Tropospheric ducting is a type of radio propagation that tends to happen during periods of stable, anticyclonic weather. In this propagation method, when the signal encounters a rise in temperature in the atmosphere instead of the normal decrease (known as a temperature inversion), the higher refractive index of the atmosphere there will cause the signal to be bent. This is shown in the graph below, for the amateur radio bands from 1ber that for constant aperture, antenna gain goes up by 20 log f2f1 at each end of the circuit. I dont have to look far to find a masthead pre-amp at gm4fvm. It gets harder to apply such a simple set-up to a transmitreceive system like in a radio amateurs station. 12-18 the whole volume is 200 pages of interesting stuff on tropo- and ionoscatter report of jtac on radio transmission by ionospheric and tropospheric scatter, proc. Yeh, simple methods for designing troposcatter circuits, ire transactions on communications systems, september 1960, p. I was portable for a couple of hours late afternoon and worked 62 stations on fm. Military handbook, facility design for tropospheric scatter (transhorizon microwave system design). Propagation prediction software for ham radio category is a curation of 30 web resources on , beamfinder, hf propagation app for windows, wsprnet. Tv dx and fm dx is the active search for distant radio or television stations received during unusual atmospheric conditions. The term dx is an old telegraphic term meaning long distance. Vhfuhf television and radio signals are normally limited to a maximum deep fringe reception service area of approximately 40100 miles (64161 km) in areas where the broadcast spectrum is congested. Tropospheric scatter is the most common form of tropospheric enhancement. Tropo-scatter is always present to some degree just about everywhere.