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« on: May 22, 2011, 09:32:25 PM »
So after gaining qualifications in radio propagation theory, more information:
UHF- will not ever bounce off the ionosphere. It will simply pass straight through.
The only waves that will 'bounce' (Really, they refract towards earth), are those in and below the HF bands. Even then, depending on weather, temperature, time of day and solar activity, some frequencies will not refract. HF is used for long-range comms for the reason that it will diffract over terrain, refract off the ionosphere, and reflect of the surface of earth. Attenuation of signals will occur but this is irrelevant. V/UHF are used for line of sight comms and is easier to use for that reason. Ionosphere mapping is not required, and the antenna used can be much much smaller (an antenna's length determines the frequency that it will transmit a frequency correctly). This brings me to another point, GPS units are small, therefore the antenna inside is small, therefore it transmits on frequencies well higher than that of HF so must be line of sight. VHF will not even be transmitted well over hilly terrain, definitely not is the receiving station is in a valley, and UHF has no chance. You must literally be able to draw a straight line between stations. So GPS being used with land based transmitting stations is an uneducated, unintelligent, and impossible explanation.
Also, this wins.