dangerd wrote:

I guess what I want to know is what is happening to that radio signal
(I think it is a UHF signal) which means that they have to convert it
to a light signal?

Also, can you beam a signal down a tunnel (40m below ground) which
twists and turns both in the vertical and horizontal directions?

The common to provide radio communication in a tunnel is to use a leakage
coaxial cable which isn't 100% shielded and has slots along in the
shielding.

Regards,

Ralf
--
Vy 73 es 55 de Ralf, DL2MRB

Ralf Ballis, DL2MRB wrote:
"The common (method) to provide radio communication in a tunnel is to
use a leakage coaxial cable which isn`t 100% shielded and has slots
along in the shielding."

Yes. Andrew Corp. in the U.S.A. used to get a high price for such a
special cable. 300-ohm TV twinlead is cheap and works very well too when
used between a radio and a load to communicate with other 2-way radios
along the twinlead route in tunnels and elsewhere.

Best regards, Richard Harrison, KB5WZI