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RF signals in tunnels - RF Cafe Forums
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Leo
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Post subject: RF signals in tunnels
Posted: Wed Oct 05, 2005 7:53 am
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Hello: I read somewhere (maybe on RF Cafe)
about special "leaky" coaxial cable that is used
in tunnels to broadcast signals. Do you know if
this is only used for things like AM/FM radio and
emergency channels, or can it also be used for cell
phone signals? How about does anyone know
of specific instances where it is being used now?
I'm thinking about a SBIR (Small Business Innovation
Research) project proposal for Homeland Security
and want to get as much info as possible, including
where it is actually working now. Thanks,
Leo
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kanling |
Post subject:
Posted: Wed Oct 05, 2005 11:25 am
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Colonel |
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Joined: Mon Jul 18, 2005
4:31 pm Posts: 43 Location: Baltimore, MD
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Leaky coax is very old technology that has been
used for years. Yes, it is currently used for cell
phones and pagers in subway tunnels all over the
place. You will be able to get some examples
from some of the vendors. Andrew calls theirs "Radiax"
and Times Microwave also has a product. I'm sure
there are others.
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Leo |
Post subject:
Posted: Wed Oct 05, 2005 12:48 pm
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Thank kanling, I'll look there. Leo
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Audun |
Post subject:
Posted: Mon Jun 02, 2008 4:36 am
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Joined: Mon Jun 02, 2008
2:29 am Posts: 1 |
Hi Leo I saw your post on the RF Cafe. Did you
manage to find more information about leaky coax
cables. I am working on a 868 MHz antenna and is
interest in any kind of information on this subject.
Audun
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FSomma |
Post subject:
Posted: Mon Jun 02, 2008 8:23 pm
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soyola |
Post subject: Leaky Cable Vs Fiber Optic
Posted: Mon Oct 27, 2008 5:50 pm
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Joined: Mon Oct 27, 2008
5:32 pm Posts: 1 Location: Los Angeles,
CA |
kanling is right. Leaky cables are very old technology.
Some companies started using fiber optic cable to
transmit signals and build repeater stations along
the way.
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nubbage |
Post subject:
Posted: Wed Oct 29, 2008 4:46 am
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General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 304 Location: London UK
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Hi Leo The 22 mile-long Channel Tunnel between
UK and France supports all emergengy communication
for the trains and response services using a "Leaky
Feeder" coaxial system for VHF and UHF. The system
was put in by a JV between Motorola and Andrew Antenna
Corp. many years ago (during tunnel construction
work in 1987). More modern approaches certainly
focus on fibre-optic cables with drop/insert modems
whereby the optical side is directly modulated /demodulated
with the full radio spectrum, then a small antenna
radiates the radio signal locally (eg TETRA). A
power feed is obviously necessary on copper cables
bundled with the optical fibre.
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nubbage |
Post subject:
Posted: Thu Oct 30, 2008 6:58 am
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General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 304 Location: London UK
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Hi Leo Two further afterthoughts: 1. You
might find some interesting, although probably "academic"
treatment of the topic in IEEE Trans. 1986 EMC-28
(3) a paper entitled "Experimental Study of Radio
Characteristics in an Underground Street and Corridors"
by Yamaguchi, Abe and Sekiguchi. 2. There is
a report in the British amateur radio journal RadCom
of tests at VHF, UHF and 1300MHz done in connection
with emergency services and the National Rail Network
in the UK. I will try to locate the reference date.
I recall it concluded that 1300MHz was a very effective
part of the spectrum for free radiation through
concrete-lined rail tunnels to support rail accident
rescue operations.
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Posted 11/12/2012
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