Is this a pump which circulates hot water from a remote source? Something
tells that pump to kick on periodically, like a temperature sensor. I would
focus on that control circuit more so than the power lines. For instance,
Imagine there are long thermocouple wires which carry microvolts acting as
antennas and picking up RFI which confuses the control.
Good luck,
Joe K1VW
> On Dec 21, 2025, at 7:59 PM, Steve Muenich <srmuenich@gmail.com> wrote:
>
> Sure sounds like a weird one.
> Maybe try a temporary alternative power cord to a different power
> source/outlet.
>
> Steve, NA5C
>
>
> Sent from my mobile device
>
>> On Dec 21, 2025, at 6:14 PM, Dave (NK7Z) <dave@nk7z.net> wrote:
>>
>> Hello RFI group,
>>
>> I have an RFI case I am working on right now, that has stumped me
>> completely...
>>
>> A fellow Amateur has an Laing under sink recirculation pump model
>> ACT-303-BTW. Every time he transmits, the pump kicks in. The following
>> steps have been tried.
>>
>> 1. A Pile of clamp on ferrites have been added to the short power cord,
>> maybe 5 of them. No room yet to wind on an FT250-31, but that may be next.
>>
>> 2. The water piles have been connected to ground, using a car jumper cable.
>> The person who put this on tells me he used the ground on a outlet... Yes,
>> we will test differently with a real ground at some point soon.
>>
>> 3. He has reduced power to 50 watts and the pump still kicks in.
>>
>> 4. He has wrapped the pump in foil, and grounded the foil. Again, I am
>> sure via the outlet ground.
>>
>> 5. His dipole, which is close to the home, has a quality Balun Design choke
>> on it at the feedpoint.
>>
>> 6. The coax has been rerouted to as far as possible from the device as
>> possible, running on the ground as a test.
>>
>> The device is an older one, and sits under the sink. The ham is not sure if
>> his cold water pipes are at actual ground.
>>
>> I intend to do the following:
>>
>> 1. Use a real ground, if needed to ground the cold water pipes to the
>> service ground then bond to the pipes at the pump.
>>
>> 2. Replace the power cord with a longer version, and wrap 12 turns of AC
>> line cord in an FT240-31, and/or add an external RF filter to the AC line.
>>
>> 3. Reduce power further to try and pin down where the RF is getting in,
>> pipes, or power line by isolation.
>>
>> Purchase a good RF filter for the AC line. Can someone suggest an OTS one I
>> can recommend? He operates 80-10 Meters...
>>
>> Any other ideas?????
>>
>> 73, and thanks,
>> Dave (NK7Z)
>> https://www.nk7z.net
>> ARRL Volunteer Examiner
>> ARRL Technical Specialist, RFI
>> ARRL Asst. Director, NW Division, Technical Resources
>>
>> Random Quote of the day:
>> We are dominated by the relatively small number of persons who understand
>> the mental processes and social patterns of the masses. It is they who pull
>> the wires which control the public mind.
>> Edward Bernays
>>
>>
>>
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>
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