MYERSTON@kl.sri.com (HECTOR MYERSTON) (04/13/89)
Phones sold in the US are limited by the FCC to freq/power
combinations which equate to 700 to 1000 feet free-space ranges. As
someone pointed out, actual ranges tend to be much worse and transmissions
highly subject to interference. There is a "Range Extender" passive
antenna made by Valor which inmproves range but only marginally.
Overseas, more powerful transmitters are used and ranges up
to 50 Km are common. There ARE place in the US which sell them for
"use outside the US". One such is Phone Masters in LA. I do not
recommend trying then here, you will probably interfere with someone
and the FCC will eventually track you down.
Telcos also use various narrow-band microwave sets to save
stringing wire to remote locations. These sets are not available
to the public.
[I tried to reply to tmk@research.att.com but the net
didn't like the address]