assist
in location of RFI sources that frequently plague ham radio operators.
I live in a rural area that has very old power lines,
and frequently suffer from noise problems. Using this antenna, in
conjunction with my Ultrasonic Power Line Arc Detector, helps to pinpoint
troublesome RFI sources. My power company has been very responsive to
fixing problems, especially when I can help them identify the troublesome
poles.
This Project is based upon an article in the May 2007
QST Magazine (Pg 28) by James Hansen, W1TRC. It is designed for use on
135 MHz aircraft frequencies, since noise sources are easier to detect on
AM. James has also written an excellent article on an Ultrasonic Power Line
Arc Detector, which I have also built, and is described Here.....
When connected to your VHF Mobile rig (I use a Yaesu
FT-7800R), you have very useful portable RFI detection tool. I use the
antenna’s forward gain and directivity, to triangulate the RFI. After
getting close to the source, the very deep null off the back of the antenna,
is used to isolate the problem pole.
The elements are very flexible, making the antenna very
easy to get in and out of the car door. The elements just pop back into
shape after they come in contact with anything. When not in use, the antenna
breaks down into small pieces for easy storage. Very Cool!
The construction details are very straight forward, and
all of the components can be obtained for under $10 USD, at your local
hardware store. Consult James’s article in the May 2007 QST for
element and boom dimensions.
Good Luck, and happy hunting!
73’s Frank, K7SFN
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