----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <topband@contesting.com>
Sent: Tuesday, January 31, 2012 11:51 AM
Subject: Re: Topband: Beverages Noise
On 1/30/2012 5:33 PM, Silvio M. Martín LW9EOC wrote:
> As I can remove noise entering through the ground? and how to isolate the
> shield?
A common mode choke, made by winding many turns of the coax around a
ferrite core, would help. The best core to use is Fair-Rite mix #31,
and you want at least 14 turns through a 2.4-inch outer diameter toroid
for 160M. 7-9 turns through a big one-inch inner diameter clamp-on will
work.
** A good feedline only ground rod that is completely isolated from the
Beverage transformers antenna winding ground rod by 5-10 meters should be
the first step.
ON4UN's latest revisions go thru this in detail.
The ferrite is useful for minimizing any common mode that remains.
Carl
KM1H
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
|