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Prometheus Fact Sheet

Alternatives to Low Power FM

[Unlicensed Legal FM] [Pirate Broadcasting] [Unlicensed Legal AM]
[Internet Radio][Digital Radio][Buying a Commercial FM or AM License]
[Starting a New Full Power FM Radio Station] [Buying Time on a Commercial Radio Station]
[Shortwave and Amateur Radio]

Unlicensed Legal AM

The legal limit for AM broadcasting is 100 milliwatts, with a maximum antenna length of about 10 feet (this is the infamous Part 15 FCC rule). In our experience with low power AM, the results have been disappointing. Ordinarily, this power is capable of going about 250 feet, but the audio quality becomes very poor after 100 ft.

However, there are some professional "type-accepted" transmitters available that claim to reach 1.5 miles (type-accepted transmitters are devices that have gotten approval from the FCC for its design) From our experience, these coverage claims are pretty dubious. Though we haven't seen every low power AM transmitter out on the market, what we have seen comes nowhere close to that kind of coverage radius. A note about Part 15 - it does not require that you use a transmitter that has been type-accepted, so it is "legal" to use a homemade transmitter or a kit. Part 15 specifies very strict operating parameters. If you are using a kit or a homemade transmitter, an FCC inspector is much more likely to do a very careful inspection, and they will probably find something wrong with it. Generally, the FCC will not scrutinize a type accepted transmitter, because they already know the design will function legally and reliably.

When salespeople describe the range of their products, they often discusst the furthest out anyone has ever heard it. That may not be your practical range. Range generally has much more to do with the type of receiver that you are trying to use. (See the section below "It's the Reception That Counts- the Range of a Broadcast Signal).

There is an excellent reference on low power AM that anyone who wants to pursue this route should read hear. Look under engineering. Crash, the person who runs the site, is very helpful if you ask questions.

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