Sec. 25.203  Choice of sites and frequencies.

    (a) Sites and frequencies for earth stations, 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 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 
Sec. Sec. 25.251 through 25.253 and the rain scatter coordination 
distance contour(s) for the proposed station in accordance with the 
procedures set forth in Sec. 25.254. 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 might be useful 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 deg. 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 his application, an earth station 
applicant 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 
Sec. 25.255 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,

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    (v) Longitude range of geostationary satellites at which antenna may 
be pointed,
    (vi) Horizon elevation plot,
    (vii) Antenna horizon gain plot(s) determined in accordance with 
Sec. 25.253(b) for satellite longitude range specified in paragraph 
(c)(2)(v) of this section, taking into account the provisions of 
Sec. 25.253(a)(2) for earth stations operating with non-geostationary 
satellites.
    (viii) Minimum elevation angle,
    (ix) Maximum effective isotropically radiated power (EIRP) in any 4 
kHz band in the main beam, (dBW/4 kHz),
    (x) Maximum available RF transmit power 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 Sec. 25.252 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 
Secs. 25.253 and 25.254.
    (3) The coordination procedure specified in Sec. 21.100(d) of this 
chapter 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 Sec. Sec. 251.251 through 
25.256, showing that harmful interference is not likely to result from 
the proposed operation.
    (d) An applicant for an earth station authorization shall also 
ascertain whether the great circle coordination distance contours and 
rain scatter coordination distance contours, computed for those values 
of parameters indicated in table 1 of Sec. 25.252 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 deg. 07' 50' N Latitude, 105 deg. 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:

                                                                        
------------------------------------------------------------------------
                                                 In authorized bandwidth
                                                       of service       
                                               -------------------------
                Frequency range                    Field      Power flux
                                                  strength     density1 
                                                   (mV/m)     (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
------------------------------------------------------------------------
\1\ Equivalent values of power flux density are calculated assuming free
  space characteristic impedance of 376.7=120 ohms.            
\2\ Space 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

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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 located 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 a station authorization other 
than mobile, temporary base, temporary fixed, Personal Radio, Civil Air 
Patrol, or amateur seeking a station license for a new station, a 
construction permit to construct a new station or to modify an existing 
station license in a manner which would change either the frequency, 
power, antenna height or directivity, or location of such a station 
within the area bounded by 39 deg.15' N. on the north, 78 deg.30' W. on 
the east, 37 deg.30' N. on the south and 80 deg.30' W. on the west 
shall, at the time of filing such 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 Sec. 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

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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 calculated value of expected field 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. Prospective applicants may communicate 
with: Chief, Compliance and Information Bureau, Federal Communications 
Commission, Washington, DC 20554, Telephone (202) 632-6980.
    (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 
Sec. 0.121(c) of the Commission's Rules and also meets the criteria 
outlined in paragraphs (h)(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) [Reserved]
    (j) Applicants for non-geostationary 1.6/2.4 GHz Mobile-Satellite 
Service/ Radiodetermination satellite service feeder links in the bands 
17.7-20.2 GHz and 27.5-30.0 GHz 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 an earth station 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

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the operator(s) of any other space station licensed to use the band.
[ 30 FR 7176 , May 28, 1965, as amended at  36 FR 2562 , Feb. 6, 1971;  38 FR 8573 , Apr. 4, 1973;  42 FR 8329 , Feb. 9, 1977;  44 FR 77167 , Dec. 31, 
1979;  50 FR 40862 , Oct. 7, 1985;  58 FR 13419 , Mar. 11, 1993;  58 FR 44904 , Aug. 25, 1993;  59 FR 53329 , Oct. 21, 1994;  61 FR 8477 , Mar. 5, 
1996;  61 FR 9945 , Mar. 12, 1996;  61 FR 44181 , Aug. 28, 1996]