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5.0 About Radio Operations.
5.1 Terminology.
In a wireless Land Mobile Radio (LMR) Communications system, there are
two modes of operation: DIRECT (communicating on the same transmit and
receive frequency between radio users, sometimes called Radio to Radio,
Car to Car, or SIMPLEX); and over a REPEATER (where a portable or mo-
bile radio transmits on one frequency and receives on another).
In DIRECT/SIMPLEX MODE, there may be obstacles such as buildings or
uneven terrain affecting the transmission over long distances of communica-
tions between two or more low power (ex. 5 watt) portable radios. In a RE-
PEATER configuration, a radio receiver and high power radio transmitter
(example 50 to 150 watts) with two antennas is located on a mountain top or
elevated location.
When using a handheld radio the Repeater due to its better elevated loca-
tion and higher output power, it receives much better the low power signal of
the hand held or other radio units. Once received, the transmitter retransmits
simultaneously the received radio transmission from the handheld or mobile
radio on a frequency that differs from the received signal at higher power.
When strategically located on top of a high building or a mountain top, the
Repeater can greatly enhance the performance of a wireless network by al-
lowing communications over distances much greater than would be possible
without it. In this case coupled with higher power, the Repeater
“
repeats
”
the
communications from the hand held or mobile unit that it receives, and in-
creases the range due to the higher power and better antenna and location
of this relay station.
TIP: Using “Talkaround” feature:
When Teams do not have a simplex
private channel to work with and only have a repeater channel available,
some radios such as this K911 may allow you to preprogram a hot key to set
the repeater channel into
TALKAROUND
mode. In this setting the repeater
stays the same but radios set to TALKAROUND will transmit and receive on
the repeater
’
s output.
(“
A
”).
This only works if both users are within range of
each other as no repeater is used. In this fashion field units will also hear
the repeater
’
s transmissions and may respond if needed by turning TALKA-
ROUND off.
Repeater
Receive: 156.090 MHz,
“
B
”
Transmit: 154.875 MHz,
“
A
”
When it Receives a signal the repeater transmits what it receives
Portable Unit 1
Receive: 154.875 MHz.
“
A
”
Transmit: 156.090 MHz,
“
B
”
Portable Unit 2
Receive: 154.875 MHz,
“
A
”
Transmit: 156.090 MHz,
“
B
”
Repeater Operation
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8.2 IN DIGITAL CHANNEL MODE:
tree as follows:
