I did not finish my last email to this list, as I had to leave for an
appointment.
If anyone wants to transmit audio over a fairly large area, FCC part 15 is much
more lenient for unlicensed transmissions on the AM broadcast band.
The power limit is 100 milliwatts input to the final stage of the transmitter.
Maximum antenna length, including ground leads, is 3 meters. The part 15 device
may not cause harmful interference with any licensed station.
To maximize efficiency, which maximizes coverage, choose an unoccupied
frequency as high in the AM BC band as you can. Vertical antennas, of a given
size, tend to be more efficient as the frequency increases, because of a higher
radiation resistance and lower capacitive reactance. The lower X sub C
requires less lossy inductive loading in order to effect an impedance match.
You may also learn a lot about vertical antennas, their loading and impedance
matching.
I have a legal, part 15 AM transmitter in our home, that I can feed with any
audio source desired. This includes ham rig, communications receiver or
satellite radio. We live on just under 4 acres and I can hear my transmitter
anywhere in the yard with a Sony Walkman or a GE Superadio portable. I have
read about legal, part 15 AM installations that produce a listenable signal
almost a mile from the antenna. Your mileage may vary. Local ground
conductivity is a variable. Have some fun.
Gary
KzeroCX
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