"Ron J" wrote:
The idea behind it is that it's suppose to monitor local traffic
conditions using a video feed and then it will broadcast some
pre-recorded messages via the FM transmitter warning on-
coming drivers of potential road blocks.

If this application is a real project, and intended for the US, and you need
it to "broadcast" to FM receivers over an area that would be fairly useful
for this purpose, then a station license will be needed from the FCC.

Unlicensed transmitters in the 88-108 MHz band are restricted under 47 CFR
Part 15 to radiated field strengths not exceeding 250 µV/m at a distance of
three meters in all directions from the transmit antenna. The transmit
antenna needs to radiate only ~18.8 nanowatts in order to generate that
field. FCC OET Bulletin 63 is a good resource for this situation
http://www.fcc.gov/Bureaus/Engineeri...3/oet63rev.pdf .

Anyway, I'm supposed to determine the range of the
FM transmitter by measuring the field strength.

The propagation paths for these circumstances will be line-of-sight, so
except for reflections, received field strength will be inversely
proportional to the distance from the transmit antenna. A system operating
legally under Part 15 would produce a field of about 2 µV/m at a distance of
about 1,400 feet. So if the airborne tx system elevation was 500 feet, its
ability to cover a significant area on the ground with useful signal
strengths will be reduced.

Hopefully this background information will be useful.

RF http://rfry.org