From HF Underground
The FMT4R as branded by Scosche is a small, Part 15 transmitter, with an output of approximately 250uW, with supply voltage of 3V DC.
It is able to transmit on multiple frequencies, from 88.7MHz up to 108.0 MHz, adjustable via DIP switches. As supplied by the manufacture, the antenna is a random wire, which consists of the shield for the audio out line.
On batteries (2 AAA type), the unit can operate for 15 hours (tested) continuous, at full power out. After that, RF out will continue to drop due to a dropping in input voltage.
This unit is very easy to modify for both more power out, and better range. By adjusting the power supply voltage up to 5V DC, it can put 750uW out.
The antenna can be modified to a proper dipole, by soldering the one leg of the dipole to the solder pad for the audio in shield, and the other leg to the chassis ground point. By adding two holes to the plastic chassis, the legs of the antenna can be fed in opposite directions, with the transmitter being at the dipole feed point.
As tested, the unit installed at the feed point of a vertical dipole, a range of 3/4 to 1 mile was observed, when attic mounted. Outside of 1/2 mile, fading was observed. This was caused most likely due to obstructions. All in all, this unit makes for a very good community radio station, offering coverage of a relatively decent sized neighborhood.