reply to alkizmo
Re: Hopeless or possible? HDTV OTA The purpose of an antenna is not to "get distance". Its purpose is to get as much as possible of the transmitted signal while ignoring as much noise as possible.
I'm not an HF expert but I very much doubt that a single yagi antenna will get anywhere near the same amount of useful signal as these multi-element antennas.
The yagi while directional isn't as sensitive to direction and a slight deviation from optimal will probably still get you a good signal (provided it is strong or close). However in order to get the same gain as a multi-element UHF antenna you would have to combine several yagi antennas. This is not easy but it is possible and if you search on the Internet (look for vertical and horizontal stacking of antennas) there are reports from people who have done that. If you do that you have the same gains but also the same requirement for proper alignment as with a multi-element antenna.
The multi-element antenna is more challenging. Any deviation from the correct alignment will cause the signal to arrive phase shifted on some of the dipoles. That phase shift will cause the signals to partially cancel each other out (instead of the signals being combined to a much stronger signal).
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