Making contact by FM radio

[Skvez]

The Size of transmitter (the physical box) shouldn't be an issue for a fixed location.
As Skean stated the Size of the aerial can be an issue, you get better distance with a taller aerial but you can conceal an aerial if you don't mind a loss of effective range.
The power of the transmitter directly affects the volume you can cover with the transmission. The standard 4W CB will get you over 10 miles (in today's noisy environment) some commercial FM radio stations are pushing thousands of Watts.

To be "the Village Vigil Voice" you probably only need a 100mW transmitter.
The Original Post was about getting/making a small transmitter that could transmit on the standard FM band so that others in the neighbourhood could be informed of looters/raiders natural disaster risks in the area.
I see little point in being able to transmit on a HAM radio when nearly no-one else out there has a HAM radio to listen to you.