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Re: [RFI] RFI LG Refrig Corcom filter and #31 core

To: Rfi List <rfi@contesting.com>
Subject: Re: [RFI] RFI LG Refrig Corcom filter and #31 core
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Wed, 29 Sep 2021 15:03:04 -0700
List-post: <mailto:rfi@contesting.com>
Thanks Don. How is the Corcom installed? For it to work well, it needs a VERY short bond to the chassis of the fridge. I would put the choke on the line side of the filter.

On what bands was there noise?

About the choke -- in doing the lab work for the 2018 Cookbook, I learned that turns wound around the core that are out of order within can cancel, reducing the effectiveness of the choke. Winding in order is relatively easy with toroids, but can be very tricky with clamp-ons.

73, Jim

On 9/29/2021 1:32 PM, Don Kirk wrote:
Hi Jim,

Once again the toroid core choke did not eliminate the RFI on its own. We tried the K9YC toroid choke by itself and it did not eliminate the RFI, we tried the corcom filter by itself and it did not eliminate the RFI.  It was only when we used both filters in series that Mike reported the RFI was gone.  I also tried the toroid choke before and then after the corcom filter with identical results on Mike’s RFI.

This is not the first time that I have had to use both filters to eliminate RFI.  The first time was on my wife’s treadmill.  It really is an interesting phenomena.  I suspect we would notice some components of the RFI disappear if looking at it with my SDR receiver or spectrum analyzer when using each filter on its own, but the bottom line is that both filters were required for Mike ti noice the RFI disappear.

Just FYI,

Don wd8dsb

On Wed, Sep 29, 2021 at 3:50 PM Jim Brown <jim@audiosystemsgroup.com <mailto:jim@audiosystemsgroup.com>> wrote:

    On 9/29/2021 12:10 PM, Mike Wetzel wrote:
     > My neighbor's LG refrigerator is radiating RFI on 28MHz and Don
    (WD8DSB)
     > temporarily hooked up a Corcom filter and a cord wrapped around a #31
     > torroid core that eliminated the interference.

    I'd bet that the turns around the toroid were doing all the work. Noise
    is most often on the green wire, which is a chassis-to=chassis
    connection on the filter.

    73, Jim K9YC
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