User's Manual

Table Of Contents
MM102558V1 R1A
The main programmable station data parameters include Transmit and Receive frequency, Channel
Guard, TX Pot settings, CG Pot settings, RF Simplex/Rpt and PA Power settings. The following sections
include a brief description of each parameter.
5.6.2.1 Transmit and Receive Frequency
The System Module is programmed with most of the station’s features including transmit and receive
frequency assignment. Once the correct control station type has been defined, up to twelve (12) channels
may be programmed into one station (16 channels in models with previous vintage System Modules).
5.6.2.2 Channel Guard
A Channel Guard (CG) is a sub-audible (below 300 Hz) tone, used to control one or more functions of a
base or repeater station. CG tones may be used to open (or un-mute) the station’s receiver audio circuit,
provide PTT signaling to stations in repeater mode, or provide control of other station functions. There
are two types of Channel Guard (CG) available:
Tone Channel Guard (CG)
Digital Channel Guard (DCG)
The System Module, located in the MASTR III ADC T/R Shelf, can encode CG or DCG tones (generate
tones to be used by the transmitter) or decode received CG or DCG tones. The System Module may be
programmed with different CG or DCG tones on each channel. Each individual channel may also have a
different transmit and receive CG or DCG tone; including a mix, such as DCG for transmit and a CG for
receive.
For DC or Tone Remote controlled stations, the CG Disable (monitor) function, controlled by DC or
Tone Remote control signaling, may override the receiver CG or DCG decoding by un-muting the
receiver and allowing all on-frequency activity to be monitored. When CG or DCG tones are used to key
repeater stations, the transmitter is activated only when the proper CG or DCG tone is decoded, regardless
of the CG Disable condition.
On the System Module, setting the CG MONITOR switch in the UP position (LED indicator lit), causes
the receiver to un-mute and operate in the carrier squelch mode. This has no affect on repeater stations
using DC or DCG tones to signal a PTT request to the transmitter. The transmitter is activated only if the
proper CG or DCG tone is present on the received signal.
5.6.2.2.1 Tone Channel Guard
The industry standard Continuous Tone Coded Squelch System (CTCSS) or CG tones range from 67 Hz
to 210.7 Hz. Extended CG tones above 210.7 Hz are available, but can cause some degradation in
specifications.
The System Module monitors the station’s receive demodulated audio output for a CG tone and signals
the station when the proper CG tone is received. Once the proper receive CG tone has been detected, the
System Module un-mutes the receive audio and causes other pre-programmed actions to occur.
In addition, the System Module generates any TX CG tones programmed on a channel and routes the
audio to the TX Synthesizer card to modulate the carrier. A 135-degree phase shift in the CG tone is also
generated at the end of a transmission for 160 milliseconds after the transmitter is un-keyed (PTT button
released) to initiate STE in the receiving station, if equipped with STE.
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