Mexican Border Zone Spacing
US FM station located within 320 km of the Mexican border has to meet Mexican border zone spacing requirements.
The table below lists spacing requirements for US FM stations with respect to Mexican stations based on FCC 73.207 rule.
| Relation | Co-Channel (Same Frequency) | 200 kHz (1st Adjacent Channel) | 400 or 600 kHz (2nd or 3rd Adjacent Channel) |
|---|---|---|---|
| A - A | 100 km | 61 km | 25 km |
| A - AA | 111 km | 68 km | 31 km |
| A - B1 | 138 km | 88 km | 48 km |
| A - B | 163 km | 105 km | 65 km |
| A - C1 | 196 km | 129 km | 74 km |
| A - C | 210 km | 161 km | 94 km |
| AA - AA | 115 km | 72 km | 31 km |
| AA - B1 | 143 km | 96 km | 48 km |
| AA - B | 178 km | 125 km | 69 km |
| AA - C1 | 200 km | 133 km | 75 km |
| AA - C | 226 km | 165 km | 95 km |
| B1 - B1 | 175 km | 114 km | 50 km |
| B1 - B | 211 km | 145 km | 71 km |
| B1 - B1 | 175 km | 114 km | 50 km |
| B1 - C1 | 233 km | 161 km | 77 km |
| B1 - C | 259 km | 193 km | 96 km |
| B - B | 237 km | 164 km | 65 km |
| B - C1 | 270 km | 195 km | 79 km |
| B - C | 270 km | 215 km | 98 km |
| C1 - C1 | 245 km | 177 km | 82 km |
| C1 - C | 270 km | 209 km | 102 km |
| C - C | 290 km | 228 km | 105 km |
Note
- US or Mexican Class A stations which have been notified internationally as Class A are limited to a maximum of 3.0 kW ERP at 100 meters HAAT.
- US or Mexican Class A stations which have been notified internationally as Class AA are limited to a maximum of 6.0 kW at 100 meters HAAT.
- US Class C3 assignments or allotments are considered Class B1.
- US Class C2 assignments or allotments are considered Class B.
- Class C1 assignments or allotments assume maximum facilities of 100 kW ERP at 300 meters HAAT. However, US Class C1 stations may not, in any event, exceed the domestic US limit of 100 kW ERP at 299 meters HAAT.
- US Class C0 assignments or allotments are considered Class C.
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