§  90.315   Special provisions governing use of frequencies in the 476–494 MHz
band (TV Channels 15, 16, 17) in the Southern Louisiana-Texas Offshore Zone.

   (a) The frequency bands from 490–491 and 493–494 MHz will be available
   for assignment to stations governed by this part within Zone A. The
   boundaries of Zone A are from longitude 87°45' on the east to longitude
   94°00' on the west, and from the 3-mile limit along the Gulf of Mexico
   shoreline on the north to the limit of the Outer Continental Shelf on
   the south. The frequency bands from 484–485 and 476–488 MHz will be
   available for assignment to stations governed by this part within Zone
   B. The boundaries of Zone B are from longitude 87°45' on the east to
   longitude 95°00' on the west and from the 3-mile limit along the Gulf
   of Mexico shoreline on the north to the limit of the Outer Continental
   Shelf on the south. The frequency bands from 478–479 and 481–481 MHz
   will be available for assignment to stations governed by this part
   within Zone C. The boundaries of Zone C are from longitude 94°00' on
   the east, the 3-mile limit on the north and west, a 281 km (175 mile)
   radius from the reference point at Linares, N.L., Mexico on the
   southwest, latitude 26°00' on the south, and the limits of the Outer
   Continental Shelf on the southeast. These frequencies may also be
   assigned to fixed stations located on shore designed to provide
   communications service within the zone.

   (b) Offshore base/mobile, and offshore and shore fixed stations may be
   authorized.

   (c) F2, F3, F4, F9, and A2, A3, A4, and A9 emissions may be authorized.

   (d) Offshore stations shall afford cochannel protection to TV stations
   on Channels 15, 16 and 17. Station operating parameters shall be in
   accordance with the values given in table 1 of this section.

   Table 1—Protection of Cochannel Television Stations by Offshore
   Stations Operating in the Southern Louisiana-Texas Offshore Zone (65 dB
   Protection); Maximum Effective Radiated Power

   [In Watts]
   Distance from transmitter to co-channel TV station kilometers (miles)
   Antenna Height above sea level meters (feet)
   30.5 (100) 45 (150) 61 (200)
   338 (210) 1,000 1,000 1,000
   330 (205) 1,000 900 800
   322 (200) 800 710 630
   314 (195) 590 520 450
   306 (190) 450 400 330
   298 (185) 320 280 240
   290 (180) 250 210 175
   281 (175) 175 150 130
   274 (170) 130 110 100
   265 (165) 95 80 70
   257 (160) 65 55 50
   249 (155) 50 40 35
   241 (150) 35 30 25

   Note: To determine the maximum permissible effective radiated power:

   (1) As specified in § 73.611 determine the distance between the proposed
   station and the cochannel television station. If the exact distance
   does not appear in table 1 of this section, the next lower distance
   separation is to be used.

   (2) Opposite this distance figure ERPs are given that may be used for
   antenna heights of 30.5, 45 or 61 meters (100, 150 or 200 ft) ASL. If
   the exact antenna height is not shown, the ERP allowed will be that
   shown for the next higher antenna height.

   (e) Shore stations communicating point-to-point with offshore stations
   will be permitted at least the same ERP as the offshore station, but
   only in the direction of the offshore station. A directional antenna
   shall be used and the rearward radiated power from the antenna in a
   sector ±221/2° from the line joining the shore antenna to the cochannel
   television station shall not exceed those shown in table 2 of this
   section.

   Table 2—Maximum Rearward Effective Radiated Power Allowed for Shore
   Stations; Rearward Effective Radiated Power (in Watts) From Shore
   Antenna in a Sector <±>22 1/2° From the Line Joining the Shore Antenna
   to the Cochannel Television Station
   Distance from transmitter to cochannel television station: kilometers
   (miles) Antenna height above ground in meters (feet)
   30.5 (100) 45 (150) 61 (200) 91.5 (300) 152.5 (500) 228 (750)
   298 (185) 320 280 240 190 125 90
   290 (180) 250 210 175 125 100 60
   281 (175) 175 150 130 100 70 50
   274 (170) 130 110 100 75 40 35
   265 (165) 95 82 70 50 35 25
   257 (160) 65 55 50 40 25 20
   249 (155) 50 40 35 30 20 15
   241 (150) 35 30 25 20 15 10
   233 (145) 25 20 18 15 10 7
   225 (140) 18 15 13 10 7 5
   217 (135) 13 10 9 7 5 3
   209 (130) 10 8 6 5 3 2
   201 (125) 7 6 5 4 3 2
   193 (120) 5 4 3 3 2 1

   Note: As an example of the use of tables 1 and 2, assume an offshore
   station located 290 km (180 mi) from TV Channel 17 located in Bude,
   Miss. with an antenna height of 30.5 m (100 ft). Table 1 allows this
   station to operate with 250 W ERP. Now assume the shore station
   communicating with the offshore station is 48 km (30 mi) from the
   offshore station and 241 km (150 mi) from Bude, Miss. The shore station
   antenna height is 152.5 m (500 ft) above ground. The shore station will
   be allowed the same ERP as the offshore station (250 W) in the
   direction of the offshore station. Table 2 indicates that the effective
   radiated power in a sector <±> 221/2° from the line joining the shore
   antenna to Bude, Miss. can only be 15 W. Consequently, a directional
   antenna must be used whose minimum front-to-back ratio over this 45°
   sector must be at least 12.2 dB. (250 W forward power to 15 W rearward
   power is a power ratio of 16.6 or 12.2 dB).

   (f) To provide cochannel protection to television stations, no shore
   station will be allowed closer than 193 km miles) from the cochannel
   television station.

   (g) To provide adjacent channel protection to television stations, no
   shore or offshore station shall be allowed within 128 kilometers (80
   miles) of the adjacent channel television station.

   (h) Mobile stations shall not operate closer to shore than 6.4 km (4
   miles) beyond the three mile limit and shall not operate with an ERP in
   excess of 100 watts with 9.1 m (30 ft) maximum antenna height.

   (i) Mobile stations installed in aircraft shall operate 11 km (7 miles)
   beyond the three mile limit and shall not operate with an ERP in excess
   of 1 watt or at heights in excess of 305 m (1000 feet) AMSL.

   (j)(1) The following frequency bands are available for assignment in
   all services for use in the Zones defined in paragraph (a) of this
   section.

   Paired Frequencies (MHz)
   Zone Transmit (or receive) Receive (or transmit)
   A      490.01875–490.98125   493.01875–493.98125
   B      484.01875–484.98125   487.01875–487.98125
   C      478.01875–478.98125   481.01875–481.98125

   (2) Only the first and last assignable frequencies are shown.
   Frequencies shall be assigned in pairs with 3 MHz spacing between
   transmit and receive frequencies. Assignable frequency pairs will occur
   in increments of 6.25 kHz. The following frequencies will be assigned
   for a maximum authorized bandwidth of 6 kHz: 478.01875, 478.98125,
   484.01875, 484.98125, 490.01875, 490.98125, 481.01875, 481.98125,
   487.01875, 487.98125, 493.01875, and 493.98125 MHz.

   (k) Fixed stations operating point-to-point shall be assigned
   frequencies beginning with 490.025/493.025 MHz (Zone A),
   484.025/487.025 MHz (Zone B) and 478.025–481.025 MHz (Zone C) and
   progressing upwards utilizing available frequencies toward the end of
   the band. Offshore base/mobile stations shall be assigned frequencies
   beginning at 490.975/493.975 MHz (Zone A), 484.975/478.975 MHz (Zone B)
   and 478.975/481.975 MHz (Zone C) and progressing downwards utilizing
   available frequencies toward the beginning of the band. All frequency
   assignments are subject to the conditions specified in § 90.173.

   [ 50 FR 12027 , Mar. 27, 1985;  50 FR 14389 , Apr. 12, 1985, as amended at
    58 FR 44959 , Aug. 25, 1993;  60 FR 37277 , July 19, 1995;  72 FR 35198 ,
   June 27, 2007]