Leaky Coax

[SK500]

I’m working on a project that involves the transfer of data (Control signals) to a number of moving targets on a track; this will be an Ethernet network.

Recently a co-worker suggested using “leaky coax-cables” to transfer the Ethernet data.
I admit to not knowing much about this, but a quick search resulted in some answers…I fond that leaky coax has been used for many years in mines and tunnels where communications is required underground. Is this a two way communication? How does it work? (I have read some descriptions, but I’d like to hear your take on it)

Ps: I was thinking RS 485 could be another candidate, are there any other broadband communications method I’m missing here? ... Keeping in mind the Ethernet network and
moving targets.

 

[itsmoked]

There are a lot of off-the-shelf (OTS) devices to accomplish this. RF, Bluetooth, Ethernet, optical. Just google "wireless rs232".

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[SK500]

Forgot to mention but his is not an underground system.

 

[SK500]

In a leaky coax cable what is the function of the "messenger wire"?

From what I can gather, here's my take on how this lcx cable functions. Data is transfered at a high speeds, a string of 1s and 0s create an electromagnetic wave that is used by some receiver device to perform some function based on that signal. Am I right?

Now the messenger wire...is that a way that the recvr device can communicate back? if yes the how so?
thanks
SK

 

[Skogsgurra]

My take is that it is nothing but a long antenna. The beauty of it is that you can distribute RF energy along the coax and energy is leaking out through slots in the cable so you can listen to radio, talk over your mobile or anything that uses RF transmission. But you can not feed the ones and zeroes directly into the leaky coax. Have to put them on a carrier first (like a RF signal with some modulation).

Used in tunnels, mostly, for the simple reason that an antenna doesn't radiate very well into tunnels. An antenna that creates a useful signal strength at a few miles distance in a tunnel would probably be lethal when you get close to it.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Comcokid]

In the situations where it is used, leaky coax takes the place of the antenna in a wireless system. Think of it like this - A normal antenna is like a garden hose connected to a sprinkler (if onmidirectional), or to a nozzle (if directional). A leaky coax is like a garden hose hooked up to a long soaker hose.

However, you indicate these are "control signals". When you get to wireless situations, you need to consider data latency and data reilability. In any wireless system, you might have dead spots, interference, noise, data corruption, etc. You need to consider carefully what will happen in your system when these issues arise. You haven't given specifics of your end application, but you don't want to end up with your "moving targets" out of control because of the typical wireless issues.