2018-12-28 Serious tropospheric ducting over Christmas
Normally, radio signals travel in a straight line and refraction in the ionosphere only happens on relatively low frequencies (below 30 MHz). Signals in the 2 meter band (144-146 MHz) don't get refracted in the ionosphere, they just leave earth. But in certain weather conditions with stable high-pressure areas layers can form that reflect these signals back to earth or create ducts in the air where the radio signals travel along the surface for much bigger distances than normal. For Christmas 2018 there was some troposperic ducting predicted on William Hepburn's Worldwide Tropospheric Ducting Forecast. This site forecasts ducting areas based on predicted weather patterns. To see the actual distances seen in radio contacts I check VHF propagation map based on APRS reception which uses input from APRS messages with location data received at other sites to find long distance contacts. During the Christmas festivities I checked that site from time to time and saw the big distance signal reports mostly over France, slowly creeping North. So on 25, 26, 27 and 28 December I ran the radio when possible on 2 meter FT8 and got some new distance records and some new gridsquares in the log. New distance record: 639 kilometer to G4RRA. Several other new calls in the log, some new gridsquares. When visiting the qrz pages of those calls I usually see serious setups with directional antennas so they all do the hard work transmitting in my direction and decoding my signal. This is all still with the 'simple' vertical for 2m/70cm: a Diamond X-300N on the roof. I wonder what I can do on a good day with a directional antenna and a rotor.