[RFI] Filtering 220VAC

[nlsa at nlsa.com]

Dear Jim & all,

Thanks to everyone for their responses on- and off-net.  It has been unanimous that the neutral wire should not be excluded in add-on filters.

My question was an product of an RFI problem that I'm currently hunting and which has so far eluded capture.  It is coming from the Variable Frequency Drive for the elevation mechanism of my EME antenna (https://www.qrz.com/db/W9IP ).  When the elevation VFD is powered on (but not running) it raises my noise floor by about 0.6 dB (HFers, don't laugh).  I spent all day adding chokes and bypassing the 220VAC input, but recent posts tell me that I wound the common mode chokes improperly.  No perceptible noise is being emitted through the output of the VFD, its LAN connection, or other related control lines... just the AC power.  Tomorrow I will re-wind the chokes.

W9IP
-----Original Message-----
From: RFI <rfi-bounces+nlsa=nlsa.com at contesting.com> On Behalf Of Jim Brown
Sent: Thursday, October 19, 2023 5:13 PM
To: Rfi List <rfi at contesting.com>
Cc: rfi at contesting.com
Subject: Re: [RFI] Filtering 220VAC

On 10/19/2023 2:02 PM, David Eckhardt wrote:
> And further:  No more than 3 or 4 non-overlapping turns through the 
> toroidal core.

Turns should be wound sequentially around the core(s). Photographic examples and other details are on pages 22 and 23 of

http://k9yc.com/RFI-Ham.pdf

The filter of Fig 30 was added to the ARRL Handbook several years ago. 
Although we built it for the generators we use for county expeditions, it's universally applicable to HF.

73, Jim K9YC
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