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

[Don Kirk]

Hi Jim,

I forgot to answer your question about what bands the RFI was on.  Mike was
only experiencing noise on 10 meters, so I did not look at other bands.
Because we were dealing with 10 meters I also wondered if we should try #43
material in place of the #31 material on the common mode choke to see if
that would be beneficial, and you might share your thoughts on the use of
#43 material versus #31 material up on 10 meters for the common mode choke.

Thanks,
Don (wd8dsb)

On Wed, Sep 29, 2021 at 7:41 PM Don Kirk <wd8dsb at gmail.com> wrote:

> Hi Jim,
>
> For the records, we actually tried two different commercial filters on the
> fridge along with the common mode choke.  Both required the common mode
> choke in line with it to successfully eliminate the RFI at Mikes, and as
> mentioned the common mode choke alone was not adequate.  My common mode
> choke used the FT240-31 core with 14 turns and the turns are tightly wound
> one next to the other in proper order.
>
> The case of the commercial filters were not mounted directly to the case
> of the fridge, but the ground wire from the fridge power cord was connected
> to the case of the commercial line filter, and the case of the commercial
> filter then had a wire connected to it going out toward the wall outlet
> ground via the power cord, so the ground wire from the fridge was a
> continuous connection to the commercial filter case and then from the
> commercial filter case to toward outlet ground.  All power cords used were
> 3 wire (line, neutral, and ground).
>
> The two commercial filters we tried were the Delta Electronics model
> 20DRGG5 (which is mine) and an old Corcom filter F2212 (which is Mikes, and
> I can't find any documentation on the F2212 filter).  We pretty much had
> identical results regardless of which one of the 2 commercial filters we
> used in conjunction with or without the FT-240-31 choke.  Commercial filter
> alone was not adequate, FT-240-31 common mode choke alone was not adequate,
> but both in series work great.  This is the same situation with my
> treadmill, and I also don't have the case of the commercial filter mounted
> to the case of the treadmill.  Mounting filter case to the case/frame of a
> homeowners device starts getting very intrusive, and I won't take on that
> responsibility/liability.  As Mike mentioned we need to find something
> already packaged with incoming and outgoing outlets/power cords for use in
> someones home in order to avoid liability issues.
>
> Just FYI, and 73.
> Don (wd8dsb)
>
> On Wed, Sep 29, 2021 at 6:24 PM Jim Brown <jim at audiosystemsgroup.com>
> wrote:
>
>> 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 at audiosystemsgroup.com
>> > <mailto:jim at 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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