WSPR Beacon on 10 Meters

In collaboration with The Case Amateur Radio Club of Case Western Reserve University, W8EDU, (see their side of the story here), students at the University of Michigan Amateur Radio Club assembled a raspberry pi + LPF WSPR beacon to be used on 10m. This setup transmits ~10dBm (10mW) through 3 RF switches, a few hundred feet of coax, and through a 10-40m trapped vertical antenna.

Temporary hacked-together RPi WSPR transmitter for trial-running initial tests.

Transmissions were successfully reported by multiple stations at on bands between 80m and 15m. Transmissions on 10m from W8UM to W8EDU have been unsuccessful so far, having tried the 10mW from the raspberry pi, as well as short-duration transmissions using 5W, 10W, and eventually 20W from the Kenwood. The high power transmission station has been shut off, but continues to operate in receive-only mode.

Initial results – transmitting from the RPi at <10mW for 24 hours on 11/19/2019
Initial results 2 – transmitting from the RPi at <10mW from 4PM ET to 10PM ET on 11/20/2019

W8UM has been able to hear W8EDU’s transmissions on 10m, using a SteppIR HF yagi antenna pointed at heading 116 degrees from north. Initial results are presented in the graph below: maps W8UM’s reception of W8EDU on 10mWSPR

It was observed that the raspberry pi transmitting WSPR idles on the frequency previously transmitted on, even after the transmission ends. This causes causing local interference that desensitizes our simultaneous signal reception. With the Raspberry pi rotating between 40m, 10m, 10m, 20m (in order), while the Kenwood alternates on TX, RX, TX, RX on 10m, we get alternating points of high and low signal levels that make the resulting data unusable.

Todo: think about why the transmit from W8UM -> W8EDU isn’t working, and rebuild the RPi beacon into a more permanent solution.

First Draft N9KIT, 11/23/2019 16:06 ET