Sorry, I spoke too soon. Shortly after I sent the last message, the
interference returned, eve with the choke. It appears to be getting onto
the power wiring via the wall wart. I try a different one.
73,
Scott K9MA
On 2/26/2021 1:03 PM, K9MA wrote:
Half a dozen or so turns of the wire from the wall wart to the device
on a Radio Shack 2730104 "Snap-On" ferrite core completely eliminates
the interference. These cores generic. MFJ used to sell them, too.
According to the data sheet, 6 turns should be about 450 Ohms at 14 MHz.
73,
Scott K9MA
On 2/26/2021 12:04 PM, 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
--
Scott K9MA
k9ma@sdellington.us
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|
