Maxon SP5050 CTCSS installation manual

LBI-39006

MAINTENANCE MANUAL

CHANNEL GUARD ENCODER/DECODER

OPTION MHCG1E (349A9730P27)

FOR

MONOGRAM SERIES PORTABLE RADIO

30-50 MHZ

TABLE OF CONTENTS

Page

SPECIFICATIONS ..............................................................................................................................................................1

DESCRIPTION......................................................................................................................................................................1

PINOUT/FUNCTIONS............................................................................................................................................2

INSTALLATION.....................................................................................................................................................2

ALIGNMENT ........................................................................................................................................................................3

NOISE SQUELCH THRESHOLD, 10 DB SINAD.................................................................................................3

TONE DEVIATION ADJUSTMENT.....................................................................................................................3

SCHEMATIC & OUTLINE DIAGRAM

Channel Guard Board...............................................................................................................................................4

PARTS LIST ........................................................................................................................................................................4

SPECIFICATIONS

Tone Frequencies 37 (Standard EIA)

67 to 250.3 Hz
Modulation Limits 500 - 1000 Hz
Decode Sensitivity 8 dB SINAD
Receive Response Time 250 ms max.
Encode Response Time 75 ms max.
Transmit Tone Distortion 5% max.
Transmit Intermodulation Distortion 15% max.
Power 5 Vdc, 4.5 mA
Temperature Range -30° to +60°C

ericssonz

LBI-39006

DESCRIPTION

Channel Guard Option MHCG1E is use with the 30-50
MHz Monogram Portable radio. It is a continuous tone coded
squelch system (CTCSS) capable of utilizing all 37 standard
EIA tone frequencies to provide a degree of privacy in voice
communications and allow you to hear only those calls
intended for you. Additionally, a non-standard tone, 97.4 Hz
and a disabled state called "No Tone" are available. All are
programmed by channel and mode, transmit or receive. This
allows radios with Channel Guard to be programmed so that
each channel may have different encode/decode tones or may
have no encode or decode at all. T he subaudible tone assigned
to your transmit frequency precedes the voice message. Its
purpose is to activate the decoder and open the receiver to
allow the message to be heard. Table 1 identifies the standard
EIA CTCSS tones.

Operational control of the programmed Channel Guard
frequencies is controlled by an eight bit digital code sent
serially by the radio's microcomputer from the EEPROM to
the Channel Guard when the radio is first turned on, when the
channel is changed, and when the radio changes from receive
to transmit and transmit to receive modes.

The Channel Guard board contains a single IC (integrated
circuit) and associated discreet components mounted on a
printed circuit board. The PCB is located underneath the Top

Panel PCB and is plugged into the optio n interface connector
located on the main PCB. See Installation.

Table 1 Channel Guard Tone Frequencies

No. Freq. Hz No. Freq. Hz.

01 67.0 20 131.8
02 71.9 21 136.5
03 74.4 22 141.3
04 77.0 23 146.2
05 79.7 24 151.4
06 82.5 25 156.7
07 85.4 26 162.2
08 88.5 27 167.9
09 91.5 28 173.8
10 94.8 29 179.9
11 97.4 30 186.2
12 100.0 31 192.8
13 103.5 32 203.5
14 107.2 33 210.7
15 110.9 34 218.1
16 114.8 35 225.7
17 118.8 36 233.6
18 123.0 37 241.8
19 127.3 38 250.3

PINOUT/FUNCTIONS

PIN FUNCTION

1 PTT OUT - Connects to pin 2; allows PTT signal to pass through
2 PTT IN - Connects to pin 1; allows PTT signal to pass through
3 GND - ground
4 TX AF IN - Transmit audio input; allows CTCSS tones to be added
5 1 MHz - Frequency reference for U1.
6 + 5 Vdc - input power, 4.5 mA
7 DECODE - CTCSS decode state output to the radio; +5 Vdc indicates tone is present, 0 Vdc indicates it is not.
8 Not used
9 DATA - Data received from EEPROM to set tone frequency and mode (encode/decode)
10 SQ POT (dual purpose) - Grounded - disables the CTCSS decode function. Ungrounded - allows R6 to control the

radio's squelch threshold and enables the tone decode function

11 RX AF IN - Radio detector input from radio. Allows audio frequencies below 300 Hz to be filtered out and permits

CTCSS tone detection..

12 CLOCK - Used to shift data out of EEPROM. R8 &C4 delays data out so that the rising edge seen by U1 comes after

the data appears on pin 9.
13 STROBE/ENABLE - Input used to strobe data into its internal control register.
14 RF AF OUT - Receive audio, after U1 filters out the Channel Guard tones, to radio volume control.
15 TX AF OUT - Transmit audio, after Channel Guard tone has been added, to radio modulator.
16 PUSH TO MON - Not used by Channel Guard. Radio microprocessor monitors this signal and always unmutes the

receiver.

Copyright October 1993, Ericsson GE Mobile Communications Inc.

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