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Re: Topband: Rotator Potentiometer shunt fed twr

To: topband@contesting.com
Subject: Re: Topband: Rotator Potentiometer shunt fed twr
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sun, 23 Aug 2020 14:04:05 -0700
List-post: <mailto:topband@contesting.com>
On 8/23/2020 12:39 PM, dj7ww@t-online.de wrote:
Bypass the rotor with thick ground lead from the rotating pipe mast to the
tower

Yes. This solves other issues.

 use ceramic bypass capacitors on the pot contacts and MOVs or low
voltage spark gaps to ground on all lines to the rotor and controller.

MOVs are a very bad idea, and I see no benefit from the caps.

Use screened rotor cable, with the screen grounded to the tower at top and
bottom.

I don't see the need for this.

If the rotator cable is laced to the tower (most prefer the inside of a tower leg) it will be at the same potential as the tower all the way along the height, thanks to capacitance between the cable(s) and the tower. Remember, this is RF, not DC, and the current we're talking about is antenna current, which is near a maximum at the base an minimum at the ends of the elements of the Yagi(s) that serve as top loading.

73, Jim K9YC


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