§ 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 5DEG
   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 40DEG07'50'' N Latitude, 105DEG14'40'' 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=120p 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 39DEG15' N. on the north, 78DEG30'
   W. on the east, 37DEG30' N. on the south and 80DEG30' 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.

   return arrow Back to Top