Motorola Gm300 Installation Manual

							Accessory Connections1-13
6.0 Accessory Connections
6.1 Accessory Connector Pin Functions
This section gives a description of the accessory connector pin functions.
CAUTION: The accessory connections shown are not compatible to some other models of
Motorola radios. Check the appropriate accessory or technical manual for further
information.
Ta b l e 1 - 4Connector Pin Functions
Pin Function Description
1External
Speaker -Speaker - and Speaker + (Pin 16) are used to connect an external speaker.
The audio PA is a bridge amplifier with a minimum load resistance of 3.2
Ω.
The internal speaker can be disabled by removing the control head.
Disconnect the internal speaker and assemble the control head back to the
radio.
2 External Mic
AudioExternal or Emergency Mic depends on dealer programming. This
microphone signal is independent of the microphone signal on the
microphone connector. The nominal input level is 80mV for 60% deviation.
The DC impedance is 660
Ωand the AC impedance is 560 Ω.
3Digital In 1This is a digital input only and the primary use for this pin is external PTT. This
pin must be used if fast DATA PTT is required.
(See Note 1).
4 Digital Out 2 This is a digital output only and the primary use for this pin is as an external
alarm output (See Note 3).
5Flat_TX_Audio
(NPD Data Out)This input is intended for injecting signals into the transmit path that should
not be filtered; for example, the analog output of a modem.
The nominal input level is 150mVrms for 60% deviation. The impedance is
greater than 25k
Ω.
6 Digital In 3 This is a digital input only. Function depends on dealer programming.
(See Note 4).
7GroundUsed as ground for both analog and digital signals
8 Digital In/Out 4 This is a digital input/output depending on dealer programming.
(See Notes 1, 2).
9Digital In 5 with
Wakeu p
Emergency
(NPD Call RQS)This is a digital input only. Emergency can be enabled via the CPS. To
activate, this line must be connected to ground; this will turn on the radio. The
CPS details which functions may be assigned to this pin by the codeplug.
10 Ignition Detect Connecting this line to the ignition line of the vehicle will automatically turn the
radio on when the ignition of the vehicle is turned on.
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							1-14INSTALLATION
11Receiver Audio
(NPD Data In)There are two possible outputs: (1) Discriminator Audio; and (2) Continuous
filtered RX audio. The nominal output level for Discriminator Audio is
330m Vrms at 60% deviation and for Filtered Audio 600m Vrms at 60%
deviation at 1kHz. Function depends on dealer programming. For NPD calls,
this uses discriminator audio and cannot be configured by the CPS.
12 Digital In/Out 7
(CTS)This digital input/output function depends on dealer programming.
13Switched
Battery VoltageThis voltage is available when the radio is switched on. The maximum current
is 1A.
14 Digital In/Out 8
Hook (Clear)This is a digital input/output depending on dealer programming.
(See Notes 1, 2).
This hook line is in parallel to the hook line of the control head microphone
connector. This port reads “0” when the microphone is on-hook and “1” when
off-hook. It is assumed that the hook is a mechanical switch, so the software
will always debounce this input.
15RSSIThis is an analog output which indicates the strength of the received signal.
16 External
Speaker +Positive output of radio’s audio PA (see Pin 1).
17Bus +This pin is used for flashing and for programming the radio.
18 Boot Control To enter Boot Mode this line must be connected to ground when the radio is
switched on.
19ReservedReserved.
20 Reserved Reserved.
Note 1:Digital Input
4.7 k
ΩInternal Pull Up Resistor to +5V.
Maximum Input Voltage accepted as Low = 0.6V
Minimum Input Voltage accepted as High = 3.0V
Note 2:Digital Output
4.7k
Ω Internal Pull Up Resistor to +5V
Maximum Current when Output Low = 10mA
Maximum Voltage when Output Low = 0.5V @ 10mA
Note 3:High Current Digital Output
4.7k
Ω Internal Pull Up Resistor to continuous B+
Maximum Current when Output Low = 200mA
Maximum Voltage when Output Low = 1.7V @200mA
Note 4:Digital Input
10k
Ω Internal Pull Up Resistor to +5V
Maximum Input Voltage accepted as Low = 0.6V
Minimum Input Voltage accepted as High = 3VTa b l e 1 - 4Connector Pin Functions
Pin Function Description 
						

							Accessory Connections1-15
6.2 Accessory Connection Plan
CAUTION: The accessory connections shown are not compatible to some other models of
Motorola radios. Check the appropriate accessory or technical manual for further
information. Ensure correct position of the accessory connector.
CAUTION: DO NOT short pin 16 or 1 on the accessory connector to ground; this may
damage the radio.
!
18 16 14 12 10
17 15 13 11 9 7 5 3
1198 6 4 2 20
86
8587
30
+12V
Ext. Alarm  4
86
8587
30
+12V
Ext. Alarm  4
+12V
+12V
SWB+  13
4A+12V
Ignition 10
1
16
GND 7MIC 2
PTT  3
GND 7
Emergency 9
12k
GND 7Alarm
RelayAlarm
Relay
GKN6272  External Alarm, Relay and Cable
RSN4001  Speaker 13W
HSN8145  Speaker 7,5W
RMN4027  Visor mounted Microphone
RLN4856  Footswitch w/Remote PTT
RLN4857  Pushbutton w/Remote PTT
RLN4858  Gooseneck PTT
RLN4836  Tri-State Emergency
      Footswitch and Cable
Ignition
Switch
Ignition Sense
on - off HKN9327  Ignition Switch CBL
* Note the location of pin 1.
! 
						

							1-16INSTALLATION 
						

							Chapter 2
REDUCING NOISE INTERFERENCE
1.0 Introduction
Electrical noise generated by the electrical system of a vehicle, as well as local ambient noise, can
interfere with normal operation of mobile radios. Satisfactory operation of a mobile radio may require
slight or heavy noise reduction, depending upon the relative strength of the radio signal, and upon
the ability of the radio to reject undesired noise. These requirements vary from one vehicle to
another, depending upon the vehicle type and required coverage area. When operating in a strong
signal area, a certain amount of noise interference can be tolerated. In weak signal areas, however,
noise reduction becomes very important. As a rule of thumb, noise levels create greatest
interference in the 25-50MHz band and reduce with increasing frequency.
Before attempting any noise reduction procedures, determine the noise source(s). Then, follow a
logical, systematic method of elimination until the interference is eliminated or reduced to an
acceptable level.
Care and patience must be exercised in locating and eliminating noise sources. There may be
several sources of noise, each slightly stronger or weaker than the other. Elimination of one source
may seem ineffective because another noise source remains active at a barely discernible
difference in level. Consult a service manual for the vehicle to determine what noise reduction
provisions the manufacturer applies when AM, AM/FM, or CB radios are installed as original
equipment. These radios are also subject to electrical noise interference, and the manufacturer may
install noise suppression components only upon those vehicles which require radio equipment at the
time of manufacture. These noise suppression components should be added in any first attempt to
suppress noise.
1.1 Noise Sources
The three major noise sources affecting mobile radio systems are: (1) radiated noise, (2) conducted
noise, and (3) induced noise. (See Figure 2-1 Noise Sources for typical vehicular noise sources.)
1.2 Radiated Noise
Radiated noise enters the radio through the antenna along with the desired signal and can block or
degrade desired communication. It can be generated by power lines, fluorescent lights, or by
electrical discharges from static build-up, ignition systems, or electrical motors. Radiated noise is the
most common cause of mobile radio interference.
CAUTION: Do not add interference elimination equipment to vehicles equipped with
electronic ignition systems before obtaining advice from the vehicle manufacturer. Addition
of some noise suppression components may interfere with proper operation of electronic
ignition systems and could seriously damage them.
! 
						

							2-2REDUCING NOISE INTERFERENCE
When a spark discharge or arc takes place through air, energy is radiated at frequencies from a few
kilohertz to hundreds of megahertz. This spurious radiation may have some energy radiated at a
frequency near or even identical to the desired radio signal. The standard receiver may be unable to
distinguish between the two signals (desired and noise). Therefore they both enter the receiver,
resulting in degradation of the desired signal.
It is impractical to prevent all arcing in the standard vehicle electrical system. In an 8-cylinder engine
running at 2,000 RPM, arcing occurs across the spark plugs at a rate of 8,000 sparks per minute or
133 sparks per second. Electrical motors and generators also produce arcs.
1.3 Conducted Noise
Conducted noise enters the radio through the points where the radio is attached to the vehicle’s
electrical system such as battery cables, ignition switch, chassis ground etc. It can be generated by
electrical transients, electrical motors, poor grounding points, or inadequate electrical system
filtering (from alternators, generators, voltage regulators, or weak batteries). Conducted noise can
degrade both transmit and receive performance of a mobile radio.Figure 2-1Noise Sources
Spark Plugs
Idle Stop
Solenoid
FL0830260-O
Spark Plug
Wires
Alternator or
GeneratorVoltage
RegulatorDistributor Ignition
Coil Wheel Static
Electric Fuel Pump Antenna Ground
or Location Radiated Noise Pick-upInadequate Terminal
or Fuse Block FilteringWindshield Wiper Motor
Heater Air Conditioner Blower
Electric Windows Motors
Hood Static
Power Seat Motor
FL0830260-O 
						

							Operation of a Conventional Ignition System2-3
1.4 Induced Noise
Induced noise enters the radio through the proximity of radio wiring to other wiring in the vehicle.
Electrical currents through the standard vehicular wiring can induce undesirable noise signals into
the radio cabling. Communication is degraded simply because the wiring provides a transformer-
type coupling action without any actual physical connection. Induced noise can degrade both
transmit and receive performance of a mobile radio.
2.0 Operation of a Conventional Ignition System
2.1 Introduction
To effectively reduce ignition interference in a vehicle, it is well to understand the operation of an
automobile ignition system.
Ignition is necessary in a gasoline engine to ignite the gasoline vapor and the air mixture in its
cylinders. The system is made up of the battery, distributor, breaker points, coil, condenser, and
spark plugs. The battery is the only electrical source of power in an automobile, so the lower battery
voltage must be stepped up to the high voltage necessary to arc across the spark plug electrodes.
This arc ignites the gas mixture.
2.2 Sources of Ignition Interference
In the conventional ignition system ( Figure 2-2 Typical Vehicular Ignition System, Simplified
Schematic Diagram) a mechanical circuit breaker (the cam and points in the distributor) opens the
primary circuit of the ignition coil, and high voltage is developed at the secondary. This high voltage
is synchronized and applied to each spark plug by the distributor. 
						

							2-4REDUCING NOISE INTERFERENCE
The battery is connected to the primary winding of the coil through the ignition switch. The primary
circuit is returned to the battery through the breaker points, which are bypassed by the condenser.
The points are normally closed. As the cam shaft is rotated by the engine, its lobes or corners open
and close the points in proper synchronization with the piston in each cylinder.
With the ignition switch on and the breaker points closed, coil primary current builds up at a rate
determined by the coil inductance.
When the breaker points open, primary current decreases and, by self-induction, an electromotive
force is induced in the primary which is many times greater than the battery voltage. The high
voltage inducted in the coil secondary causes a spark across the distributor rotor-to-spark plug wire
gap and then across the spark plug gap for a short interval of time when the breaker points open.
The condenser reduces arcing of the points.
The secondary circuit of the ignition coil, including the distributor rotor gap and the spark gap, is the
main source of ignition interference. The lead inductance and stray capacitance provide a tuned
circuit. Because the discharge of the circuit is through a low resistance (ionized spark gap), the
circuit tends to oscillate. The frequency and amplitude of oscillation vary as current changes in the
spark gap.Figure 2-2Typical Vehicular Ignition System, Simplified Schematic Diagram
HV Lead
Distributor
Spark  plug    leads
Spark
Plugs Ignition
Coil
Condenser Cam Breaker
Points Ignition
Switch
Battery
Ignition
Coil
CondenserStray
Capacitance
Cam Breaker
Points Ignition
Switch
BatteryRotor Gap
Lead Inductance
Spark Plug Gap
FL0830261-O 
						

							Detection of Noise Sources2-5
3.0 Detection of Noise Sources
3.1 Noise Detection Procedure
Detection of offending noise sources is the heart of noise suppression because, after the noise
source is identified, the solution becomes obvious. A logical methodical procedure is basic to the
effective noise suppression.
Use your available equipment to best advantage. A pick-up loop, about one inch in diameter, can be
connected to a portable CB radio or a mobile radio being operated at a frequency similar to the
installed radio frequency but from an isolated supply voltage. The pick-up loop can be moved
throughout the vehicle with the radio used as a radiated noise detector. Be sure the pick-up loop has
sufficient insulation to prevent the input of the radio from coming into direct contact with high voltage
points in the vehicle ignition system.
A non-polarized bypass capacitor, which has alligator clips firmly attached, can be used on a trial-
and-error basis to locate wiring which needs additional filtering. Keep capacitor lead lengths short
for best suppression. Ceramic disc capacitors are not as suitable or effective as automotive coaxial
capacitors. (See Figure 2-3 TLN8845_ Noise Reduction Kit for Alternator-Equipped Vehicles and
Figure 2-4 TLN6252_ Noise Reduction Kit for Generator-Equipped Vehicles for part numbers.)
Figure 2-3TLN8845_ Noise Reduction Kit for Alternator-Equipped Vehicles
Ignition
Switch
BatteryIgnition
Coil
Distributor
Breaker
PointsResistive Wire
(Note 2)
Resistor
Spark Plugs
(Note 2)
Notes:
1. Noise reduction can only be achieved if components are grounded properly.
2. Items not supplied in kit. See auto parts dealer.
1 2
3
FL0830262-O
Reference Quantity Motorola Description
Number Part Number
1 1 0100839913 Lead & Lug Assembly
2 1 0882571B02 Capacitor, Coaxial (0.1µF, 100V)
3 1 3000502396 Ignition Coil Suppressor Cable
- 1 0180782A52 Hood Wipers (2) and Mounting
Hardware Kit (not illustrated).
FL0830262-O 
						

							2-6REDUCING NOISE INTERFERENCE
Figure 2-4TLN6252_ Noise Reduction Kit for Generator-Equipped Vehicles
GeneratorIgnition
Switch
BatteryIgnition
Coil
Distributor
Breaker
PointsResistive Wire
(Note 2)
Resistor
Spark Plugs
(Note 2)
Armature
Field
Common GroundTo
Battery
To
Generator
FieldVoltage Regulator
ARMFLD
BAT
Notes:
1. Noise reduction can only be achieved if components are grounded properly.
Be sure that all the capacitors and the generator filed suppressor assembly are
grounded properly. This may require bonding straps for proper bypass
capacitor effectiveness.
2. Items not supplied in kit. See auto parts dealer.
FL0830263-O
1
2 3
4
56
1
4
1 4
FL0830263-O
Reference Quantity Motorola Description
Number Part Number
1 3 0100839913 Lead & Lug Assembly
2 1 0180700A88 Lead & Lug Assembly
3 1 0882571B02 Capacitor, Coaxial (0.1µF, 100V)
4 3 0882571B01 Capacitor, Coaxial (0.5µF, 100V)
5 1 0180700A89 Generator Field Suppressor Assembly
6 1 3000502396 Ignition Coil Suppressor Cable
- 1 0180700A91 Hood Wipers (2) and Mounting
Hardware Kit (not illustrated).