630m WSPR

Cliff, N5CEY, has been listening to 630m WSPR stations over the past few days and has been consistently picking up three or four stations a night with his antenna system. I thought I would try the same using just the mini-whip antenna and the SDRplay receiver. The mini-whip has been fairly decent on the lower bands. I cranked up HDSDR and when I tuned to the WSPR frequency of 474.2 kHz and found a huge amount of inter-modulation products from local broadcast stations. I tried lowering the gain but they didn’t go away. Looks like I will need a low pass filter or an attenuator.

I then switched to using the SDRuno software that goes along with the SDRplay. It has some filtering features that I thought would be useful to try. The waterfall looked a lot quieter with this software for some reason and after piping the output to WSJT-X I was able to decode 630m WSPR spots from three stations overnight. This compares favorable to what N5CEY saw over the same period.

I will be playing with this some more to see if I can further optimize the receive.

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