I'm sure every contester has been plagued by power line noise at one
time or another (or all the time !).
Using a combination of HF, VHF and UHF radios, I can usually isolate the
noise to 2 or 3 poles, but it's often hard to say which is the right
pole, and what on the pole is causing QRN.
At my old QTH, the power company QRN technician had an ultrasonic
detector that he could put on a hot stick (a telescoping, very insulated
pole) to pinpoint the source of the noise. With this device, he could
actually pinpoint the exact offending component. I was impressed, and
have always wanted one of my own.
I was quite excited to see the ultrasonic detector construction article
in April QST. It looks simple enough - I should have built one years ago !
If you decide to build one, here's a money-saving tip - Using the
promotion code FNDGFT, the shipping cost of the parabolic dish from
Edmund Scientific is reduced from $8.50 to $0.97.
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