Over-The-Horizon Radar is a military radar system deployed by the United States in various places outside the continental USA. In recent years, interference assumed to be from these systems has been widely noted in the shortwave pirate and amateur radio bands, primarily around the area of 7 MHz. The sound of these systems on typical shortwave receivers sounds like a loud, wideband chirping, and older listeners liken the sound to the Russian Woodpecker, a similar HF radar system of Soviet design.
Official WRC OTHR over the horizon radar bands
The allocations below 30 MHz are generally considered a fixed/mobile service - fixed service.
- 4.438 - 4.488 MHz 4438 kHz to 4488 kHz
- 5.250 - 5.275 MHz 5250 kHz to 5275 kHz
- 9.305 - 9.355 MHz 9305 kHz to 9355 kHz
- 13.450 - 13.550 MHz 13450 kHz to 13550 kHz (secondary allocation)
- 16.100 - 16.200 MHz 16100 kHz to 16200 kHz
- 24.450 - 24.650 MHz 24450 kHz to 24650 kHz
- 26.200 - 26.420 MHz 26200 kHz to 26420 kHz - 26 MHz portion of the 11 meter band, shared with other services, including paging and telemetry services, 26 MHz New Zealand 26.33 MHz - 26.77 MHz CB, freeband 11-meter CB operators, etc.
- 41.015 - 41.665 MHz 41015 kHz to 41665 kHz - may be allocated to additional land mobile, telemetry, or military tactical radio services
- 43.350 - 44.000 MHz 43350 kHz to 44000 kHz - may be allocated to land mobile, the Italian 43 MHz VHF FM "43 MHz CB" allocation, paging, telemetry or military tactical radio services
The 41.015 MHz to 41.665 MHz and 43.35 MHz to 44 MHz bands may be secondary depending on a specific country's radio allocations (as they are both above 30 MHz and considered VHF bands).
The 41.015 MHz to 44 MHz band is allocated to the fixed/mobile service on an international basis.
In the United States, the band is allocated to several VHF low sub-bands:
- 40.00 MHz - 42.00 MHz Military land mobile, fixed, Government land mobile, fixed, fixed/mobile
- 42.00 MHz - 42.95 MHz Land Mobile - Public Safety, Government land mobile, military land mobile
- 42.95 MHz - 43.19 MHz Land Mobile - Business Radio Service, military land mobile
- 43.19 MHz - 43.69 MHz Land Mobile - Public Safety, Military land mobile, Business Radio Service
- 43.69 MHz - 44.61 MHz Land Mobile - Business Radio Service, military land mobile
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