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Author Topic: Reducing Screwdriver Antenna Brush Noise  (Read 571 times)
N3MG
Member

Posts: 27




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« on: May 28, 2002, 12:07:50 AM »

Any tips to reduce/eliminate the brush noise generated by HF screwdriver antennas?  I have grown use to it, but it sure would be nice to squelch it further.

I have a hard time believing that there are hams that actually grossly tune their screwdrivers by maximizing their received audio.  Are they listening to the hash or an actual intelligible signal (i.e. QSO)  as the motor turns?  If they are listening to the motor hash, I would agree you could grossly tune the antenna, but not by listening the normal audible band/atmospheric noise level.

I have ferrite beads on the motor leads at the antenna base and again at the screwdriver memory unit.  I am of the opinion the beads are to keep R.F. out of the screwdriver motor so that when you transmit, the motor doesn't rotate and disturb your match.  I imagine they might also help to keep the control line from acting like an antenna, and re-radiating the transients from the sparks generated by the brushes when the motor is energized.
 
I thought I came across someone mentioning the use of a metal oxide varistors across the motor leads in the antenna base.  Anyone try or heard of this and does it help?

Something tells me this is just one of those "just deal with it" kind of issues with screwdriver antennas.  At least when you think about it, you have a significant R.F. noise generating device inside the actual antenna.
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W5QRQ
Member

Posts: 5




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« Reply #1 on: May 28, 2002, 10:04:17 AM »

It sounds like you have a TarHeel antenna.  I had one too and it was very noisy.  After a lot of problems I sold the antenna.  I was never able to eliminate the noise problem.  The problem appeared to be with type of motor.

I did buy a HiQ antenna at Dayton and there is no motor noise. I can easily tune the antenna.  Charlie at HiQ had some very negative things to say about the TarHeel antenna.  I recommend that you switch to a HiQ.
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