Interference patterns on 40m - comments sought

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Interference patterns on 40m - comments sought

I'd appreciate any comments or insights, and any similar observations, on the interference patterns I've seen on the 40 WSPR segment. My location is suburban Southampton on the south coast of England. I'm pretty sure this interference is not from within the house. I do live within 700 metres of an university with electronics, electrical engineering and biomedical departments. My receiver is a homebrew direct conversion with a single crystal filter front end, a development of the design of Gene Marcus W3PM at

An example from daytime 3 July is attached as a png image file. I've now set up a cron job to capture screen images at hourly intervals (except for glitches). I now have three days captured, pdf file of thumbnails attached, from 0546UTC on 7 July to 0630UTC on 10 July. You'll see the interference has moved to the night-time.

You'll see that I prefer the ZL1FZ palette, and I've the waterfall gain and zero adjusted to give a lightly speckled black background when the band was quiet.There were no adjustments to waterfall gain or zero during this period.

I look forward to your thoughts.

Gwyn G3ZIL