[RFI] 20 Meter Interference

K9MA k9ma at sdellington.us
Tue Feb 23 20:46:21 EST 2021

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 

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?


Scott K9MA

Scott  K9MA

k9ma at sdellington.us

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