Been there, done that....my culprit was a catv modem that also provides voip
phone service....I guess the fcc requires them to have a battery backup in them
so you can still use the phone in a power outage.....cable company swapped it
out, new one much quieter
Sent from my iPad
> On Feb 26, 2021, at 6:05 PM, r55stan@gmail.com wrote:
>
> Don't forget to also turn off any battery backup power, such as
> uninterruptable power supplies many of us use for computers, WiFi routers
> etc. The inverters in them and the devices they power will still be on. I
> once wasted a few hours searching for RFI that was still there after all of
> my circuit breakers were off. Since the breakers were off I first assumed it
> must be from a neighbor. It ended up being Ethernet on CAT5 cables in my own
> house, which was running on the backup power supply.
>
> Good luck hunting,
>
> Randy KQ6RS
>
> -----Original Message-----
> From: RFI <rfi-bounces+r55stan=gmail.com@contesting.com> On Behalf Of K9MA
> Sent: Friday, February 26, 2021 2:37 PM
> To: rfi@contesting.com
> Subject: Re: [RFI] Fwd: 20 Meter Interference
>
> Yes, I discovered it by running the radio on a battery and turning off
> circuit breakers.
>
> The culprit definitely was the wall wart. The cyclic pattern apparently was
> due to the device intermittently loading it.
>
> 73,
> Scott K9MA
>
>> On 2/26/2021 2:13 PM, Dave Cole wrote:
>> Did you discover this during a home power off test?
>>
>> 73, and thanks,
>> Dave (NK7Z)
>> https://www.nk7z.net
>> ARRL Volunteer Examiner
>> ARRL Technical Specialist, RFI
>> ARRL Asst. Director, NW Division, Technical Resources
>>
>>> On 2/26/21 10:04 AM, K9MA wrote:
>>> It turned out to be a wireless doorbell extender, right in the shack.
>>> Once again proving that one should check your own home first. I'm not
>>> sure if it's the wall wart or the device itself. It seems to have
>>> magically fixed itself after power cycling, but I'm sure it will be
>>> back.
>>>
>>> I suspect the 1.1 second interval between noise pulses is the polling
>>> period of the device, when it draws current from the wall wart. If a
>>> ferrite core on the power lead doesn't fix it, I'll just unplug it
>>> when operating. Who wants to be disturbed by the doorbell then, anyway?
>>>
>>> 73,
>>>
>>> Scott K9MA
>>>
>>>
>>>
>>> -------- Forwarded Message --------
>>> Subject: Re: [RFI] 20 Meter Interference
>>> Date: Tue, 23 Feb 2021 20:25:09 -0600
>>> From: K9MA <k9ma@sdellington.us>
>>> To: rfi@contesting.com
>>>
>>>
>>>
>>> The spectra images didn't come through, so here are the links:
>>>
>>> http://sdellington.us/hr/RFI/20m_K9MA.jpg
>>> <http://sdellington.us/hr/RFI/20m_K9MA.jpg>
>>>
>>> http://sdellington.us/hr/RFI/20m1_K9MA.jpg
>>> <http://sdellington.us/hr/RFI/20m1_K9MA.jpg>
>>>
>>> 73,
>>> Scott K9MA
>>>
>>>
>>>
>>> On 2/23/2021 7:46 PM, K9MA wrote:
>>>> I've recently started seeing this signal on 20 meters, probably
>>>> local, as it is present late at night when the band is dead. It is a
>>>> swept signal, typically starting at about 13.625, sweeping upward to
>>>> a sharp cutoff at about 14.125. The total sweep seems to be about
>>>> 500 kHz. The sweep slows down near the upper limit and seems to
>>>> dwell there. Sweep repeats about once per second. It seems to be
>>>> amplitude modulated during the sweep, so it shows up as a series of
>>>> pulses on the waterfall display. While the frequency range seems
>>>> fairly stable, it does move around a bit. I can't tell whether the
>>>> frequency change is systematic or random.
>>>>
>>>> In the attached images, the blue trace is the peak signal,
>>>> accumulated over many sweeps. The yellow one is the actual signal,
>>>> without averaging, which I caught near the upper end of the sweep.
>>>> The waterfall shows the pulsed modulation. Resolution bandwidth is
>>>> about 440 Hz.
>>>>
>>>> Any idea what this might be?
>>>>
>>>> 73,
>>>>
>>>> Scott K9MA
>>>>
>>>
>> _______________________________________________
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>
>
> --
> Scott K9MA
>
> k9ma@sdellington.us
>
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