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:
Table 2-Maximum Rearward Effective Radiated Power Allowed for Shore Stations; Rearward Effective Radiated Power (in Watts) From Shore Antenna in a Sector [LESS THAN]±[GREATER THAN]221/2° 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 [LESS THAN]±[GREATER THAN]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).
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 |
47 C.F.R. §90.315