|481THz signal (top line) at 4.6km over the horizon tonight|
When I got home I checked the frequency to make absolutely sure that this was my carrier, which it was beyond any doubt. The signal was totally inaudible in the headphones and there was no sign whatsoever of the red beam in the sky. The most probable propagation was by scatter off dust particles in the atmosphere.
This was MUCH harder than I expected: I honestly expected to hear quite reasonable signals by ear, but as the plot shows, the signal was only just copyable in 84mHz. When I received my signal NLOS last year at 3.5km on a different path signals were 10dB over noise in a wider bandwidth on QRSS3.
At the moment I am still aiming the TX and RX as low as possible on the horizon, but I need to try greater elevations to see if this gives better to worse results over this sort of distance.
Another 6-10dB ERP from the Phlatlight LEDs (still to be fired up) would certainly help.