The HF Band (3 MHz-30 MHz)
The HF band is favored by the military and other specialized Government agencies because of reliability and vast coverage capabilities. HF has a number of technical advantages over higher frequencies that are used commercially:
- Skip Capability– Whereas UHF, VHF and microwave frequencies offer only line of sight communication, normally less than 40 miles, HF frequencies offer both local communications through ground waves and long-range communications by reflecting off of the ionosphere. Single HF hops (reflections) provide links from 400 miles to 2000 miles, while multiple hops communicate around the world.
- Lower attenuation – Commercial frequencies tend to suffer from “propagation attenuation” in which the atmosphere, rain, foliage and terrain dissipate the signal. HF, on the other hand, is virtually unaffected by such “obstructions”.
- Low power – HF transmitters can operate over long distances and be effective at low power without the need for repeaters.
- Secure – HySky’s low power transmissions are difficult to discern from background atmospheric noise, which makes reception very difficult without technology similar to our extremely sensitive receivers and large antenna arrays that are located in remote, low-noise rural areas.
Factors such as range, antenna efficiency and atmospheric noise affect the frequency spectrum available for communications transmissions at any given time. Notwithstanding, HySky has found that the HF band of frequencies offers the best compromise when clients require a secure system that operates with low power and covers vast areas.