transmission down a tunnel
 

Hi there,

Could someone explain in simple terms (I know next to nothing about
radio waves or electricity) what interference and attenuation problems
might arise in the following scenario:

A remote controlled vehicle in a cable tunnel environment housing
several 400 kV circuits, communicating to an operator located in a
control room 5 km away.

The remote control vehicle is a monorail carriage and the information
relayed back to the control room includes commands (forward/backward)
and a video feed.

The reason why I am asking is because I went down such a tunnel and
the chap who was in charge of operations mentionned that they had to
install light reflectors to convert the radio signal into an optical
signal because of signal attenuation and that there was a problem with
interference with the electrical field generated by the cables.

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?

Thanks

transmission down a tunnel
 

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

transmission down a tunnel
 

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