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@contesting.com> On Behalf Of Jim Brown
Sent: Thursday, October 19, 2023 5:13 PM
To: Rfi List <rfi@contesting.com>
Cc: rfi@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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