You may wish to try using an FM transmitter, like the one below:
There are lots of devices available in a wide range of prices, so this one may not be the best. Also, the plug on this device may not match your television; so you should verify that the device you decide to buy is compatible with the connector on your TV.
To use a device like this, perform the following:
* Connect the power cord or plug to the power source. For this example, that would be a 12 volt
DC cigarette lighter socket.
* Plug the adapter cable into the earphone jack on your TV set.
* Select the FM radio frequency on which you wish to transmit. Pick a channel that's not in use and has the least interference. You may need to experiment to get the best signal, after you get everything hooked up.
* Turn on the FM stereo in your Airstream and tune to the frequency you selected.
Some of these devices work better than others, so you may wish to buy from a store that has a liberal return policy and several models that you can try.