On 9/21/05 9:56 PM, in article , "Larry"
wrote:

-Name Withheld For Security Concerns wrote in
:

Hello!
Our boat has several UHF radio's that are used to communicate
between
compartments. I thought the steel bulkheads would have acted as a
faraday cage and prevented any communication. Any thought on why the
UHF radios work as well as they do?

-Thanks



On UHF, the wavelength is only about 12", which fits very handily through
any hatch a human can fit through. The passageways act like waveguides to
signals at this frequency or even higher.

Even if the watertight hatch is closed, as far as RF is concerned, the
rubber gasket between the coaming and hatch make a slot antenna and UHF
will, although attenuated some, make it through the rubber insulator to the
other side of the hatch....with enough signal left to be usable.

As long as nothing totally metal gets between your radios, they'll work,
probably, ok. Many things can be done to improve range inside the ship.
You can install passive repeaters between decks or between inside and
outside by simply installing UHF 1/4 wave antennas connected together by
coax cable from A deck to B deck. Hang them from the overhead wiring
harnesses out of the way. Signals that hit one antenna will be
transferred, poorly but usably, to the other.

Large ships might also contain higher powered repeaters with antennas
strategically placed inside the hull.


Thanks Larry and Terry. This makes sense, and the question has been bugging
me for a while. I feel less dumber by the minute.

-Regards