A recent question about the subject of radios, and their ranges, uses and
limitations, led to some interesting answers. Some readers might find this
of interest, thought I, so I'll post it. Doubtless some other readers will
shake their heads and groan at the thought of this lunatic putting up more
horrendously incorrect information; please don't bother writing to
complain, I've researched this to the extent I feel justifies the subject,
and with the usual caveat that Rifts is a game and as such, realism should
only intrude as game enjoyment warrants, off we go.
Range of radio broadcasts depends greatly on terrain and available power; there is no set range a radio can use, since range will be specific to the radio in question, the terrain around it, atmospheric effects and available power. A vehicle mounted communications system, for example, in north-eastern U.S. style terrain can expect a maximum range of perhaps 10 miles. This can increase five or ten fold if they take advantage of RRB (Radio ReBroacast) units, increase power to the system, and/or use terrain effectively.
The differentiation between long range and directional radios is meaningless. Radio is, by its nature, omnidirectional. Range is another matter; it is quite possible for a very long range radio system to connect its operators in North America with a recieving station in Africa or South America, but this sort of equipment is extremely power-hungry and very, very, very large, far larger than could be mounted on any vehicle, and is the definition of Immobile.
Recieving range is entirely dependent upon the power of the broadcaster; however far he can send his signals, that far you can detect his signals. However, note that receivers must be tuned to the frequencies the broadcaster is using; long range systems use low frequencies, while short range systems use high frequencies, and a receiver can only be tuned to receive a very narrow range of electromagnetic frequencies. If you have a short-range receiver, such as a commercial walkie-talkie type device, all kinds of very long range radio signals could be passing by and you would never know it.
Height is not intrinsically valuable in terms of range. What makes height advantageous is the ability to escape ground clutter. A radio signal can have its range reduced to 5 to 10 percent of total if it has to pass through buildings, trees and similar heavy debris; a fair sized hill can completely stop a radio signal, a problem which plagues military troops in places like Bosnia. Broadcasting from a high location allows you to avoid the detrimental effect of ground clutter and get the full range from your equipment.
Direction Finding, or DF, equipment is quite easily capable of detecting any electromagnetic emission in a very wide range. Military forces of most nations today have specialized EW units capable of DFing enemy radio broadcasts and radar emissions. Further, DFing gear is man-portable. In the Twilight Games section of the Realm I've put up Armageddon, a 1/300 scale SF tactical wargame which, among other things, describes fairly accurately the role and effect of DFing and EW in modern warfare (although I had to reduce ranges a fair whack to fit on the tabletop).
So, then, are the typical Radio communications ranges of Rifts robots (500 miles in the case of the UAR-1) realistic? The quick answer is, well, Kevin Siembieda is an imagination man, not a physicist. 500 miles is well beyond the range possible for radio equipment mounted on a moving object. It's worth mentioning that radio equipment with that range exists, but the transmission array weighs about as much as a UAR-1 and the dish is 40' across, easy. Microwave or laser communications might well have ranges like that, but Rectilinear Propegation states that such systems will require the target to be in LOS of the transmitter; ie, 500 miles in a straight line with very little in between. Besides, Kev clearly states several times that this is Radio equipment, not advanced communications gear. Divide the ranges Kev provides by 10 and you'll be close.
Does this eliminate the possibility of phenomenal advances in radio
technology, which might eventually have such ranges with such small units?
All things are possible, but I wouldn't bank on it. However, as I've said
repeatedly in other areas, this is a game and as such, use whatever
works best for your game.