VHF/UHF Digital modes
Like the HF bands, adding a computer to the hamshack can add new modes to the operator's options.
On the VHF bands, the same modes are also feasible but there is a difference in the band conditions. Whereas on HF it is common to have interference from other stations or severe fading of signals due to unusual propagation or "skip" conditions, on VHF signals tend to be received without interference. This has led to the development of digital signal processing (DSP) programs that work in conjunction with sound cards to effectively "dig" signals out of noise. Modes such as JT65 and others have been developed by Joe Taylor K1JT to enable amateurs to have radio contacts with stations they cannot hear with the ear.
This development has made it possible for relatively modestly equipped VHF/UHF stations to make contacts via reflections off the moon, something that was previously the realm of only the best equipped stations, with huge antenna arrays or large dishes, combined with power at the legal limit .
Experiments conducted almost daily by amateurs on 144.3 MHz in Australia during 2007 onwards, have also shown that these digital modes can make possible contacts using reflections from meteor ionisation trails. Signals reflected off these trails can be quite loud but short lived.
There is more development occurring daily in this area so again the reader is recommended to conduct further searches and keep reading.
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