At this time during this election season I wish to take definite stands on certain transmitter issues.
The FM Rule 15.239 is nonsense. It is nonsense for two reasons. Nonsense Reason No. 1 is that anyone goofy enough to attempt doing something with so weak a transmitter is obviously not able to verify that the field strength meets 15.239. Nonsense Reason # 2 is that the only way to get a solid, multipath free signal using a 15.239 transmitter is to locate it one-foot from the FM radio. The sillyness of 15.239 falls on the FCC.
Carrier Current is dangerous. Radio hobbyists should avoid experimenting with AC powerlines in hope of reaching several extra feet with an AM radio signal. If a member of your family insists on dabbling in carrier current get a big fat life insurance policy on them and there's a good chance you will come into some money.
Only three Part 15 categories deserve full attention:
15.219 AM band broadcasting, 15.217 Long Wave broadcast, and 15.225 Short Wave Radio.
Those three Part 15 categories are worth pursuing for the increased range they provide and being alive for the experience.
In closing may I say the FCC is not your friend. They have jobs, they don't want you causing work.
Problem is that no one will listen to long wave or short wave and how many people even in your area even have one(shortwave or longwave radio), or would go out and buy one. Plus the fidelity is half as good as AM(medium wave) and there's still the noise interference.
The part 15-239 was only set up to allow a wireless signal to get to FM radios in your house and the yard....not to broadcast to the neighbourhood...unfortunately.
Fortunately, here in Canada, you can get a hobby FM station off the ground because of BETS-1 which as Tim's tests showed, you have to have more or less 2000 to 2500uV/M at 3 meters to get 100uV/M at 30 meters away(BETS-1) A whole lot more than part 15.
Even with AM, getting the range of up to a mile providing you have the ability to do the more elaborate set up (like having a house and property), is outside and clear line of site. Not getting into other houses or buildings, and that's on a car radio not a "regular" radio especially if it's plugged in to A/C in a home. And at night...forget it.
No the FCC is not your friend, they are the police, although we are brought up to think the police are your friends. But if you are a corporation with lots of money then the FCC is your friend.
Mark