Quote:
Originally Posted by dragoon500ly
The main radio associated with these stations is the AN/PRC-70 which is listed as having a 4,000km with the AS-2975 antenna for CW only. Range for SSB and AM is up to 800 kilometres, range for FM is 40 kilometres.
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One thing to remember about these ranges is that they are for two specific antennas, one a rod (monopole) and the other a dipole. Nothing prevents the use of a properly tuned directional antenna, like a yagi antenna, to extent the range of repeaters well beyond those ranges. The biggest difference is that the monopole and dipole antenna have radiation patterns that work much better for broadcast than the highly directional nature of a yagi.
If the intent of the repeater is to facilitate point to point communications, the yagi would be the way to go. If they send and receive to a large area around the ground station, you would use a monopole or dipole antenna. Not having the module to read the intended use for the repeaters, I cannot say with any certainty what the spacing of repeaters would be. It is possible that they place different antennas at the repeaters to increase coverage while minimizing number of bases. For instance, there may be a number of stations that use dipole antennas that are wider spaced with a large, but acceptable, marginal signal strength that are interconnected via a network of directional repeaters. This would allow the directional repeaters to operate a lower power and therefore be smaller than the broadcast bases.