Sec. 21.902  Frequency interference.

    (a) All applicants, conditional licensees, and licensees shall make 
exceptional efforts to avoid harmful interference to other users and to 
avoid blocking potential adjacent channel use in the same city and 
cochannel use in nearby cities. In areas where major cities are in close 
proximity, careful consideration should be given to minimum power 
requirements and to the location, height, and radiation pattern of the 
transmitting antenna. Licensees, conditional licensees, and applicants 
are expected to cooperate fully in attempting to resolve problems of 
potential interference before bringing the matter to the attention of 
the Commission.
    (b) As a condition for use of frequency in this service, each 
applicant, conditional licensee, and licensee is required to:
    (1) Not enter into any lease or contract or otherwise take any 
action that would unreasonably prohibit location of another station's 
transmitting antenna at any given site inside its own protected service 
area.
    (2) Cooperate fully and in good faith to resolve interference and 
transmission security problems.
    (3) Engineer the system to provide at least 45 dB of cochannel 
interference protection within the 56.33 km (35 mile) protected service 
area of any authorized or previously proposed station that transmit, or 
may transmit, signals for standard television reception.
    (4) Engineer the station to provide at least 0 dB of adjacent 
channel interference protection within the 56.33 km (35 mile) protected 
service area of any authorized or previously proposed station that 
transmits, or may transmit, signals for standard television reception.
    (5)(i) Engineer the station to limit the calculated free space power 
flux density to -73 dBW/m2 at the boundary of a 56.33 km (35 
mile) protected service area, where there is an unobstructed signal path 
from the transmitting antenna to the boundary; or alternatively, obtain 
the written consent of the entity authorized for the adjoining area to 
exceed the -73 dBW/m2 limiting signal strength at the common 
boundary.
    (ii) In determining signal path conditions, the following shall be 
used: a 9.1 meter (30 feet) receiving antenna height, the transmitting 
antenna height, terrain elevations and 4/3 earth radius propagation 
conditions.
    (6) If a proposed station is within 80 km (50 miles) of the Canadian 
or Mexican border, the station must be designed to meet the requirements 
set forth in international treaties.
    (c) The following interference studies must be prepared, must be 
available to the Commission upon request, and may be submitted as part 
of any application:

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    (1) An analysis of the potential for harmful interference within the 
56.33 km (35 mile) protected service areas of any authorized or 
previously proposed incumbent station:
    (i) If the coordinates of the applicant's proposed transmitter are 
within 160.94 km (100 miles) of the center coordinates of any authorized 
or previously proposed incumbent station with protected service area of 
56.33 km (35 miles) as specified in Sec. 21.902(d); or
    (ii) If the great circle path between the applicant's proposed 
transmitter and the protected service area of any authorized, or 
previously-proposed, cochannel or adjacent-channel station(s) is within 
241.4 kilometers or less and 90 percent or more of the path is over 
water or within 16.1 kilometers of the coast or shoreline of the 
Atlantic Ocean, the Pacific Ocean, the Gulf of Mexico, any of the Great 
Lakes, or any bay associated with any of the above (see Secs. 21.901(a) 
and 74.902 of this chapter);
    (2) Applicants may design interference studies in any manner that 
demonstrates the avoidance of harmful interference, as defined in this 
subpart.
    (i) In lieu of interference studies, applicants may submit in 
accordance with Sec. 21.938 a written statement of no objection to the 
operation of the MDS station.
    (ii) The Commission may direct applicants to submit interference 
studies of a specific nature.
    (3) Except for new stations proposed in applications filed after 
September 15, 1995, in the case of a proposal to operate a non-colocated 
station within the protected service area of an authorized, or 
previously proposed, adjacent channel station, an analysis that 
identifies the areas within the protected service areas of both the 
authorized or previously proposed adjacent channel station and the 
proposed station that cannot be protected as specified in 
Sec. 21.902(b)(4) and an explanation of why the proposed station cannot 
be colocated with the existing or previously proposed station.
    (4) In the case of a proposal for use of channel 2, an analysis of 
the potential for harmful interference with any authorized point-to-
point station located within 80.5 kilometers (50 miles) which utilizes 
the 2160-2162 MHz band; and
    (d)(1) Subject to the limitations contained in paragraph (e) of this 
section, each MDS station licensee shall be protected from harmful 
electrical interference, as determined by the theoretical calculations, 
within a protected service area of which the boundary will be 56.3255 
kilometers (35 miles) from the transmitter site.
    (2) As of September 15, 1995, the location of these protected 
service area boundaries shall become fixed. The center of the circular 
area shall be the geographic latitude and longitude of the transmitting 
antenna site specified in station authorizations or previously proposed 
applications filed at the Commission before September 15, 1995. 
Subsequent transmitter site changes will not change the location of the 
56.3255 kilometers (35 mile) protected service area boundaries.
    (e) No MDS licensee will be protected from harmful interference 
caused by:
    (1) Any station with an earlier filing date.
    (2) Any station that was authorized before July 1984.
    (3) Any multichannel MDS station whose application was pending on 
September 9, 1983.
    (f) In addressing potential harmful interference in this service, 
the following definitions, procedures and other criteria shall apply:
    (1) Co-channel interference is defined as the ratio of the desired 
signal to the undesired signal present in the desired channel, at the 
output of a reference receiving antenna oriented to receive the maximum 
desired signal. Harmful interference will be considered present when a 
free space calculation for an unobstructed signal path determines that 
this ratio is less than 45 dB.
    (2) Adjacent channel interference is defined as the ratio of the 
desired signal to undesired signal present in an adjacent channel, at 
the output of a reference receiving antenna oriented to receive the 
maximum desired signal level. Harmful interference will be considered 
present when a free space calculation for an unobstructed signal path 
determines that this ratio is less than 0 dB. In the alternative, 
harmful interference will be considered present

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for an Instructional Television Fixed Service (ITFS) station constructed 
before May 26, 1983, when a free space calculation determines that this 
ratio is less than 10 dB, unless the license for a Multipoint 
Distribution Service station in the 2596-2690 MHz frequency band is 
conditioned on the proffer to the affected ITFS station licensee of 
equipment capable of providing a ratio of 0 dB or more at no expense to 
the ITFS station licensee, and also conditioned, if necessary, on 
installation of such equipment, absent a showing by the affected ITFS 
station licensee demonstrating good cause and that the proposed 
equipment will not provide a ratio of 0 dB or more or that installation 
of such equipment, at no expense to the ITFS station licensee, is not 
possible.
    (3) For purposes of this section all interference calculations 
involving receive antenna performance shall use the reference antenna 
characteristics shown in figure 1.

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    (4) For purposes of this section, the received signal power level 
(RSL)dBW at the output of the FCC reference receiving antenna 
is obtained from the following formulas (or an equivalent adaptation):

(RSL)dBW=(EIRP)dBW-(LFS)dB+(G
AR)dB
where the free space loss (LFS) is
(LFS)dB=20 log (4d/)dB

in which the parameters are defined as follows:
    (RSL)dBW is the received power in decibels referenced to 
one watt.
    (EIRP)dBW is the equivalent isotropically radiated power 
in decibels above one watt.
    d is the distance of the signal path in meters.
     is the wavelength of the signal in meters.
    GAR is the dB gain of the reference receiving antenna 
above an isotropic antenna (obtained from Figure 1 of this section.)
    (5) A determination of signal path conditions shall use a 9.1 meters 
(30 feet) receiving antenna height, the transmitting antenna height, 
terrain elevation, and assume 4/3 earth radius propagation conditions.
    (6) An application will not be accepted for filing if cochannel or 
adjacent channel interference is predicted at the boundary of the 56.33 
km (35 mile) protected service area of an authorized or previously 
proposed incumbent station based on the following criteria:
    (i) Interference calculations shall be made only for directions 
where there is an unobstructed signal path from the site of a proposed 
station to the boundary of any protected area.
    (ii) Calculations of received power levels in units of dBW from the 
proposed station will be made at one degree intervals around the 
protected service area.
    (iii) The assumed value of the desired signal level at the boundary 
of an incumbent station shall be -83 dBW, which is the calculated 
received power in free space at a distance of 56.33 km (35 miles), given 
at EIRP of 2000 watts and a receiver antenna gain of 20 dBi.
    (iv) Harmful interference will be considered to occur at locations 
along the boundary wherever the ratio between the desired signal level 
of -83 dBw and the received power from a proposed cochannel or adjacent 
channel station is less than 45 dB or 0 dB for cochannel or adjacent 
channel proposals, respectively.
    (7) Alternatively, MDS applications will be accepted on the basis of 
an executed written interference agreement between potentially affected 
parties filed in accordance with Sec. 21.938.
    (g)(1) All interference studies prepared pursuant to paragraph (c) 
of this section must be served on all licensees, conditional licensees, 
and applicants for the stations required to be studied by this section. 
This service must include a copy of the FCC application and occur on or 
before the date the application is filed with the Commission.
    (2) MDS licensees, conditional licensees and applicants of 
facilities with 56.33 km (35 mile) protected service areas shall notify 
in writing the holders of authorizations for adjoining BTAs or PSAs of 
application filings for modified station licenses, provided the proposed 
facility would produce an unobstructed signal path to any location 
within the adjoining BTA or PSA. This service must include a copy of the 
FCC application and occur on or before the date the application is filed 
with the Commission.
    (h) For purposes of Sec. 21.31(a), an MDS application, except for 
those applications filed on or after September 15, 1995, filed for a 
facility that would cause harmful electrical interference within the 
protected service area of any authorized or previously proposed station 
will be presumed to be mutually exclusive with the application for such 
authorized or previously proposed station.
    (i)(1) For each application for a new station, or amendment thereto, 
or modification application, or amendment thereto, proposing Multipoint 
Distribution Service (MDS) facilities on the E, F, or H channels, filed 
on October 1, 1995, or thereafter, on or before the day the application 
or amendment is filed, the applicant must prepare, but is not required 
to submit with its application or amendment, an analysis demonstrating 
that operation of the MDS applicant's transmitter will not cause harmful 
electrical interference to each registered receive site of any

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existing D, E, F, or G channel Instructional Television Fixed Service 
station licensed, with a construct permit, or proposed in a pending 
application on the day such MDS application is filed, with an ITFS 
transmitter site within 50 miles of the coordinates of the MDS station's 
proposed transmitter site.
    (2) For each application described in paragraph (i)(1) of this 
section, the applicant must serve, by certified mail, return receipt 
requested, on or before the day the application or amendment described 
in paragraph (i)(1) of this section is initially filed with the 
Commission, a copy of the complete MDS application or amendment, 
including each exhibit and interference study, described in paragraph 
(i)(1) of this section, on each ITFS licensee, construction permittee, 
or applicant described in paragraph (i)(1) of this section.
    (3) For each application described in paragraph (i)(1) of this 
section, the applicant must certify and file, with the application or 
amendment, its certification of its compliance with the requirements of 
paragraph (i)(2) of this section.
    (4) For each application described in paragraph (i)(1) of this 
section, the applicant must file, on or before the 30th day after the 
application or amendment described in paragraph (i)(1) of this section 
is initially filed with the Commission, a written notice which contains 
the following:
    (i) Caption--ITFS Service Notice;
    (ii) Applicant's name, address, proposed service area and channel 
group, and application file number, if known;
    (iii) A list of each ITFS licensee and construction permittee 
described in paragraph (i)(1) of this section;
    (iv) The address of each ITFS licensee and construction permittee 
described in paragraph (i)(1) of this section used for service; and
    (v) A list of the date each ITFS licensee and construction permittee 
described in paragraph (i)(1) of this section received a copy of the 
complete application or amendment described in paragraph (i)(1) of this 
section, or a notation of lack of receipt by the ITFS licensee or 
construction permittee of a copy of the complete application or 
amendment, on or before such 30th day, together with a description of 
its efforts for receipt by each such licensee or construction permittee 
lacking receipt of the application.
    (5) The public notices described in paragraph (i)(6) of this section 
are as follows:
    (i) For initial applications for new MDS stations which participate 
in a lottery, this public notice is the notice announcing the selection 
of the applicant's application by lottery for qualification review.
    (ii) For initial applications for new MDS stations which participate 
in a competitive bidding process, this public notice is the notice 
announcing the application of the winning bidder in the competitive 
bidding process has been accepted for filing.
    (iii) For initial applications for new MDS stations which do not 
participate in a lottery or a competitive bidding process, this public 
notice is the notice announcing that the applicant's application is not 
mutually-exclusive with other MDS applications.
    (iv) For MDS modification applications, this public notice is the 
notice announcing that the modification application has been accepted 
for filing.
    (6)(i) Notwithstanding the provisions of Sections 1.824(c) and 
21.30(a)(4), for each application described in paragraph (i)(1) of this 
section, each ITFS licensee and each ITFS construction permittee 
described in paragraph (i)(1) of this section may file with the 
Commission on or before the 30th day after the public notice described 
in paragraph (i)(5) of this section, a petition to deny the MDS 
application.
    (ii) Except for the requirements as to the filing time deadline, 
this petition to deny must otherwise comply with the provisions of 
Section 21.30.
    (iii) In addition, this ITFS petition to deny must:
    (A) Identify the subject MDS application, including the applicant's 
name, station location, channel group, and application file number;
    (B) Include a certificate of service demonstrating service on the 
subject MDS applicant by certified mail, return receipt requested, on or 
before the 30th day after the MDS public notice described in paragraph 
(i)(5) of this section;

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    (C) Include a demonstration that it made efforts to reach agreement 
with the MDS applicant but was unable to do so;
    (D) Include an engineering analysis that operation of the proposed 
MDS station will cause harmful interference to its ITFS station;
    (E) Include a demonstration, in those cases in which the MDS 
applicant's analysis is dependent upon modification(s) to the ITFS 
facility, that the harmful interference cannot be avoided by the 
proposed substitution of new or modified equipment to be supplied and 
installed by the MDS applicant, at no expense to the ITFS licensee or 
construction permittee; and
    (F) Be limited to raising objections concerning the potential for 
harmful interference to its ITFS station or concerning a failure by the 
MDS applicant to serve the ITFS licensee or construction permittee with 
a copy of the complete application or amendment described in paragraph 
(i)(1) of this section.
    (iv) The Commission will presume an ITFS licensee or construction 
permittee described in paragraph (i)(1) of this section has no objection 
to operation of the MDS station, if the ITFS licensee or construction 
permittee fails to file a petition to deny by the deadline prescribed in 
paragraph (i)(6)(i) of this section.
    (j) If the initial application for facilities in the 2596-2644 
frequency band was filed on September 9, 1983, an applicant proposing to 
modify such facilities must include with its modification application:
    (1) An analysis demonstrating that the modification will not 
increase the size of the geographic area suffering harmful interference 
within the protected service area of existing or proposed co-channel or 
adjacent-channel facilities in the 2596-2644 MHz frequency band with a 
transmitter site within 80.5 km (50 miles) of the modifying station's 
transmitter site of the initial application for the interfered-with 
station was filed on September 9, 1983; and
    (2) An analysis demonstrating that the modification will not cause 
harmful interference to any new portion of the protected service area of 
existing or proposed co-channel or adjacent-channel facilities in the 
2596-2644 frequency band with a transmitter site within 80.5 km (50 
miles) of the modifying station's transmitter site, if the initial 
application for the interfered-with station was filed on September 9, 
1983.
    (k) If an initial application for facilities in the 2596-2644 
frequency band was filed on September 9, 1983, a licensee proposing to 
modify a constructed station may request exclusion from the interference 
analysis prescribed at Sec. 21.902(c) (1) and (2) with respect to 
another specified application for E or F channel facilities, if the 
modifying licensee files as part of its modification application a 
demonstration that:
    (1) The MDS application for which exclusion is requested was 
proposed by an initial application filed on September 9, 1983;
    (2) The MDS application for which exclusion is requested is not yet 
perfected by the submission of the information necessary for processing, 
as of the date of filing of the modification application; and
    (3) A copy of the licensee's modification application, including the 
demonstration specified in this paragraph, was served on the MDS 
applicant for which exclusion is requested, on or before the date of 
filing of the modification application.
[ 44 FR 60534 , Oct. 19, 1979, as amended at  48 FR 33901 , July 26, 1983; 
 49 FR 25479 , June 21, 1984;  52 FR 27556 , July 22, 1987;  55 FR 46010 , 
Oct. 31, 1990;  56 FR 57598 , Nov. 13, 1991;  56 FR 57818 , Nov. 14, 1991; 
 56 FR 65191 , Dec. 16, 1991;  58 FR 11798 , Mar. 1, 1993;  58 FR 44895 , Aug. 
25, 1993;  60 FR 36553 , July 17, 1995;  60 FR 36739 , July 18, 1995;  60 FR 57367 , Nov. 15, 1995;  61 FR 18098 , Apr. 24, 1996;  61 FR 26676 , May 28, 
1996]

    Effective Date Note:  At  61 FR 18098 , Apr. 24, 1996, Sec. 21.902 was 
amended by revising paragraphs (i)(1) and (i)(2). These paragraphs 
contain information collection and recordkeeping requirements and will 
not become effective until approval has been given by the Office of 
Management and Budget.