Sorry Jim Of course simply passing a wire through a clamp on ferrite has
minimal effect. Even the Lennox instruction for their RFI kit showed winding
two turns around the ferrite bead. I imaginge they supplied the split bead
clamp on as a convenience for the installer. This allowed the installer to
place the bead without disconnecting one end of the wire. I wound multiple
turns around the doughnuts I installed.
Your articles have been invaluable Jim! A frequently referenced collection by
myself and many others I am sure.
Ed
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Jim Brown
Sent: Saturday, November 03, 2018 12:30 PM
To: rfi@contesting.com
Subject: Re: [RFI] RFI from furnace/air conditioning
Hi Ed,
Simply clamping a ferrite onto a wire carrying RF noise has little effect on it
on the HF bands. We must wind turns of the wire through the core. I wrote a
tutorial on this a few years ago for NCJ. It's on my website.
http://k9yc.com/KillingReceiveNoise.pdf
73, Jim K9YC
On 11/3/2018 5:39 AM, Ed wrote:
> I believe we have the same HVAC unit as you do and indeed found some
> unacceptable RFI coming from the unit. Lennox is actually aware of this and
> will provide a filter kit (ours was at no cost) consisting of an AAC line
> filter and a couple clamp on ferrites. Once installed this helped
> significantly but did not eliminate the problem. I added a couple more mix
> 31 doughnuts in place of their clamp-on's and also added one on the
> thermostat line at the thermostat and the problem seems to have been reduced
> to the point where my antennas do not see the noise.
>
> Contact your local installer and ask for the kit or contact Lennox directly.
>
> Ed - VE4EAR
>
> -----Original Message-----
> From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of D C _Mac_
> Macdonald
> Sent: Friday, November 02, 2018 6:05 PM
> To: RFI Group <rfi@contesting.com>
> Subject: [RFI] RFI from furnace/air conditioning
>
> I have fairly recently gotten back on the air after a few years off. This is
> AFTER I had to have our HVAC replaced. It is a Lennox SL280UH090V48B-03
> which is a variable BTU and variable speed fan system. Lots of trash,
> especially on 20 meter band. Does anyone here have experience with Lennox
> systems in general or my specific unit ?
>
> 73 de Mac, K2GKK/5
> (Since 30 Nov '53)
> Oklahoma City, OK
> USAF Retired 61-81
> FAA Retired 94-10
>
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