Ramsey Electronics FM10A - Manual (Page 24)

In fact, the most significant distance in the above chart is the 1.9 µV signal
strength permissible at 1260 feet (about 1/4 mile), covering a circular area of
about 114 acres. A quick glance at stereo FM receiver specifications shows
typical sensitivity of 1.7 µV before considering high-gain antennas or
preamplifiers. Your non-licensed signal can provide serious competition to a
public broadcast station fifty miles away, a station which someone in your
neighborhood may have set up a special antenna to enjoy.
Calibrated "field strength meters" such as described in the ARRL Radio
Amateur's Handbook can detect signals down to about 100 microvolts. To
measure RF field strength below such a level, professional or laboratory
equipment and sensitive receivers are required. A "sensitive" receiver
responds to a signal of 1 or even .5 microvolt "delivered" to the receiver input
by antenna. If the antenna is not good, the receiver cannot respond to the
presence of fractions of a microvolt of RF energy.
SUMMARY
The present edition of Part 15 of the FCC rules does not provide detailed
guidance on ALL aspects of using a low-power transmitter such as the
FM10A. The main point is that you may not cause any interference
whatsoever to licensed broadcast services and that you must be willing to
put up with any interference that you may experience.
In addition to operations not requiring authorization, you also have the
option of writing a clear and polite letter to the FCC Engineer-in-Charge of
your local district, describing your intended operation. Mention the operating
frequency and planned hours of operation. This could be a good step to take
if your project is on behalf of a school, Scout or community group.
If you become further fascinated with the service rendered by low-power
broadcasting, other FCC regulations explain how to apply for a license or
other authorization which may permit you to upgrade your FM10A or other
equipment to accomplish any objective which the FCC sees to be in the
public interest and not interfering with other authorized uses of the radio
spectrum.
Lawful use suggestions for the FM10A
1. Build and adjust this kit strictly according to the published
instructions.
2. Use the whip antenna supplied with the Ramsey case set, CFM.
3. Do not modify your kit in any way.