§  73.683   Field strength contours and presumptive determination of field
strength at individual locations.

   (a) In the authorization of TV stations, two field strength contours
   are considered. These are specified as Grade A and Grade B and indicate
   the approximate extent of coverage over average terrain in the absence
   of interference from other television stations. Under actual
   conditions, the true coverage may vary greatly from these estimates
   because the terrain over any specific path is expected to be different
   from the average terrain on which the field strength charts were based.
   The required field strength, F (50,50), in dB above one micro-volt per
   meter (dBu) for the Grade A and Grade B contours are as follows:
                  Grade A (dBu) Grade B (dBu)
   Channels 2-6              68            47
   Channels 7-13             71            56
   Channels 14-69            74            64

   (b) It should be realized that the F (50,50) curves when used for
   Channels 14-69 are not based on measured data at distances beyond about
   48.3 kilometers (30 miles). Theory would indicate that the field
   strengths for Channels 14-69 should decrease more rapidly with distance
   beyond the horizon than for Channels 2-6, and modification of the
   curves for Channels 14-69 may be expected as a result of measurements
   to be made at a later date. For these reasons, the curves should be
   used with appreciation of their limitations in estimating levels of
   field strength. Further, the actual extent of service will usually be
   less than indicated by these estimates due to interference from other
   stations. Because of these factors, the predicted field strength
   contours give no assurance of service to any specific percentage of
   receiver locations within the distances indicated. In licensing
   proceedings these variations will not be considered.

   (c) The field strength contours will be considered for the following
   purposes only:

   (1) In the estimation of coverage resulting from the selection of a
   particular transmitter site by an applicant for a TV station.

   (2) In connection with problems of coverage arising out of application
   of § 73.3555.

   (3) In determining compliance with § 73.685(a) concerning the minimum
   field strength to be provided over the principal community to be
   served.

   (d) For purposes of determining the eligibility of individual
   households for satellite retransmission of distant network signals
   under the copyright law provisions of 17 U.S.C. 119(d)(10)(A), field
   strength shall be determined by the Individual Location Longley-Rice
   (ILLR) propagation prediction model. Guidance for use of the ILLR model
   for these purposes is provided in OET Bulletin No. 72. This document is
   available through the Internet on the FCC Home Page at
   http://www.fcc.gov.

   (e) In the case of measurements to determine the eligibility of
   individual households to receive satellite retransmission of distant
   network signals under the copyright law provisions of 17 U.S.C.
   119(d)(10), if a satellite carrier and the network station or stations
   asserting that the retransmission of a signal of a distant network
   station is prohibited are unable to agree on a person to conduct the
   test, the American Radio Relay League, Inc., 225 Main Street,
   Newington, CT 06111-1494, shall designate the person or organization to
   conduct measurements based on the technical qualifications and
   independence of proposed testers. The satellite carrier and network
   station shall propose testers and provide their qualifications in
   writing to the American Radio Relay League (ARRL). Individuals may also
   volunteer themselves as testers by submitting their qualifications to
   the ARRL. The ARRL can be reached by telephone at 860-594-0200, or
   email at hq@arrl.org.

   (f) A satellite carrier is exempt from the verification requirements of
   47 U.S.C. 339(c)(4)(A) with respect to a test requested by a satellite
   subscriber to whom the retransmission of the signals of local broadcast
   stations is available under 47 U.S.C. 338 from such carrier. The
   definitions of satellite carrier, subscriber, and local market
   contained in 47 CFR 76.66(a) apply to this paragraph (f).

   [ 44 FR 36039 , June 20, 1979, as amended at  47 FR 35990 , Aug. 18, 1982;
    50 FR 23699 , June 5, 1985;  50 FR 32416 , Aug. 12, 1985;  65 FR 36641 ,
   June 9, 2000;  70 FR 21670 , Apr. 27, 2005]