Sec.  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  Sec. 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  Sec. 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]