Post by Druid Hills Radio on May 1, 2017 15:06:50 GMT
License free operation in the 88 to 108 MHz band is regulated by section §15.239 of the FCC rules. These rules specifically state that:
Emissions from the intentional radiator shall be confined within a band 200 kHz wide centered on the operating frequency. The 200 kHz band shall lie wholly within the frequency range of 88-108 MHz. This means that the transmitter follows the same standards for FM broadcasting and in no case shall a center frequency be either 88.0 or 108.0. 88.1 through 107.9 are the legal frequencies. Part 15 operation in TV Channel 6 spectrum such as on 87.7 and 87.9 is prohibited under 15.209(a) of the rules. This means ANY power on 87.7 and 87.9 is not permitted. Emissions within the permitted 200 kHz band shall not exceed 250 microvolts per meter at 3 meters. The emission limit in this paragraph is based on measurement instrumentation employing an average detector. (In other words, the output of the transmitter is based on field strength and not on power. Very regularly do we hear people think that the limit on FM is 100 milliwatts or a specific watt value. It's not. It is a combination of your power output and the efficiency of the attached antenna. Keep in mind that there is no restriction on antenna height as long as the field strength measured at 3 meters is 250 microvolts or less.)
The field strength of emissions radiated on a frequency outside the specified 200 kHz band shall not exceed the general radiated limits in §15.209. (The transmitter must be stable and must suppress any out of band emissions. A very common problem with illegal transmitters is that they produce spurious emissions in the spectrum used for aeronautical communications and navigation 108~136 MHz and thus can cause interference to safety of life communications. Despite the changes in FCC field enforcement, interference to aviation is still a huge priority at the Commission.)
Emissions from the intentional radiator shall be confined within a band 200 kHz wide centered on the operating frequency. The 200 kHz band shall lie wholly within the frequency range of 88-108 MHz. This means that the transmitter follows the same standards for FM broadcasting and in no case shall a center frequency be either 88.0 or 108.0. 88.1 through 107.9 are the legal frequencies. Part 15 operation in TV Channel 6 spectrum such as on 87.7 and 87.9 is prohibited under 15.209(a) of the rules. This means ANY power on 87.7 and 87.9 is not permitted. Emissions within the permitted 200 kHz band shall not exceed 250 microvolts per meter at 3 meters. The emission limit in this paragraph is based on measurement instrumentation employing an average detector. (In other words, the output of the transmitter is based on field strength and not on power. Very regularly do we hear people think that the limit on FM is 100 milliwatts or a specific watt value. It's not. It is a combination of your power output and the efficiency of the attached antenna. Keep in mind that there is no restriction on antenna height as long as the field strength measured at 3 meters is 250 microvolts or less.)
The field strength of emissions radiated on a frequency outside the specified 200 kHz band shall not exceed the general radiated limits in §15.209. (The transmitter must be stable and must suppress any out of band emissions. A very common problem with illegal transmitters is that they produce spurious emissions in the spectrum used for aeronautical communications and navigation 108~136 MHz and thus can cause interference to safety of life communications. Despite the changes in FCC field enforcement, interference to aviation is still a huge priority at the Commission.)
