I agree with George that using an off the shelf wireless digital transmitter / receiver is the way to go here. I bought a set that has one stereo transmitter and two wireless headphones that (a few projects down the road) will be gutted and the innards will be an RF link from my computer to an homebrew amp on the other side of my office.
I don't know what band it operates on. 902-928 MHz now has an amateur allocation, but it may be secondary, and won't be used much until surplus equipment starts hitting the market in larger quantities.
An FM band stereo composite signal has a very wide bandwidth - wide bandwidth means lots of extra noise in the receiver - so the very nature of the transmitted signal inherently limits its range, especially at the allowable field strength permitted by the FCC. I don't know what you could do to overcome this, except to increase the field strength - either more power or better antenna or both. FM broadcast is not a high fidelity medium anyway - the 19 KHz pilot signal that is doubled to form the 38 Khz difference subcarrier will limit the audio bandwidth to maybe 17 or 18 Khz tops. Premphasis for noise reduction and dynamic range are also issues.
A caveat about tinkering with an FM broadcast band transmitter: A few years back, a guy around here built one that covered about a square mile. Unfortunately for him, he also had a spur dead center on one of two of the approach / departure frequencies for the local regional airport / air national guard facility. Finding hidden transmitters is a competitive sport in ham radio, and this transmitter was found within minutes. Because of the proximity of the FM BCB to aeronautical and public service frequencies, I would be very circumspect about modifying one or building an amp for one without some RF experience and acess to a spectrum analyzer or some other means of checking for spurious or harmonic output. In fact, I just wouldn't do it - it's not legal and there are better ways to skin the cat.
Win W5JAG
I don't know what band it operates on. 902-928 MHz now has an amateur allocation, but it may be secondary, and won't be used much until surplus equipment starts hitting the market in larger quantities.
An FM band stereo composite signal has a very wide bandwidth - wide bandwidth means lots of extra noise in the receiver - so the very nature of the transmitted signal inherently limits its range, especially at the allowable field strength permitted by the FCC. I don't know what you could do to overcome this, except to increase the field strength - either more power or better antenna or both. FM broadcast is not a high fidelity medium anyway - the 19 KHz pilot signal that is doubled to form the 38 Khz difference subcarrier will limit the audio bandwidth to maybe 17 or 18 Khz tops. Premphasis for noise reduction and dynamic range are also issues.
A caveat about tinkering with an FM broadcast band transmitter: A few years back, a guy around here built one that covered about a square mile. Unfortunately for him, he also had a spur dead center on one of two of the approach / departure frequencies for the local regional airport / air national guard facility. Finding hidden transmitters is a competitive sport in ham radio, and this transmitter was found within minutes. Because of the proximity of the FM BCB to aeronautical and public service frequencies, I would be very circumspect about modifying one or building an amp for one without some RF experience and acess to a spectrum analyzer or some other means of checking for spurious or harmonic output. In fact, I just wouldn't do it - it's not legal and there are better ways to skin the cat.
Win W5JAG