Total posts : 45366
Here’s my $0.02:
1. Having a good antenna ground (actually a counterpoise on an elevated installation) makes a lot of difference in range. Rangemaster has a drawing of a good ground plane system on this page:
The transmitter should be located in or near the center of the ground plane, so the “To Trans” lead shown in the diagram is as short as possible. The FCC considers the ground LEAD from the transmitter to the ground SYSTEM (or PLANE) to be part of the 3-meter limit.
The Rangemaster drawing indicates 64 or more radials of #12 or larger wire. However, if your situation demands thinner wire or fewer radials, then go with as much as you can put up. The better your ground, the more use you can make out of your site (which is pretty good from your description). With a good antenna and ground, you should get at least 1 mile range, 1.5 is definitely possible.
Given the antenna restrictions, your frequency will also affect range. A 3-meter antenna is massively short anywhere in the AM broadcast band, but it will be much less so toward the high end. Prevailing wisdom is to be at least above 1500 kHz, and preferably above 1600, which is in the less-populated “extended” band.
Receiving setup also affects range. Encourage your listeners to get a good receiver (the GE SupeRadio III is one of the best for performance and value) or a manufactured passive loop antenna such as:
* The Select-A-Tenna (get one that goes to 1700, some older ones don’t)
* The Terk AM-1000 Advantage
* The Radio Shack 15-1853 (discontinued, available used but seen less than the others)
The GE SupeRadio III has a large internal ferrite rod loop antenna. The loops mentioned above may not really improve the GE’s performance, but will help on many other radios.
2. The idea behind multiple transmitters is to have them at different locations. I don’t think two at the same place will really help you. If you are going to run multiple transmitters on the same frequency, they must be synchronized in phase and frequency to avoid interference. If you are interested in this, Manteca Community Radio is using a 2-transmitter setup, I think with a wireless link between them. Their Web page is at:
The owner / manager / chief cook / dishwasher is our member MLR.