Adding a Second VHF Repeater Without License Modification
County A holds an FCC Part 90 license for a VHF high-band repeater on 155.715 MHz. The license authorizes one FB2 transmitter at Lookout Mountain at 50 W ERP, 12.5 kHz emission, and 500 mobiles. To close a dead zone, the county wants to place a second repeater 60 km northeast on the same frequency at 100 W ERP and simply program the same channel into all portable radios. The nearest co-channel licensee, County B, operates a repeater 85 km from the proposed site and has objected. County A's license expires in 14 months. A wildfire last summer prompted the request. County A has no frequency coordinator on staff and proposes to begin operation next month after installing the equipment.
1. May County A begin operating the second repeater under its existing license? Explain.
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No. The existing license authorizes one FB2 transmitter at Lookout Mountain at 50 W ERP. A second transmitter 60 km away, at 100 W ERP, on the same frequency is a major modification of the station authorization, not a radio-programming change. Operating before authorization would be unauthorized operation and could cause co-channel interference to County B. The fact that the license expires in 14 months does not create temporary authority; renewal is a separate filing and must be timely. Installing equipment does not confer operating authority.
2. What regulatory and technical steps should County A complete before operation?
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County A should engage an FCC-certified frequency coordinator for the VHF high-band. The modification application should include exact coordinates, antenna height above average terrain, ERP, antenna pattern, emission designator, and coverage contours. The coordinator should run co-channel and adjacent-channel spacing analysis against County B and other licensees, considering terrain and contour overlap.
Because County B objected, the coordinator may recommend a different frequency, lower power, a directional antenna, or a different site. CTCSS or DCS does not resolve co-channel contour overlap; it only reduces nuisance audio. County A should also verify that the 12.5 kHz emission designator and power are consistent with the narrowband plan. The license must be modified before operation, and the coordination record should be retained. If County A needs interim coverage, simplex tactical channels, cache radios, or a gateway may be used without adding an unauthorized fixed transmitter.
3. Under what circumstances, if any, could County A use a Special Temporary Authority (STA)?
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An STA is for a true emergency or other special temporary need, not for a planned dead-zone fix. If wildfire conditions create an imminent threat to life or property, County A could request an STA through the coordinator with a specific justification, duration, frequency, power, and geographic area. The STA would authorize only the parameters granted and only for the stated period. County A should not treat a seasonal wildfire risk as blanket authority to operate indefinitely. If an STA is denied or delayed, the county should use simplex, cache radios, or a gateway rather than operating the fixed repeater without authorization.