Is IR repeater over coax possible?

I have 5 TV's throughout the house that I use. Since I only use one at a time, I would like to use my digital cable box to feed them all. This part is not a problem. The problem is trying to control the box with the IR remote when it is located in a different room. I have build IR repeater circuits in the past using a dedicated wire. Has anyone used the existing coax within the house to carry the repeated signal back to the equipment to be controlled? Is this possible without interferring with the cable signal? Is there another way to do this that would be easier and cheaper short of re-wiring the house?

Another way is to use a
Wireless IR Remote Control Extender

Radio Shack has them
The first room is $44 and each additional room is $20.

hi,
Look at this link for options.
I use the radio linkers using a standard IR remote to control my digibox from different rooms,

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NOTE: **broken link removed**

Perfectly possible, and commonplace - Sky Satellite boxes in the UK provide that exact facility - with two RF poutputs on the back, one of them (RF2) has the option of supplying 9V DC power up the coax, and receiving remote control signals back down the same coax, on an RF carrier signal.

Does anyone have a schematic to build such a thing?

You'll spend less time and money buying the units that eric linked. If you don't have the money to buy them then you don't have the money to build them.