An experimental beacon on 144MHz has been deployed for evaluation. The beacon is designed to permit observation of aircraft enhancement propagation by way of a 200+s unmodulated carrier in each 300s cycle. Ident is by very slow Morse code. Necessary bandwidth (ITU-R SM.1138-3) is just under 5Hz, requiring 5Hz receiver bandwidth for ‘crisp’ decoding under weak signal conditions, but 1Hz receiver bandwidth is better for observing aircraft reflections.
There has been long running argument about whether such propagation paths are reflection from hot gasses behind the aircraft, or reflection from conducting skin on the aircraft. With increasing use of reinforced plastic skins, we may observe different response from similarly sized aircraft, depending on the skin, and these differences may be frequency dependent.
An interesting topic for study.
Details:
- frequency: 144.385MHz, 144.384Hz USB dial freq, 144.385MHZ dial frequency in CW mode on modern transceivers (accuracy should be within 200Hz);
- power: 20W EIRP (current details: https://vkspotter.com/?action=beacon-item&bid=355), ACT, horizontally polarised, antenna is 20m AGL;
- modulation: ~5 minute cycle uses A1 Morse modulation (OOK) QRSS1 (1s dits) callsign (VK1OD) followed by key down for the rest of the cycle;
- location is QF44op.
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