Here is a quick followup regarding the RFI at W9RE on 10 meters that we
tracked down to his neighbors refrigerator a few weeks ago. We previously
were able to eliminate the RFI using a commercial power line filter in line
with a choke based on Jims (K9YC) design in which 12 turns of the power
cord were wound on an FT240-31 toroid core. While this combination worked,
we were looking for a plug and play commercial power line filter to replace
the Delta Electronics or Corcom filters that worked but were not plug and
play (they did not have built in outlet receptacles, etc.).
Mike purchased an APC C2 power line filter that had 2 built in outlets as
well as built in RFI/EMI filtering with a spec of 50dB from 100 kHz to 10
MHz (can't find the specs above 10 MHz or detailed specs regarding
differential mode versus common mode suppression).
Mike then wound 4 turns of the APC C2 power cord on an FT240-31 toroid core
based on recommendations from Jim (K9YC) for use on 10 meters.
Mike then gave the APC C2 filter with toroid core on the power cord as
mentioned above to his neighbor, and today Mikes neighbor tested this new
filter combination on his refrigerator while Mike listened to 10 meters
from his shack, and the new filter combination successfully eliminates the
RFI on 10 meters that Mike was encountering from his neighbors refrigerator.
The APC C2 filter is built like a tank (weighs approximately 2 pounds), and
we have no idea what the filter circuit inside it really is, but we are
satisfied with the results and the neighbor appears happy using this plug
and play system.
Just FYI,
Don (wd8dsb)
On Wed, Sep 29, 2021 at 7:41 PM Don Kirk <wd8dsb@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@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@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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>> > <http://lists.contesting.com/mailman/listinfo/rfi>
>> >
>>
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