Part 15 Station

The Rangemaster AM1000 unit we use has been certified by the FCC and is legal to use as long as it is installed properly. However there are questions that come up on a regular basis. There is a statement on the FCC website that says that Part 15 transmitters only get 500 foot of range. Many ask how transmitters such as the AM1000 can legally get 1-2 miles range in view of this statement. After talking with FCC officials about the statement basically the answer is that most AM and FM Part 15 transmitters are certified under Part 15.209 which is a radiation limitation. A Part 15 transmitter certified under this rule would get about 500 feet or so of range. AM transmitters certified under Part 15.209 are allowed 24000/F(Khz) micro volts per meter (at 30 meters) field strength. An example of this sort of transmitter would be a childs toy or wireless microphone. However the AM1000 AM transmitter was certified under Part 15.219 which is not a radiation limitation but is a power and antenna length limitation. The power limit is .1 watt and the antenna length limit is 3 meters. There is no range or height limit for a Part 15.219 transmitter. With this allowed combination much greater ranges are possible, though it requires tune up and setting the power by a competent technician. Generally you can’t buy a Part 15.219 certified transmitter bubble packed at the department store. Because the AM1000 has a removable antenna and adjustable power, instruction to be installed by competent personal was a condition of certification.

Rule 15.215 (a) clarifies this:
"(a) The regulations in Sections 15.217-15.255 provide alternatives to the general radiated emission limits for intentional radiators operating in specified frequency bands. Unless otherwise stated, there are no restrictions as to the types of operation permitted under these sections."

Generally the Spirit of the Part 15 law seems to be not to cause interference to a licensed station. Of course you should follow FCC law and fully cooperate with the FCC. Here is subpart 15.219:

”Section 15.219 Operation in the band 510 - 1705 kHz.

(a) The total input power to the final radio frequency stage (exclusive of filament or heaterpower) shall not exceed 100 milliwatts.

(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3meters.

(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.”

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