Satgen153 Radio Amateur Experimenter Myth by GM4IHJ 1st March 1992 Radio Amateurs sometimes talk as if they are at the forefront of Radio developements, but this is a hangover from the shortwave work of the 1920s and 30s, and the SSB work of the late 40s . When questioned, hams say, there are no new fields to conquer. But one look at our present inability to understand HF ionospheric propagation, shows this is not true. RadCom still lingers in the dark ages with caveman drawings of ionospheres 3200 kms high, and while some propagation reports may mention non great circle propagation (NGC), it is clear that noticing the phenomenon is not coupled with any effort to understand it. How can we do better ? We can start by looking hard at what we are getting on RS12 Mode K, where the constant movement and consequent doppler shift of the satellite can tell us an enormous amount about the signal path. Eg consider G3IORs sub horizon contact at 1838ut on 17 Feb when RS12 was moving north up the Pacific, 1400 kms west of San Francisco. Using a 3 element beam Pat's azimuth was 350, but the calculated satellite great circle bearing was nearer 315 from Norwich. Earlier both Pat and I monitored RS12 near Japan ( GC bearing 30 to 45 ) but Pats antenna was near 350 azimuth for best results , and my doppler indicated angle on the bow of RS12 was similarly 40 degrees away from the expected GC path. So clearly non great circle propagation is rife. How can we learn more ? Answer - BY DOPPLER SHIFT CHECKS. 1. If we know RS12 closest approach zero doppler frequency on our receiver (measured on a pass near UK ) 2. We can measure doppler shift when RS12 is remote from us and get the angle on the satellites bow at which the signal departed the satellite PLEASE NOTE THAT THIS TEST DOES NOT NEED A 3 ELEMENT BEAM. NGC propagation affects all HF signals. both terrestrial and satellite. It is much more obvious on 50MHz where we all use beams but it is present down at 7MHz and even 1.8 MHz. It can make a tremendous difference to DX work , providing paths to distant DX when the ordinary Great Circle path is simply not open. Propagation studies are vital to our future progress . They are not done by committees or armchair Amsat groups. They are done by skilled operators and experimenters. This is what RSGB/ARRL/Amsat should be encouraging. Less blather . More Experiments. 73 de John GM4IHJ @ GB7SAN