Re: fm transmitter
At least give Antaean3000 credit for finding a frequency stable design although I suspect getting hold of some of the parts may not be as easy as it seems.
Take note of Audioguru's warning about pre-emphasis. I'll try to explain it in laymans terms: You probably noticed a weak FM signal has background hiss, some of this is actually in the transmission and receiver circuits but the vast majority comes from random signals being picked up and amplified from the antenna. The hiss is most noticeable in the mid and high sound spectrum, you can see this if you play with tone controls on your FM radio, the bass control makes little difference to the noise but the treble has a pronounced effect. In FM audio transmission we take advantage of this by using pre-emphasis at the transmitter and de-emphasis at the receiver. As their names suggest, some frequencies are emphasized and reduced in the process. Pre-emphasis at the transmitter boosts the mid and high sound frequencies by a fixed amount so the 'real' transmission sounds harsh and 'tinny', to compensate, the receiver reduces the frequencies by the same amount in the de-emphasis circuit. The combination restores a flat frequency response as far as the sound is concerned but the background hiss which is introduced between the transmitter and receiver output is quite dramatically reduced. You might like to think of it as turning the treble control right down on your receiver and turning it right up on the transmitter to compensate.
If you use the design as it is, it will certainly work but because it doesn't have pre-emphasis, the sound will be transmitted as it is but the receiver will still try to reduce the volume of higher pitched notes. the result will be very muffled 'muddy' sounds.
As far as power is concerned, even 1 Watt could reach several miles and unless you live in a metal box, it will spread outside in all directions. Your neighbors would be able to listen in and it's highly likely you would cause interference to others. There are strict licensing conditions you have to comply with, you can get the details from the Ofcom web site. Even if you ignore the license, to broadcast around the home you wouldn't need more than 5 - 10mW, in other words less than 1% of the power you are proposing.
Brian.