[RFI] Interference from AC units

Hare, Ed W1RFI w1rfi at arrl.org
Thu Sep 8 06:26:00 PDT 2011

I'd imagine that if an FT-240 size core was used, that large core was selected to use multiple turns of wire.  I would hope so, anyway. :-)
Ed Hare, W1RFI
ARRL Laboratory Manager
225 Main St
Newington, CT 06111
Tel: 860-594-0318
Email: W1RFI at arrl.org


From: Jim Brown [mailto:jim at audiosystemsgroup.com]
Sent: Sun 8/28/2011 10:00 AM
To: rfi at contesting.com
Subject: Re: [RFI] Interference from AC units

On 8/26/2011 5:08 PM, Richard Battles wrote:
> i had the installer
> put ft-240-43 ferrite cores on the wires leaving the unit to the wall
> thermostat, outside unit, and what ever else.

That is VERY unlikely to have had any effect on RFI on the HF bands. It
MIGHT have had some small effect on 2M.  For ferrites to do anything at
HF, we must wind multiple turns around them.

In other words, if your system is RF-quiet, it was built that way.

73, Jim Brown K9YC
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RFI at contesting.com

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