§ 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.
   Such eligibility determinations shall consider only the signals of network
   stations located in the subscriber's Designated Market Area. Guidance for
   use of the ILLR model in predicting the field strength of analog television
   signals for such determinations is provided in OET Bulletin No. 72 (stations
   operating with analog signals include some Class A stations licensed under
   part 73 of this chapter and some licensed low power TV and TV translator
   stations that operate under part 74 of this chapter). Guidance for use of
   the  ILLR model in predicting the field strength of digital television
   signals for such determinations is provided in OET Bulletin No. 73 (stations
   operating with digital signals include all full service stations and some
   Class A stations that operate under part 73 of this chapter and some low
   power TV and TV translator stations that operate under Part 74 of this
   chapter). OET Bulletin No. 72 and OET Bulletin No. 73 are available at the
   FCC's  Headquarters Building, 445 12th St., SW., Reference Information
   Center, Room CY-A257, Washington, DC, or at the FCC's Office of Engineering
   and Technology (OET) Web site:
   http://www.fcc.gov/oet/info/documents/bulletins/.

   (e) If a location was predicted to be unserved by a local network station
   using a version of the ILLR model specified in OET Bulletin No. 72 or OET
   Bulletin  No. 73, as appropriate, and the satellite subscriber at that
   location is receiving a distant signal affiliated with the same network from
   its satellite provider, the satellite subscriber shall remain eligible for
   receiving the distant signal from its satellite provider if that location is
   subsequently predicted to be served by the local station due to either a
   change in the ILLR model or a change in the station's operations that change
   its coverage.

   (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;  75 FR 80363 , Dec. 22, 2010]

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