[Towertalk] Ham-M RF in the shack

[GEORGE PRITCHARD]

I noticed distortion in my audio when I set the quad for vertical or circular polarization... horizontal was no problem. I discovered that the rotor cable (running vertically) was picking up RF and bringing it into the shack. Problem very noticable with the linear on. The cure: attach the rotor cable to the coax entrance service panel with a high quality military connector and ADD RF BYPASS CAPACITORS (.01UF 1KV) TO EACH LINE TO GROUND. Problem solved. It took me weeks to figure this out. The clue was: The rotor box control indicator would "modulate" the direction indicator about 30 degrees depending on the power level... with the box off. I just happen to see it while transmitting, and wondered how it could move with the box off! I then realized where the audio distortion was comming from. I previously saw the indicator moving with modulation, and thought it was a line regulation problem moving the indicator with the linear on. Very weird. Talk about barking up the wrong tree!
George AB2KC


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