Newsgroups: sci.electronics.misc
Subject: Re: TV RF transmitter
References: <[email protected]>
[email protected] (Yoni) writes:

> Hi
> 
> I have a TV in a room without a TV receptacle. I would like to buy a
> device (transmitter) that I could plug into a TV receptacle located in
> another room, which would in turn transfer the RF signal  to a
> receiver plugged into the RF input of the TV (or radio).  can anyone
> tell me where I can buy such a device? Would such a device be very
> difficult to build?

I quess that there is not such device you are looking for in the
market. And it would be hard to build for seral reasons, especially 
if you want it to be legal to use (not intefering with neighbourhood). 

One way to do it is the following (legal, but complicated and expensive).
You need the following parts:

1. A TV tuner with IR remote controller (a normal VCR works here well)
2. A wireless video/audio + IR signal link (there are many sich products 
   on the market, they transfer on video signal, audio and IR signals 
   wirelessly from one place to another using microwaves for AV transmission,
   typical operating range 20-30 meters, usually RF for IR signals)
3. TV modulator


On the room where TV outlet is:

Your TV tuner connects to the room where you have the TV outlet. 
The video and audio outputs from the tuner go to the wireless 
audio/video link inputs. The IR signal output from the video link 
is connected to the tuner IR receiver (place the IR transmitter LED 
on the wireless device near tuner IR receiver on the device). 

On the room where TV is:

The output from the wireless A/V-link go to the video modulator 
device output. From the modulator you get the RF signal you feed 
to the TV antenna input to ivew this. Tune the TV to channel the 
modulator gives out. Not you don't need your TV remote to 
change channels. Use the TV tuner remote (pointed to wireless 
A/D-link device) to change the channels on the TV tuner. The 
channel that tuner device is tuner to can be now seen on your 
TV screen. 



The illegal way would be the following: 

Take two wideband directional TV antennas. 
Connect one antenna to your TV antenna input. 
Place another antenna to the room where your  
antenna outlet is. 
Make the antennas to point to each other. 
Place a suitable powerful wideband RF amplifier 
between your antenna outlet and that TV antenna 
nearby. With this construction (amplifier and 
antenna) you have effectively created a small 
wideband TV transmitter. On the other end the antenna 
receives the signal your transmitter sent out. 
In real life applications the TV transmission on 
the air screw up the thibgs pretty much 
(you are trying to transmit at the same frequency 
there is already signal on the air, this happens 
if you amplify what is coming from house antenna, 
if you have cable TV on your house you can have 
different situation). 
So in practice you might get somethign going through 
with a luck, but this kind of system would be highly 
illegal, because is it would be a non-licensed 
TV transmitter that interferes with the existing 
TV/radio services. So sooner or later you operate, 
somebody will notice the interference and authorities 
will catch you from this. The fines for causign this 
kinf of interference can be high. 
So using this method is highly NOT adviced. 


-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/