This article is from the Low Power Broadcasting FAQ, by Rick Harrison firstname.lastname@example.org with numerous contributions by others.
This depends on what country you are in. The situation varies from
place to place, so you should check with a lawyer or with the agency
that regulates broadcasting in your part of the world before turning
on any transmitter. Don't rely entirely on web pages or usenet
newsgroups for such critical information.
In some European countries (e.g. the Netherlands), you can be arrested
for merely possessing an unlicensed transmitter. In Ireland,
unlicensed broadcasting is unlawful but stations that don't cause
interference are seldom prosecuted. In Taiwan, the authorities have
recently threatened to imprison unlicensed broadcasters. Indonesia
generally tolerates unlicensed broadcasts on shortwave. Canada and
Japan have made it possible for people to get licenses for very low
power FM stations if the licensees promise to provide programming that
is not available from mainstream outlets.
In the United States, Title 47 of the Code of Federal Regulations
(Part 15, subpart C) indicates that unlicensed broadcasting is limited
to microscopic power levels. The power limit for unlicensed FM
transmissions is a signal strength of 250 microvolts per meter,
measured 3 meters from the transmitting antenna. At this power level,
stereo reception with a good signal to noise ratio is only possible
within a 100 foot radius, and an average car radio can barely detect
the signal at a distance of 100 meters. On the AM band, the limit is
0.1 watt and an antenna system no more than 3 meters long; this
provides a range of 2 or 3 city blocks for cheap receivers, farther
for high-quality radios.
Some have argued that the strictness of these regulations violates the
US Constitution (footnote 1) and the UN Declaration of Human
Rights.(footnote 2) Others have said that the federal government does
not (or should not) have jurisdiction over low-power transmissions
that do not cross state lines. There have been many court battles over
the FCC's regulations, and no doubt there will be many more.
Apart from the Part 15 rules mentioned above, legal unlicensed options
include carrier current transmission (using the power lines as an
antenna system); cable FM broadcasting (working in conjunction with
your local cable TV system); and burying special "leaky" coaxial cable
to use as an AM transmitting antenna on privately owned land. Panaxis
and LPB can provide more information about legal options.
1. From the Bill of Rights: "Congress shall make no law respecting
an establishment of religion, or prohibiting the free exercise
thereof; or abridging the freedom of speech, or of the press..."
2. Article 19: "Everyone has the right to freedom of opinion and
expression; this right includes freedom to hold opinions without
interference and to seek, receive and impart information and ideas
through any media and regardless of frontiers."