Broadcast range of an FM radio station with given transmit power
OK lets provide a line-of-sight non-multi-path (no reflected energy that may cause peaking and nulling, as airplanes may do, or large drones may cause) link analysis.

Assume:

you want good FM audio, so at least 20dB SNR at the receivers

gain of 1 (0dB) receiver antennas ( easy to get 5 or 10 dB more gain, if needed by the more distant homes, with fancy antennas)

bandwidth of 200,000 Hertz in the receivers

losses between antenna and the first receiver amplifier: 0dB; there will be some, but a bit of PI matching will compensate

noise figure (thermal noise) of the first receiver antenna: 3dB (should be real easy to achieve at 100MHz)

Now compute the required energy out of the receiver antenna

-174dBm / Hertz bandwidth

+53 dB   for the 200,000Hz bandwidth

+20 dB for the signal-noise-ratio for clean music

+0  dB for losses/matching-up-transform(PI)

+3 dB  Noise Figure of the first amplifier



-174 +53 +20 +0 +3 = -174 + 76 = -98 dBm  &lt;&lt;&lt; Minimum Received Power

Now for the PathLoss for a line-of-sight path, no rain attenuation, no multipathing, good antenna alignment

At 100MHz (wavelength = 3 meters), and a 300 meter path, with the energy spreading out into a hemisphere with 4*pi*(range)^2  surface area, we use this formula

PathLoss = +22dB + 10 * log10[(Distance/wavelength)^2]

or

PathLoss = +22dB + 20 * log10(Distance/wavelength)

and for Distance = 300 meters , and wavelength = 3 meters, we have

PathLoss = +22dB + 20*log10(300/3) = +22 + 20*2 = 62dB PathLoss

What must the Transmitter power be?

Simply add the PathLoss to the Minimum Received Power

+62 dB + (-98 dBm) = -36 dBm &lt;&lt;&lt; Minumum Transmitted power
if no rain nor multipath nor antenna bad alignment

Helpful numbers: 0dBm is 1 milliWatt. If -36dBm, you'd have 3 factors of 0.1x (each of 10dB), and 2 factors 0.5x (each of 3dB), computed like this

0.1 * 0.1 * 0.1 * 0.5 * 0.5 = 0.001 * 0.25 = 0.00025x

which is 1milliWatt * 0.00025 = 0.25 microwatt.

If you run a suitable vertical antenna up a tree, not against the tree trunk, but hanging from a limb with coax running from the TX circuit to the antenna, and feed that antenna with 1 milliWatt (about 0.223 volt RMS or 0.632 volt PeakPeak) you will have 30 dB or more margin.

Now----are you understanding the regulations in your state?

What about lightning strikes, onto the antennas?

Notice you may detect large drones with the multipathing caused by reflections off the wiring from central body to the rotor motors. 

You might even place FM-resonant dipoles around in your village, to collect and re-radiate FM energy. This re-radiation of RF energy will contribute to the richness of the multipath environment. By quenching and then un-quenching (un-dampening?) each of your dipoles on a fixed schedule, you may better detect the drone presence. In essence, you are using these dipoles (with no receiver attaced, just a CMOS switch and dampening resistor) as "radar" Transmitters that cause changes in the RF FM amplitude and phasing. Since YOU are controlling the "radar" timing, you get to use the amplitude/phase changes as information to detect the drone.

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By the way, there is/was a 67KHz subcarrier that is often used for TEXT/stock_quotes/etc.

You can use that for sending messages out to all the homes in the village, if there is no cellphone service.