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[TowerTalk] Power line filter question

To: towertalk reflector <towertalk@contesting.com>
Subject: [TowerTalk] Power line filter question
From: Grant Saviers <grants2@pacbell.net>
Date: Tue, 20 May 2014 08:23:30 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
With Field Day coming, I need to build some line filters for a multi station setup. The goal is two-fold, reduce hash from the Honda inverter-generator and reduce conducted noise from other stations. So the plan is a multi AC line filter assembly, one filter per main feed to each station and the common inputs to the gen.

From wayback experience, I know that a ferrite sleeve choke on the ground (green, grn/yel) made a big difference in conducted RFI, but IRRC such is now not ok per UL in the green wire for the usual plug in appliance. So those chokes are no longer inside UL approved line filters and the case is a common ground for both ends of the filter.

I have large (20a 120/240) Corcom and Sprague filters which look promising for common mode and differential mode filtering on line and neutral 120vac & will use one per station's AC power feed.

My question is where to put chokes on the ground wire - station side? gen side? both sides? Since there is no current unless a ground fault, it seems to me that a single FT-240-31 core with 8 to 10 turns of #14 THHN is plenty of inductance/resistance for 80-10m.

What would be the best grounding point for driven ground rods? Gen? Common of all filter cases (grn connection)?

Advice? (and reasoning pls)

Grant KZ1W
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