I would like to transfer digital serial data over an existing analog TV cable. How do I do that?
In order to transfer some data to a device's control lines remotely, I'm looking into inexpensive, but reliable methods that would use existing in-place system.
Suppose there is a cable running in the client's home that transfers analog RF-band TV signals (e.g. from an RF modulator into an old TV). I'm looking for a DIY solution, or a prebuilt consumer-level product that would be able to send (and receive) some serial data over the standard analog TV coaxial cables.
I would like this system to coexist with the audio/video signals (VHF or UHF) on the line, and don't interfere with the current devices. Additionally, power will be delivered to the devices at each end. I'd also like the transmitters to be able to transmit at different channels, and decode the data back by selecting the channel.
I require both sending and receiving (either full-duplex or half-duplex) serial data (UART, TTL, etc) at a simple baud-rate (e.g. 9600, or if possible 115200 bps), reliably.
Question: Would I be able to build a DIY solution, or design an inexpensive board to handle my request? Are there any solutions that would make this possible?
I was not able to find such a device or any schematics by searching the web.
Since I'm not familiar with the analog RF-band TV, I do not know how I would design something, if anything. I would prefer either an existing schematics, or an existing product that would do this. What route should I go?
(n.b. If possible, I would like to have multiple transmitters and decoders.)