so - if you are getting just a few blocks anyway, why not use a bunch of broadcastVision FM transmitters?
I bought 5 on ebay, certified and all, 50 bucks for the lot. not power supplies, but a quick trip to the surplus store fixed me right up.
They seem to have gone up a bit in price: Broadcast Vision BV2001 Stereo Low Power FM is now between 50/each to 150.00 each 🙂
In my Post 10 I mentioned that the r-f bandwidth of a 3-meter, center-fed dipole for the AM broadcast band will be relatively narrow. This will be true even at the top end of the band.
Below is a graph showing this, and its effect on the output audio of AM receivers.
(My apologies to Ermi Roos.)
A bandwidth of +/-5kHz seems just about right for medium wave AM, and a pre-emphasis curve at the upper end of the audio bandpass could be employed to "season to taste."
An added benefit of so narrow a bandwidth will serve to reject unwanted reception of RF energy from radio transmitters nearby on the dial.
Also, is it not true that a narrower bandwidth has the advantage of better distance penetration?
A bandwidth of +/-5kHz seems just about right for medium wave AM, ...
The r-f bandwidth shown in the chart means that 5 kHz audio in a perfect AM receiver would be about 19 dB below the value at 100 Hz. That would take an extreme amount of pre-emphasis to overcome, and would reduce low frequency modulation of the transmitter by about 19 dB in order to avoid overmodulating at 5 kHz.
An added benefit of so narrow a bandwidth will serve to reject unwanted reception of RF energy from radio transmitters nearby on the dial.
Unfortunately, not so. This r-f response is a characteristic of the transmit system, not the receiver. The receiver response could still accept other signals lying within the r-f bandwidth of the receiver.
Also, is it not true that a narrower bandwidth has the advantage of better distance penetration?
Within limits, narrow r-f bandwidth of an AM receiver can improve the intelligibility of the demodulated waveform, because that improves its signal-to-noise ratio. But that is a function of the receiver, not the transmitter.