Data Net 80m Experiments
On Tuesdays we often have a data net on 10m at 28.118MHz centre frequency, which was initially chosen so that we could mess about with a low risk of bothering other people. Although 10m can carry a long way in sunspot maxima via skip, it doesn’t usually propagate far at a minimum. This makes things difficult for people outside the immediate Glastonbury area
Martin G5FM and Richard G7LEE tried moving the net down to 80m. The RSGB lists 3.58 to 3.59 as a slot for 500Hz wide modes, we were using Olivia 16/500, so we moved to 3.58295MHz centre frequency. We achieved similar results to on 10m at a 20dB SNR using 10W. The wider reach became apparent however as we saw other QSOs pass - G5FM observed one station in Thessaloniki in Greece, and G7LEE answered Marc DG9BFE’s CQ on 3.5844 - Marc was in Emden in north-west Germany
One of the ideas was to try and widen the net to a SW wide net, using NVIS as we did with Blue Ham 1 The critical frequency falls at night, so 80m is not a bad choice for an evening net, however, skip will greatly increase QRM on 80m at the 9pm slot. Worth experimenting with, but we need to be mindful of other QSOs at this time because of the wide skip catchment area. At the moment we have no data about NVIS at this frequency, we need other users from beyond groundwave reach.
proposed modes/frequency selection
Olivia 16/500: 3.584 MHz or move up
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See also Witveliet et al, Near Vertical Incidence Skywave Propagation: Elevation Angles and Optimum Antenna Height for Horizontal Dipole Antennas in Antennas and Propagation Magazine, IEEE , vol.57, no.1, pp.129-146, Feb. 2015 10.1109/MAP.2015.2397071 ↩