The five configurations are:
a. Radio
Terminal.
Radio
terminals
are
complete
radio
transmitting
and
receiving
units,
including
the
radio
sets,
multiplexing equipment, and a power generating source.
A
radio
system consists of at least two radio terminals.
b. Cable Terminal.
Cable terminals are used in place of radio
terminals when the tactical situation and the siting opportunities
permit or dictate using cable communications systems. Again, a cable
system consists of at least two cable terminals.
c. Radio Relay. Radio relays or repeators are used to extend the
range or negotiate obstacles when employing radio systems. The radio
relay receives the signal from the transmitting radio terminal, and
retransmits the signal to the next relay station or to the receiving
radio terminal.
Figure 1-18 shows a radio system employing a radio
relay.
d. Cable Relay.
Cable or radio systems may also employ cable
relays.
As with radio systems, cable systems are limited in their
range, and require relays to extend their range. Figure 1-19 shows a
radio system using a cable link in the repeater station. Figure 1-21
(page 1-26) shows a cable system using a cable repeater station.
e. Radio/Cable Conversion. When you use a cable link in a radio
system as a repeating or a radio link in a cable system, you must use
an interface to condition the signal of one medium to be useful for
the other medium.
Note that the cable link in figure 1-19 uses a
radio set to receive the transmitted signal.
The interface unit
conditions the signal to conduct it across the cable link.
The
signal is then reconditioned to retransmit it across the radio span
to the receive radio terminal.
Basically, a multichannel radio system consists of a series of radio
sets operating in tandem on frequencies above 30 MHz.
By adding
multiplexing, a multichannel system provides communications channel
capability for telephone, teletype, facsimile, and data.
A multichannel radio system must have at least two terminals, one at
each end of the system. Many factors determine the maximum distance
between terminals.
We discuss those factors in detail in lesson 2.
When necessary, radio relay sites relay the signal to the next site.
Generally, the useful transmission limit is 40 to 48 km (25 to 30
miles). Beyond this range, even with no obstructions, the curvature
of the earth interferes with establishing a path between the
transmitter and receiver.
1-23
SS0016
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