In a message dated 97-08-10 01:46:54 EDT,
aa0cy@robertwanderer.gardnerville.nv.us writes:
> Of course, as has been pointed out, Andrews and others make coaxial
> cables (e.g. Radiax{TM}) designed to "leak." It is used in the Holland and
> Lincoln Tunnels (and I think the Brooklyn Battery and Queens Midtown
> tunnels too) to allow motorists tp listen to their AM/FM radios
(especially
> for traffic reports).
Leaky coax is also used for communications systems where antennas may
not be possible or desired. Again, these are mostly tunnel applications. Bus
tunnels and subway tunnels sometimes use this technique for their vehicle's
communications.
In the case of Andrew cable, there are actual big ovals of shield cut out
of the cable to allow the center conductor signal to 'leak' out. There is
some amount of attenuation but in these cases the distances are pretty short.
These are generally in the UHF and above (8-900 mHz) frequencies.
73, Steve K7LXC
TOWER TECH -- professional tower supplies for amateurs
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