Cost of leaky cable

Don't know the cost but have been thinking about how long it's been since leaky cable transmission has been talked about here.

Like carrier current, leaky cable opens a whole other way of doing Part 15.

I want to say the last time I saw leaky coax it wasn't cheap.

think the leaky cable manufacturing went way of the DoDo when LPB died.

Is there a limit as to how long a leaky coax can be?  If not yes it opens doors.

In terms of engineering, the limit is when there is just enough power being injected at the fed end of the coax to just meet the field strength limit while at the other end there is barely enough signal radiating to be useful.  DC can be passed on the coax and an amplifier can be put between segments so if inline amplifiers are used the limit is when the noise from n amplifiers makes a unusable signal to noise ratio in the n+1’th length of leaky coax.

You can make a leaky cable any length.

Trouble is, you can only install the leaky cable on your own property.

It can be buried in the ground or suspended in the air, but when you come to the property line you either stop, or:

a.) negotiate with neighbors to continue the cable through their yards, or;

b.) pay the power pole utility the going rate to have leaky cable carried along the poles to whatever distance you can afford.

Principle of operation

"A leaky feeder communication system consists of a coaxial cable run along tunnels which emits and receives radio waves, functioning as an extended antenna. The cable is "leaky" in that it has gaps or slots in its outer conductor to allow the radio signal to leak into or out of the cable along its entire length. Because of this leakage of signal, line amplifiers are required to be inserted at regular intervals, typically every 350 to 500 metres, to boost the signal back up to acceptable levels. The signal is usually picked up by portable transceivers carried by personnel. Transmissions from the transceivers are picked up by the feeder and carried to other parts of the tunnel, allowing two-way radio communication throughout the tunnel system.

The system has a limited range and because of the frequency it uses (typically VHF or UHF), transmissions cannot pass through solid rock, which limits the system to a line-of-sight application. It does, however, allow two-way mobile communication. " (500 meters translates roughly to 1600 feet.)

The following is a pdf. explaining typical use and power loss in long runs of leaky coax.
Predicting Propagation Loss from leaky cable terminated with an indoor antenna.

Leaking cable is effective in sending and receiving signals in confined spaces or where traditional antennas are not desirable. The FCC allows for se of leaky cable for tranmission around a property of a campus, home or business. Coal mines here in Kentucky use it to communicate over two way radio's and to pipe AM/FM radio signals underground to miners.

The longer the run of feeder cable (leaky coax) the weaker the rf field becomes, so to cover more than 1600 feet you would have to install amplifiers every 2000 feet to make up for the loss.

If some how an individual wanted to cover their apartment complex or neighborhood with leaky cable, there would be so many hurdles and hoops to jump through. The red tape would be maddening, in the case of covering a block or two, the city would have to get involved, utilities commissions and the like would have so many questions about the idea of anyone besides the cable and phone company stringing leaky cables around town.

I suppose a proposal would be needed including the frequency , rf power, maintainance and feasablility of providing a leaky radio station to a small community when carrier current is more suited for this scenario.

In my case, using leaky coax just to cover 4 houses really doesn't seem worth the price of leaky cable :
Pricing:    $46.00 + $1.50 per Foot
Unit Price:    $796.00   Total: $796.00

That price was a quote for 500 feet of Andrew Radiax, so not a realistic way for a hobby station to go about providing an FM service to only a handful of homes as well as an STL to an AM transmitter.

I think the best way to handle this in my case is the 5.8 Ghz AV link for under $100 US Dollars.

A nightmare.
Leaky Cable is just that, leaky. If you did manage to run enough cable to cover a town that cable needs to be maintained and since it is leaky that also opens up a whole new can of worms.

Moisture, be it humidtiy, rain or flooding, water can get into the cable just as easily as rf can and will follow the path of the coax to a low spot and just sit there. Over time it will rot the cable from the inside as well as causing damage to equiptment such as the inline amps.

Hi Guys: Here is a web site that you might want to check out.

http://www.themindfactory.com/tmf/Products/Leaky_Coax/leaky_coax.html

Also i did a manual on this as well it's on the ALPB Site under LPB Manuals  and look for LPB leaky coax Tech Notes.

Station 8