HF RADIO TRANSMISSION
HF RADIO TRANSMISSION
426 ENVOY™ TRANSCEIVER REFERENCE MANUAL
HF radio transmission
The HF band is the range of frequencies between 3 and 30 MHz. HF transceivers
usually cover a frequency range of 1.6 to 30 MHz.
Codan HF transceivers transmit on single sidebands. This reduces the power required
to send HF signals, and increases the number of channels available within the HF
spectrum.
HF transceivers are primarily used for long-range communication where distances of
3000 km (1800 mi) and more are possible. Obstructions such as buildings and
mountains have little effect on long-range communication. HF radio can cover such
large distances because of the way the transmitted radio signal propagates.
HF radio waves propagate in three ways simultaneously:
• ground wave
• direct wave
• sky wave
Related links:
Ground wave on page 426
Direct wave on page 426
Sky wave on page 427
Ground wave
The ground wave travels near the ground for short distances, typically up to 100 km
(60 mi) over land and 300 km (190 mi) over sea. The distance covered depends upon
the operating frequency, transmission power and type of terrain.
Direct wave
The direct wave travels in a direct line-of-sight from the transmitter to the receiver.
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