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LPFM Report and Order: Difference between revisions
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=== Second and third adjacent channel protections === | === Second and third adjacent channel protections === | ||
When LPFM was originally proposed, the FCC stated that stations would be required to protect other stations on co-channel (same frequency) and first-adjacent channels (+/- 200 kHz). The FCC was inclined to authorize the service without any second-adjacent channel (+/- 400 kHz) or third-adjacent channel (+/- 600 kHz) standards. The FCC stated that a strong case could be made for not requiring third-adjacent channel protections as there would be little risk of interference to existing radio services as the interference would be very small and only occur in the immediate vicinity of the LPFM station or if the LPFM station was located at the outer edge of the full-service station's protected contour where the full-power station's signal would be the weakest. The FCC noted that third-adjacent channel protection was eliminated for certain grandfathered and short-spaced full-power stations in 1997. On balance, the FCC stated that creating opportunities for a new LPFM station should outweigh any small risks of interference to and from LP-1000 and LP-100 stations. | |||
For second adjacent channel stations, the FCC notes that grandfathered short-spaced FM facilities were permitted to modify their facilities without regard to second or third-adjacent channels from 1964 to 1987 and then from 1997 to the present and that no interference complaints were received as a result of those modifications and they found that the small risk of interference was outweighed by improved service. | |||
=== Technical studies === | |||
Technical studies were filed in response to the NPRM by the Consumer Electronics Manufacturers Association (CEMA) under the auspices of National Public Radio, CEMA and the Corporation for Public Broadcasting; the NAB; and a third study conducted by Broadcast Signal Lab, LLP for the National Lawyers' Guild, Committee on Democratic Communications (NLG). In addition, the FCC's Office of Engineering and Technology (OET) completed a study on FM receivers. | |||
==== CEMA Study ==== | |||
The CEMA Study tested 16 consumer receivers including 5 automobile radios, 5 home hi-fi tuners or receivers, 3 portable stereo systems, 2 portable radios and one "walkman" style radio. Receivers were tested under a number of conditions including co-channel, first, second and third-adjacent channel interference. CEMA's determination was that proposals to eliminate second and third adjacent channels could result in significant interference to current and future FM stations and threaten the deployment of future digital audio services and therefore recommends that the second and third adjacent channel (and intermediate frequency) protections be maintained. | |||
==== NAB Study ==== | |||
The NAB Study tested 28 FM radios including 8 automobile, 5 component, 5 portable and 5 clock radios. In their study, they had found that "15 to 22" of the 28 receivers would experience interference on third-adjacent channels and "22 to 23" of the 28 receivers would experience interference on second-adjacent channels. They concluded that the FCC receivers generally do not perform up to FCC interference standards and that the FCC's assumptions that these restrictions could be eliminated for FM stations are incorrect. | |||
==== NLG Study ==== | |||
The NLG study examined a sample of 10 radios including 3 higher prices radios (generally above $150), 5 lower priced radios and 2 factory installed car radios. NLG observed that the car radios and higher priced radios performed far better than one would predict on the FCC interference ratios and that substantial signal strengths were required to cause second, third and forth-adjacent channel interference. The lower priced radios tended to "straddle" the FCC interference protection ratios. The NLG study found that more aggressive modulation of the undesired signal did not cause a significant increase in interference, especially on second, third and fourth adjacent channels and that less costly radios were more susceptible to modulation induced interference than more costly radios. All radios tested for co-channel and first-adjacent channel interference matched or exceeded the FCC interference protection ratios. Higher priced radios tend to withstand second-adjacent channel interference between than lower priced radios. Higher priced radios and car radios withstood undesired signal levels higher than the FCC interference protection standards. The poorest performing radios were susceptible to second-adjacent channel undesired signal ratios at levels lower than the levels that affected the best performers. Third adjacent channel interference was slightly less challenging to most radios than second-adjacent channel interference. Higher priced radios and car radios tended to fare better than the lower prices radios. | |||
==== OET Study ==== | |||
The FCC's OET conducted a study with 21 radios including 5 small moderate cost portable and "boom box" receivers, 7 automobile receivers and 9 moderately expensive home stereo type receivers. No inexpensive receivers without an antenna input were used. OET found that nearly all of the receivers in the sample appear to meet or exceed the current second-adjacent channel protection ratios and exceeds the third-adjacent channel protection by a wide margin. | |||
==== FCC conclusions ==== | |||
The FCC determined that the test data concludes that any risk of interference from LPFM stations of 100 watts is small and, on balance, is outweighed by the benefits of the new service. They concluded it was not necessary to apply third-adjacent channel protections as it would not result in significant new interference to existing FM stations nor does it believe such operations will have an adverse effect on digital IBOC signals. The FCC found that the risk from second-adjacent channel interference was "somewhat higher" and therefore they would retain the second-adjacent channel protection requirements. | |||
=== Other technical standards and provisions === | === Other technical standards and provisions === | ||
==== Power and height ==== | |||
The FCC determined that if an LPFM station operates from a height above average terrain that is higher than 30 meters, their assigned effective radiated power would be reduced in order to produce a service contour that is appropriate for the LPFM service class. | |||
==== Directional antennas ==== | |||
Citing the facts that facilities using directional antennas are subject to strict installation and pattern requirements, the impact on staff resources for processing these applications and due to the fact that LPFM uses distance separation as opposed to contours, the FCC did not authorize directional antennas for the LPFM service. | |||
==== Transmission standards ==== | |||
The FCC did inquire whether LPFM stations should have a different transmission standard such as reduced bandwidth. The FCC would determine that LPFM would use the same transmission standards as full-service FM stations. LPFM stations may engage in monophonic or stereophonic broadcasting and may use subcarriers when the FM signal is on the air. | |||
==== Antenna polarization ==== | |||
LPFM stations were permitted to operate horizontally polarized, vertically polarized, circularly polarized or elliptically polarized antennas. Normally in the full-service (with some exceptions for NCE stations near a Channel 6 TV station), antennas must include a minimum of a horizontal element to them. This flexibility will make it easier for LPFM stations to select an antenna for their station. | |||
==== Protection of AM radio radiation patterns ==== | |||
Antenna structure construction within 3.2 kilometers (2 miles) of a directional AM station or 0.8 kilometers (0.5 miles) of a nondirectional AM station will subject LPFM stations to the AM protection requirements to assure that the constructed tower structure does not adversely affect the AM signal pattern through reflections produced by the new structure. | |||
==== Antenna Structure Registration ==== | |||
Antenna structures that are in excess of 61 meters above ground level and those along designated glide slopes in respect to nearby airports are subject to Antenna Structure Registration requirements. | |||
==== Blanketing interference ==== | |||
For the first year after the commencement of transmissions with new or modified facilities LPFM stations will be responsible for handling blanketing interference complaints. For LP-100 stations, this is approximately 125 meters from the transmitter site and for LP-10 stations, about 39 meters. | |||
==== Transmitter certification ==== | |||
The FCC will require transmitters in the LPFM service to be type certified. Type certification would prevent the use of transmitters with excessive bandwidth or modulation, spurious emissions, excessive power output or insufficient frequency stability, which could cause interference to other existing stations. | |||
==== Unattended operation ==== | |||
The FCC anticipates that many LPFM stations will be operated unattended (no duty operator at the transmitter or studio site during all hours of operation). LPFM stations operating unattended will be required to advise the FCC by simple letter of the unattended operation and to provide an address and telephone number where a responsible party could be reached at such times. The responsible party must be able to turn off the transmitter within 3 hours of receiving notice from the FCC that the equipment is not functioning properly. | |||
==== Station logs ==== | |||
Requirement for station logs will be minimal for LPFM stations. LPFM station logs will contain only the following entries: | |||
# Daily observation of proper function of tower obstruction lighting (if required by rules); | |||
# Dates and a brief explanation regarding station outages due to equipment malfunctioning, servicing or replacement; | |||
# Any operation not in accordance with the station license; | |||
# Receipt of the weekly Emergency Alert System test; | |||
# Name of person making the entry. | |||
==== Environmental requirements ==== | |||
To protect occupied areas from radio frequency radiation, the FCC has specific standards. There are additional standards for other environmental issues including but not limited to construction at sites with historical significance. The FCC will create a simplified process to assist LPFM applicants with this. | |||
==== Radio astronomy installation notifications ==== | |||
Like with all other radio services, LPFM stations will be required to notify and coordinate their operations and provide protections to the radio quiet zones in West Virginia and Colorado. LPFM applicants in Puerto Rico will need to coordinate their operations with the Arecibo Observatory. | |||
== Application processing == | == Application processing == | ||