[sci.electronics] radio reception

i8bla@vax87.auc.dk (07/21/89)

In article <Jul.19.14.48.15.1989.439@athos.rutgers.edu>, gutherz@athos.rutgers.edu (Matt Gutherz) writes:
> 
> A while back (months) there was a discussion about improving
> radio reception in basements etc.  Someone posted a solution
> using 2 antenna and some coax.  Does anyone have the posting
> or know the specs for the antenna?  Thanks in advance.
> 
> 
> Matt gutherz@jove.rutgers.edu



Radio propagation inside buildings.

The system you mention is probably the 'leeky feeder'. This can
be used in tunnels, where you place an antenna outside to pick-
up the radio signal, an retransmit it on the coax cable. If the
cable has some slots, you will experience an electromagnetic
field, radiating from the cable. The problem is to get a field
with no severe power fades. Such systems are already imple-
mentet in Europe, retransmitting FM radio broadcast.

I have an extra question: Does anyone have any experience
in radio propagation inside buildings at 2 GHz as a function
of building materials? (Bricks, concrete, reinforced concrete,
wood, glas etc). I would be glad to hear about any practical
experiments or theoretically modelling.

Bo L. Andersen
Aalborg University
Denmark

roy@phri.UUCP (Roy Smith) (07/23/89)

In article <81@vax87.auc.dk> i8bla@vax87.auc.dk writes:
> The system you mention is probably the 'leeky feeder'. This can be used
> in tunnels, where you place an antenna outside to pickup the radio
> signal, an retransmit it on the coax cable. If the cable has some slots,
> you will experience an electromagnetic field, radiating from the cable.

	The Port Authority of New York and New Jersey does this in the
Lincoln Tunnel.  Interestingly enough, my reception is *better* in the
tunnel than outside.  It's probably because I've got a trashy AM set which
barely works and in the tunnel there is less random interference.

	The interesting part of the system is the the PA can break into the
normal re-broadcast for emergency messages.  They do this, I believe, on
every AM channel.
-- 
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
{att,philabs,cmcl2,rutgers,hombre}!phri!roy -or- roy@alanine.phri.nyu.edu
"The connector is the network"

john@stiatl.UUCP (John DeArmond) (07/24/89)

In article <3890@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
> The system you mention is probably the 'leeky feeder'. This can be used
> in tunnels, where you place an antenna outside to pickup the radio
> signal, an retransmit it on the coax cable. If the cable has some slots,
> you will experience an electromagnetic field, radiating from the cable.

This is known by the brand name Leakiax.  It is standard fare in most
of the nuclear plants I've work.  It is used to provide 2-way radio
contact in all the shielded rooms in these plants.  

The Leakiax I looked at consisted of 7/8" hardline with a narrow 
longitudinial slot cut in the shield.  This slot was segmented into
sections about a foot long.  Don't know if this was some sort of tuning
or just manufacturing convenience.
-- 
John De Armond, WD4OQC                     | Manual? ... What manual ?!? 
Sales Technologies, Inc.    Atlanta, GA    | This is Unix, My son, You 
...!gatech!stiatl!john    **I am the NRA** | just GOTTA Know!!! 

gutherz@athos.rutgers.edu (Matt Gutherz) (08/16/89)

A while back (months) there was a discussion about improving
radio recetion in basements etc.  Someone posted a solution
using 2 antenna and some coax.  Does anyone have the posting
or know the specs for the antenna?  Thanks in advance.


Matt gutherz@jove.rutgers.edu