[RFI] 20 Meter Interference

K9MA k9ma at sdellington.us
Tue Feb 23 21:25:09 EST 2021

The spectra images didn't come through, so here are the links:



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 at sdellington.us

More information about the RFI mailing list