2
Advanced Protocols
Fig. 2 Peer-to-peer (unicast) vs. broadcast communication.
CODAN HF transceivers transmit on single side-
bands, either USB or LSB. This reduces the power
required to send HF signals and increases the
number of channels available within the HF spec-
trum. The transceivers are primarily used for long
distance communications. Obstructions such as
buildings and mountains have only little effect on
the communication. The HF radio waves propa-
gate in three ways simultaneously:
ground wave
,
direct wave
and
sky wave
. The ground wave trav-
els near the ground for short distances up to 100
km over land and 300 km over sea. The distance
covered depends on the channel frequency, trans-
mission power and environment. The direct wave
travels in a direct line from the transmitter to the
receiver. Finally, the sky wave is transmitted to-
ward the sky and is reflected by the ionosphere to
a distant receiver on earth.
Additionally, a handset and a speaker for acoustic
monitoring, can be connected to the transceiver.
The handset has buttons for
toggling mute on or off,
starting a call,
switching scanning on or off, or if the user
was in a call, ends the call and turns switch-
ing on,
manually tuning the antenna,
adjusting the receiver frequency to compen-
sate for any frequency difference between
the receiver and the transmitter,
selecting the mode (either USB or LSB),
selecting the channel frequency for the com-
munication.
CODAN HF Data Decoder
