22
UNDERSTANDING REPEATERS
Operating through a repeater, where you transmit on one fre-
quency and receive on another, is called
duplex
operation. Oper-
ating direct to another station, where you transmit and receive on
the same frequency, is called
simplex
operation.
A repeater is a station that receives a signal on one frequency
(the
input
frequency) and then retransmits that signal on a differ-
ent frequency (the
output
frequency). Repeater antennas are typ-
ically located at the tops of tall buildings or on antenna towers, so
a relatively low-power signal can reach the repeater. The repeat-
er retransmits the signal at a higher power. This gives your trans-
ceiver the ability to communicate over a much greater range.
To use a repeater, you must know the repeater’s input and output
frequencies. Repeaters are usually identified by their output fre-
quency. For example, a repeater that has an output frequency of
146.94 is referred to as “the 146.94 repeater.” To determine the
input frequency, you must know the frequency
offset
(typically
600 kHz for the 2-meter band) and the
offset direction
(+ if you
add 600 kHz to the output, or – if you subtract 600 kHz from the
output).
Whether the offset is positive or negative depends on:
• which part of the band the repeater operates on
• local convention
• proximity of repeaters using the same two frequencies
To determine the offset and the direction, obtain a copy of
The
ARRL Repeater Handbook
(available at your local RadioShack
store or directly from the ARRL). That book lists the locations of
repeaters as well as their frequency and offset information.
A
above the displayed frequency indicates a positive offset,
while a above the frequency indicates a negative offset. If nei-
ther nor appears, the transceiver is set for simplex opera-
tion.
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