§ 25.203   Choice of sites and frequencies.

   (a) Sites and frequencies for earth stations, other than ESVs, operating in
   frequency bands shared with equal rights between terrestrial and space
   services, shall be selected, to the extent practicable, in areas where the
   surrounding terrain and existing frequency usage are such as to minimize the
   possibility of harmful interference between the sharing services.

   (b) An applicant for an earth station authorization, other than an ESV, in a
   frequency band shared with equal rights with terrestrial microwave services
   shall compute the great circle coordination distance contour(s) for the
   proposed station in accordance with the procedures set forth in § 25.251. The
   applicant  shall  submit  with  the application a map or maps drawn to
   appropriate scale and in a form suitable for reproduction indicating the
   location of the proposed station and these contours. These maps, together
   with the pertinent data on which the computation of these contours is based,
   including all relevant transmitting and/or receiving parameters of the
   proposed  station  that  is  necessary  in assessing the likelihood of
   interference, an appropriately scaled plot of the elevation of the local
   horizon as a function of azimuth, and the electrical characteristics of the
   earth station antenna(s), shall be submitted by the applicant in a single
   exhibit to the application. The coordination distance contour plot(s),
   horizon elevation plot, and antenna horizon gain plot(s) required by this
   section may also be submitted in tabular numerical format at 5° azimuthal
   increments instead of graphical format. At a minimum, this exhibit shall
   include the information listed in paragraph (c)(2) of this section. An earth
   station applicant shall also include in the application relevant technical
   details (both theoretical calculations and/or actual measurements) of any
   special  techniques,  such as the use of artificial site shielding, or
   operating procedures or restrictions at the proposed earth station which are
   to  be  employed  to  reduce the likelihood of interference, or of any
   particular characteristics of the earth station site which could have an
   effect on the calculation of the coordination distance.

   (c) Prior to the filing of its application, an applicant for operation of an
   earth  station,  other than an ESV, VMES or ESAA, shall coordinate the
   proposed frequency usage with existing terrestrial users and with applicants
   for terrestrial station authorizations with previously filed applications in
   accordance with the following procedure:

   (1)  An  applicant for an earth station authorization shall perform an
   interference analysis in accordance with the procedures set forth in § 25.251
   for each terrestrial station, for which a license or construction permit has
   been granted or for which an application has been accepted for filing, which
   is  or  is to be operated in a shared frequency band to be used by the
   proposed  earth  station  and which is located within the great circle
   coordination distance contour(s) of the proposed earth station.

   (2) The earth station applicant shall provide each such terrestrial station
   licensee, permittee, and prior filed applicant with the technical details of
   the proposed earth station and the relevant interference analyses that were
   made.  At  a  minimum,  the  earth station applicant shall provide the
   terrestrial user with the following technical information:

   (i) The geographical coordinates of the proposed earth station antenna(s),

   (ii) Proposed operating frequency band(s) and emission(s),

   (iii) Antenna center height above ground and ground elevation above mean sea
   level,

   (iv) Antenna gain pattern(s) in the plane of the main beam,

   (v) Longitude range of geostationary satellite orbit (GSO) satellites at
   which  antenna  may  be pointed, for proposed earth station antenna(s)
   accessing GSO satellites,

   (vi) Horizon elevation plot,

   (vii) Antenna horizon gain plot(s) determined in accordance with § 25.251 for
   satellite longitude range specified in paragraph (c)(2)(v) of this section,
   taking into account the provisions of § 25.251 for earth stations operating
   with non-geostationary satellites,

   (viii) Minimum elevation angle,

   (ix) Maximum equivalent isotropically radiated power (e.i.r.p.) density in
   the main beam in any 4 kHz band, (dBW/4 kHz) for frequency bands below 15
   GHz or in any 1 MHz band (dBW/MHz) for frequency band above 15 GHz,

   (x) Maximum available RF transmit power density in any 1 MHz band and in any
   4 kHz band at the input terminals of the antenna(s),

   (xi)  Maximum permissible RF interference power level as determined in
   accordance with § 25.251 for all applicable percentages of time, and

   (xii) A plot of great circle coordination distance contour(s) and rain
   scatter coordination distance contour(s) as determined by § 25.251.

   (3) The coordination procedures specified in § 101.103 of this chapter and
   § 25.251 shall be applicable except that the information to be provided shall
   be that set forth in paragraph (c)(2) of this section, and that the 30-day
   period allowed for response to a request for coordination may be increased
   to a maximum of 45 days by mutual consent of the parties.

   (4) Where technical problems are resolved by an agreement or operating
   arrangement between the parties that would require special procedures be
   taken to reduce the likelihood of harmful interference (such as the use of
   artificial site shielding) or would result in lessened quality or capacity
   of either system, the details thereof shall be contained in the application.

   (5) The Commission may, in the course of examining any application, require
   the submission of additional showings, complete with pertinent data and
   calculations in accordance with § 25.251, showing that harmful interference
   is not likely to result from the proposed operation.

   (d) An applicant for operation of an earth station, other than an ESV, VMES
   or an ESAA, shall also ascertain whether the great circle coordination
   distance contours and rain scatter coordination distance contours, computed
   for those values of parameters indicated in § 25.251 (Appendix 7 of the ITU
   RR)  for  international  coordination, cross the boundaries of another
   Administration. In this case, the applicant shall furnish the Commission
   copies of these contours on maps drawn to appropriate scale for use by the
   Commission in effecting coordination of the proposed earth station with the
   Administration(s) affected.

   (e) Protection for Table Mountain Radio Receiving Zone, Boulder County,
   Colorado.

   (1) Applicants for a station authorization to operate in the vicinity of
   Boulder  County,  Colorado  under  this  part  are advised to give due
   consideration, prior to filing applications, to the need to protect the
   Table Mountain Radio Receiving Zone from harmful interference. These are the
   research  laboratories  of the Department of Commerce, Boulder County,
   Colorado. To prevent degradation of the present ambient radio signal level
   at the site, the Department of Commerce seeks to ensure that the field
   strengths of any radiated signals (excluding reflected signals) received on
   this 1800 acre site (in the vicinity of coordinates 40°07′50″ N Latitude,
   105°14′40″ W Longitude) resulting from new assignments (other than mobile
   stations) or from the modification or relocation of existing facilities do
   not exceed the following values:
   Frequency range         In authorized bandwidth of service
                   Field strength (mV/m) Power flux density^1 (dBW/m^2)
   Below 540 kHz                      10                          −65.8
   540 to 1600 kHz                    20                          −59.8
   1.6 to 470 MHz                     10                        ^2−65.8
   470 to 890 MHz                     30                        ^2−56.2
   Above 890 MHz                       1                        ^2−85.8

   ^1Equivalent values of power flux density are calculated assuming free space
   characteristic impedance of 376.7 = 120Ï€ ohms.

   ^2Space stations shall conform to the power flux density limits at the
   earth's surface specified in appropriate parts of the FCC rules, but in no
   case should exceed the above levels in any 4 kHz band for all angles of
   arrival.

   (2) Advance consultation is recommended particularly for those applicants
   who have no reliable data which indicates whether the field strength or
   power flux density figures in the above table would be exceeded by their
   proposed radio facilities (except mobile stations). In such instances, the
   following is a suggested guide for determining whether coordination is
   recommended:

   (i) All stations within 2.5 kilometers;

   (ii) Stations within 5 kilometers with 50 watts or more average effective
   radiated power (ERP) in the primary plane of polarization in the azimuthal
   direction of the Table Mountain Radio Receiving Zone;

   (iii) Stations within 15 kilometers with 1 kW or more average ERP in the
   primary plane of polarization in the azimuthal direction of Table Mountain
   Receiving Zone;

   (iv) Stations within 80 kilometers with 25 kW or more average ERP in the
   primary plane of polarization in the azimuthal direction of Table Mountain
   Receiving Zone.

   (3) Applicants concerned are urged to communicate with the Radio Frequency
   Management Coordinator, Department of Commerce, Research Support Services,
   NOAA  R/E5X2, Boulder Laboratories, Boulder, CO 80303; telephone (303)
   497-6548, in advance of filing their applications with the Commission.

   (4) The Commission will not screen applications to determine whether advance
   consultation has taken place. However, applicants are advised that such
   consultation  can  avoid objections from the Department of Commerce or
   proceedings to modify any authorization which may be granted which, in fact,
   delivers a signal at the site in excess of the field strength specified
   herein.

   (f) Notification to the National Radio Astronomy Observatory: In order to
   minimize possible harmful interference at the National Radio Astronomy
   Observatory site at Green Bank, Pocahontas County, W. Va., and at the Naval
   Radio Research Observatory site at Sugar Grove, Pendleton County, W. Va.,
   any applicant for operating authority under this part for a new station,
   other than a mobile or temporary fixed station, within the area bounded by
   39°15′ N. on the north, 78°30′ W. on the east, 37°30′ N. on the south and
   80°30′ W. on the west or for modification of an existing license for such
   station  to  change  the station's frequency, power, antenna height or
   directivity,  or  location  must, when filing the application with the
   Commission, simultaneously notify the Director, National Radio Astronomy
   Observatory, P.O. Box No. 2, Green Bank, W. Va. 24944, in writing, of the
   technical particulars of the proposed station. Such notification shall
   include the geographical coordinates of the antenna, antenna height, antenna
   directivity if any, proposed frequency, type of emission, and power. In
   addition, the applicant shall indicate in his application to the Commission
   the date notification was made to the observatory. After receipt of such
   applications, the Commission will allow a period of 20 days for comments or
   objections in response to the notifications indicated. If an objection to
   the  proposed  operation is received during the 20-day period from the
   National Radio Astronomy Observatory for itself or on behalf of the Naval
   Radio Research Observatory, the Commission will consider all aspects of the
   problem and take whatever action is deemed appropriate.

   (g) Protection for Federal Communications Commission monitoring stations:

   (1) Applicants in the vicinity of an FCC monitoring station for a radio
   station authorization to operate new transmitting facilities or changed
   transmitting facilities which would increase the field strength produced
   over the monitoring station over that previously authorized are advised to
   give consideration, prior to filing applications, to the possible need to
   protect the FCC stations from harmful interference. Geographical coordinates
   of the facilities which require protection are listed in § 0.121(c) of the
   Commission's Rules. Applications for stations (except mobile stations) which
   will produce on any frequency a direct wave fundamental field strength of
   greater than 10 mV/m in the authorized bandwidth of service (−65.8 dBW/m2
   power flux density assuming a free space characteristic impedance of 120
   ohms) at the referenced coordinates, may be examined to determine extent of
   possible interference. Depending on the theoretical field strength value and
   existing root-sum-square or other ambient radio field signal levels at the
   indicated coordinates, a clause protecting the monitoring station may be
   added to the station authorization.

   (2) In the event that the calculated value of the expected field strength
   exceeds 10 mV/m (−65.8 dBW/m2) at the reference coordinates, or if there is
   any question whether field strength levels might exceed the threshold value,
   advance consultation with the FCC to discuss any protection necessary should
   be considered. See § 0.401 of this chapter for contact information.

   (3) Advance consultation is suggested particularly for those applicants who
   have no reliable data which indicates whether the field strength or power
   flux density figure indicated would be exceeded by their proposed radio
   facilities (except mobile stations). In such instances, the following is a
   suggested guide for determining whether an applicant should coordinate:

   (i) All stations within 2.5 kilometers;

   (ii) Stations within 5 kilometers with 50 watts or more average effective
   radiated power (ERP) in the primary plane of polarization in the azimuthal
   direction of the Monitoring Station;

   (iii) Stations within 15 kilometers with 1 kW or more average ERP in the
   primary plane of polarization in the azimuthal direction of the Monitoring
   Station;

   (iv) Stations within 80 kilometers with 25 kW or more average ERP in the
   primary plane of polarization in the azimuthal direction of the Monitoring
   Station.

   (4)  Advance  coordination  for  stations  operating above 1000 MHz is
   recommended  only  where  the proposed station is in the vicinity of a
   monitoring  station  designated  as a satellite monitoring facility in
   § 0.121(c) of this chapter and also meets the criteria outlined in paragraphs
   (g)(2) and (3) of this section.

   (5) The Commission will not screen applications to determine whether advance
   consultation has taken place. However, applicants are advised that such
   consultation can avoid objections from the Federal Communications Commission
   or modification of any authorization which will cause harmful interference.

   (h) Sites and frequencies for GSO and NGSO earth stations, operating in a
   frequency band where both have a co-primary allocation, shall be selected to
   avoid earth station antenna mainlobe-to-satellite antenna mainlobe coupling,
   between NGSO systems and between NGSO and GSO systems, in order to minimize
   the possibility of harmful interference between these services. Prior to
   filing an earth station application, in bands with co-primary allocations to
   NGSO and GSO earth stations, the applicant shall coordinate the proposed
   site and frequency usage with existing earth station licensees and with
   current earth station authorization applicants.

   (i) Any applicant for a new permanent transmitting fixed earth station to be
   located on the island of Puerto Rico, Desecheo, Mona, Vieques, or Culebra,
   or for modification of an existing authorization to change the frequency,
   power, antenna height, directivity, or location of such a station on one of
   these  islands  in a way that would increase the likelihood of causing
   interference, must notify the Interference Office, Arecibo Observatory, HC3
   Box 53995, Arecibo, Puerto Rico 00612, in writing or electronically, of the
   technical  parameters  of the proposal. Applicants may wish to consult
   interference guidelines, which will be provided by Cornell University.
   Applicants who choose to transmit information electronically should e-mail
   to: prcz@naic.edu.

   (1) The notification to the Interference Office, Arecibo Observatory shall
   be made prior to, or simultaneously with, the filing of the application with
   the Commission. The notification must specify the geographical coordinates
   of the antenna (NAD-83 datum), antenna height above ground, ground elevation
   at the antenna, antenna directivity and gain, proposed frequency, relevant
   FCC rule part, type of emission, effective radiated power, and whether the
   proposed use is itinerant. Generally, submission of the information in the
   technical portion of the FCC license application is adequate notification.
   In  addition,  the  applicant shall indicate in its application to the
   Commission the date notification was made to the Arecibo Observatory.

   (2)  After receipt of such applications, the Commission will allow the
   Arecibo  Observatory a period of 20 days for comments or objections in
   response to the notification indicated. The applicant will be required to
   make  reasonable efforts in order to resolve or mitigate any potential
   interference problem with the Arecibo Observatory and to file either an
   amendment to the application or a modification application, as appropriate.
   If  the  Commission  determines  that  an  applicant has satisfied its
   responsibility to make reasonable efforts to protect the Observatory from
   interference, its application may be granted.

   (3)  The  provisions of this paragraph do not apply to operations that
   transmit on frequencies above 15 GHz.

   (j)  Applicants  for  non-geostationary  1.6/2.4  GHz Mobile-Satellite
   Service/Radiodetermination-Satellite Service feeder links in the 17.7-20.2
   GHz and 27.5-30.0 GHz bands shall indicate the frequencies and spacecraft
   antenna gain contours towards each feeder-link earth station location and
   will  coordinate  with  licensees of other Fixed-Satellite Service and
   terrestrial-service  systems  sharing the band to determine geographic
   protection   areas   around  each  non-geostationary  Mobile-Satellite
   Service/Radiodetermination-Satellite Service feeder-link earth station.

   (k) An applicant for operation of an earth station, other than an ESV, VMES
   or  an  ESAA,  that  will  operate  with  a geostationary satellite or
   non-geostationary  satellite  in  a shared frequency band in which the
   non-geostationary system is (or is proposed to be) licensed for feeder
   links, shall demonstrate in its applications that its proposed earth station
   will not cause unacceptable interference to any other satellite network that
   is authorized to operate in the same frequency band, or certify that the
   operations of its earth station shall conform to established coordination
   agreements between the operator(s) of the space station(s) with which the
   earth station is to communicate and the operator(s) of any other space
   station licensed to use the band.

   (l) Applicants for feeder link earth station facilities operating in the
   25.05-25.25  GHz  band may be licensed only in Economic Areas where no
   existing  FS  licensee has been authorized, and shall coordinate their
   operations with 24 GHz fixed service operations if the power flux density of
   their transmitted signal at the boundary of the fixed service license area
   is equal to or greater than −114 dBW/m2 in any 1 MHz.

   (1)  When  uplink  adaptive  power  control is used, the EIRP used for
   calculation of the power flux density level should be the maximum possible,
   taking into account the adaptive power increase.

   (2) The power flux density levels should be calculated based on the actual
   off-axis gain characteristics of the earth station antenna, and should
   assume free space propagation conditions.

   (3) When determining whether the power flux density threshold limit is
   exceeded at the 24 GHz FS licensing boundary, a feeder link earth station
   applicant must take into account not only the transmissions from its own
   antenna(s), but also those from any previously authorized feeder link earth
   stations. Thus, if the cumulative power flux density level at the FS license
   boundary is in excess of −114 dBW/m2/MHz, the earth station applicant must
   either modify its proposed operations such that this value is not exceeded,
   or enter into coordination with the affected FS licensee.

   [ 30 FR 7176 , May 28, 1965]

   Editorial Note: For Federal Register citations affecting § 25.203, see the
   List of CFR Sections Affected, which appears in the Finding Aids section of
   the printed volume and at www.fdsys.gov.

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