Manpack Transceiver 2110 series Getting Started Guide 69
CODAN
Appendix E—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
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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