Topband: Common Mode

Arthur Delibert radio75a3 at
Mon Nov 12 18:02:01 EST 2018

David --

Suggest you take a look at the attached paper by Jim Brown.  I live in a fairly dense suburb where every house (including mine) has all the latest RF noise-makers.  Following Brown's suggestions, I've put large 31-material clamp-on ferrites on both ends of my receive antenna feedlines (and sometimes one in the middle), and it makes a very clear difference.

Art Delibert, KB3FJO

From: Topband <topband-bounces at> on behalf of Rodman, David <rodman at>
Sent: Tuesday, October 23, 2018 6:41 AM
To: topband at
Subject: Topband: Common Mode

I purchased some 7mm dia snap on cores for RG6 receive antenna coax.  I was wondering if anyone had any experience or suggestion as to how many one would place on each lead.  The feed lines are about 50% on the ground with grass growing over or buried 2-3".  The lengths vary from 300' to 750', depending on the antenna I am using for listening.  I was planning to place them inside the station.  I have nothing now and thought this would be acceptable versus removing connectors and placing beads?  Thank you.

David J Rodman MD
Assistant Clinical Professor
Department of Ophthalmology

Office 716-857-8654
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