QSL on everything. Also, put a "common mode choke" in that feedline - may
two chokes, one at the entrance to your house and another out at the
antenna.
-----Original Message-----
From: RFI [mailto:rfi-bounces+lloydberg=tds.net@contesting.com] On Behalf Of
Dave Cole
Sent: Saturday, April 03, 2021 9:17 AM
To: rfi@contesting.com
Subject: Re: [RFI] Raspberry PI / Wall wart RFI
Do all three actions, look over Jim's papers, get a linear power supply, and
move your loop as far from anything as possible.
Many years ago, while vetting the use of a loop as a RX antenna, I did a few
tests moving the loop further and further from my home and watching the RFI
levels.
Unfortunately I did not document the process, however, the general gist of
the testing was to move the antenna far, far away from all noise sources,
which of course makes perfect sense. I was not aware at that time of just
how much RFI a home can generate... A lot!
I do remember setting the loop up in my kitchen, getting an S9, or higher
noise level, then moving the loop to the deck outside, and getting far less
RFI, something like S5, or S6, then moving the loop to the backyard, 60 feet
from any RFI sources, out in the middle of a grassy field, and getting an
S3, or S4 noise level... All using the same length of feedline.
That taught just how much RFI a home can generate, and that is worth it to
move antenna as far as possible from all structures.
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 4/3/21 6:03 AM, David Gottschalk wrote:
> Thanks Jim.
>
> Some others have also already suggested a linear power supply. I'll
> probably try that, but I'm strongly considering just moving my antenna
> much further away from my house, so I can spend less time trying to kill
RFI.
>
> On Fri, Apr 2, 2021 at 8:49 PM Jim Brown <jim@audiosystemsgroup.com>
wrote:
>
>> That's because it's a switch-mode power supply. What voltage and
>> current? Depending on that, it may be possible to re-purpose an old
>> linear wall wart. Also, study my tutorials on chasing and killing RFI.
>> They include specific advice on subbing the linear supply.
>>
>> Text: http://k9yc.com/KillingReceiveNoise.pdf
>> Slides: http://k9yc.com/KillingRXNoiseVisalia.pdf
>>
>> 73, Jim K9YC
>>
>> On 4/2/2021 5:15 PM, David Gottschalk wrote:
>>> I'm wondering if anyone has had success finding a wall wart for a
>> Raspberry
>>> Pi that doesn't make horrific RFI on HF (or really any switch mode
>>> power supply that isn't noisy!)
>>>
>>> I recently discovered the wall wart for my Raspberry PI (that is
>>> mounted outside in a water proof enclosure for my 4G internet) is
>>> making S7 level noise on 80m. Unfortunately, my 80m loop is currently
pretty close to it.
>>> When the PI is battery powered, or off, it's S4 noise level here
>>> (This is in the middle of the day). 60m also seems to be severely
>>> affected as
>> well.
>>>
>>> I found this on Amazon, but it seems like it's more of a AC line
>>> conditioner, but might be worth a shot. Any feedback would be
>>> greatly appreciated.
>>>
>>>
>> https://www.amazon.com/iPower-Supply-International-Travel-Adapters/dp
>> /B01GNNXP0Y?ref_=ast_sto_dp&th=1
>>>
>>> 73,
>>> David
>>> KN4ZKT
>>> _______________________________________________
>>> RFI mailing list
>>> RFI@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/rfi
>>>
>>
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