Ericsson LBI-31629B User Manual

LBI-31629B

Maintenance Manual

M-PD



SYSTEM

136-174 MHz PERSONAL TW O-WAY FM RADIO COMBINATION

ericssonz

INCLUDES

SERVICE SECTION . . . . . . . . . . . . . . LBI-31677

Ericsson Inc.

Private Radio Systems Mountain V ie w Roa d Lynchbur g, V ir ginia 24502 1-800-528-7711 (Outside USA, 804-528-7711) Printed in U.S.A.

TABLE OF CONTENTS

Page

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

OPTIONS AND ACCESSORIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

COMBINATION NOMENCLATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

DESCRIPTIO N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

SYSTEM ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

INTRINSICA LLY SAFE USAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

BATTERIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

ACCESSORIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

MEMORY EFFECT IN NICKEL-CADMIUM BATTERIES: . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

REDUCED CAPACITY IN NICKEL- CADMIUM BATTERIES: . . . . . . . . . . . . . . . . . . . . . . . . 13

INTERCONNECTION DIA G RAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

OUTLINE DIAGRAMS:

Radio Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Controller Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Signaling Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

LCD Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Battery Packs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

SCHEMATIC DIAGRAMS:

Radio Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Controller Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Signaling Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

LCD Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Battery Packs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

MECHANICAL PARTS BREAKDOWN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

PARTS LISTS:

M-PD Radio Chassis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Mechanical Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Radio Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Controller Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Signaling Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

LCD Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

LBI-31629

SPECIFICATIONS

SYSTEM

Frequency Range FCC Identification Number 136 MHz to 160 MHz AXA9WNTR-145-A 150 MHz to 174 MHz AXA9WNTR-145-B

Frequency Stability 5 PPM Battery Drain (at 7.5 VDC)

Standby 65 Milliamperes Receiver (Rated Audio) 195 Milliamperes Transmitter 1.9 amperes

Dimensions (H x W x D) (With Standard Capacity) 183 x 69 x 43 mm (With High Capacity (short) Battery) 183 x 69 x 43 mm (With High Capacity (long) Battery) 219 x 69 x 43 mm (With Extra High Capacity Battery) 219 x 69 x 43 mm

Weight (With Standard Capacity Battery) 24 ounces (With High Capacity (short) Battery) 24 ounces (With High Capacity (long) Battery) 29 ounces (With Extra High Capacity Battery) 29 ounces

Operable Temperature Range -30°C to +60°C

TRANSMIT

RF Power Output 0.5 to 5 Watts Spurious Emiss ions -3 7 dB m Maximum Deviation 5 kHz FM Hum & Noise (EIA) -45 dB Audio Distortion (60% MOD) 3% Frequency Stability 5 PPM

(-30°C to + 60°C) RF Load Impedance 50 ohms Microphone Sensitivity Less than 90 dB SPL

(EIA 60% MOD) Maximum Attack Time 25 milliseconds

(PTT Pushed) Audio Frequency Response Within +1 and -3 dB of a 6 dB/octave

pre-emphasis from 300 Hz to 3000 Hz.

RECEIVE

Sensitivity (12 dB SINAD) -116 dBm Spurious Emiss ions -5 7 dB m Spurious Response Rejection 72 dB (Minimum) IM Distortion Rejection 70 dB (Minimum) Adjacent Channe l Se l e ctivity 70 dB (3 0 kHz) Squelch Sensitivity 6 dB SINAD (Minimum) Adjustable Distortion (EIA 0.5 Watt) 5% (Maximum) Audio Frequency Response Within +1 and -3 dB of a 6 dB/octave

de-emphasis fr o m 30 0 Hz t o 30 00 Hz.

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LBI-31629

UHF

800 MHz

TANDARD MODEL SCAN MODEL SYSTEM MODEL

OR OR

GENERAL ELECTRIC

BELT CLIP

PDHC15

HEADSET/MIC

SWIVEL MOUNT

PDAB10

PDHC16

CARRYING CASES

WITH BELT LOOP PDHC11 PDHC12

ITH SWIVEL MT PDHC13 PDHC14

EARPIECE

PDAC10

SHOULDER STRAP

PDHC18

SPKR-MIC

PDAE-10

GENERAL ELECTRIC

COMBINATION NOMENCLATURE

Digits 1 & 2 Digit 3 Digit 4 Digit 5 Digit 6 Digit 7

Product

Code

PD G

Frequency

Range

136-160

MHz

150-174

MHz

Controller Selectivity Stability

System

Standard

5 PPM

Power Souce

HIGH CAP.

NICD

STD CAP.

NICD

X HIGH CAP.

NICD

Battery

HIGH CAPACITY

BATTERY

(Standard)

STANDARD CAP ACITY

PDPA10

(Optional)

TOP VIEW

FRONT VIEW

MULTI-CHARGER

H2A2L2A 121 VAC 16 HR H2A2J1A 121 VAC 1 HR H2A2M2A 240 VAC 16 HR H2A2N1A 240 VAC 1 HR

INTERFACE CONNECTOR

(Provided with PDAB10)

TOP VIEW

FRONT VIEW

DESK CHARGER

H2A1L2A 121 VAC 16 HR H2A1J1A 121 VAC 1 HR H2A1M2A 240 VAC 16 HR H2A1N1A 240 VAC 1 HR

GE-STAR LANYARD

PDAC12

GENERAL ELECTRIC

VEHICULAR CHGR/RPTR

H2V01 - Vehicular Charger H2V02 - Vehicular Chgr/Rptr Control

DESCRIPTION

Ericsson GE’s M-PD System Personal Radio is a highquality, high-performance, two-way, FM, communications unit consisting of a transmit/receive circuit with a frequency synthesizer controlled by a microprocessor. The M-PD Personal Radio is ideal for use in public services by providing the following features:

48 Channel Capability

•

mixture of numerics (0 - 48) and alphanumerics through the eight characters in the LCD display. Channel control can come from either the up/down channel ramping buttons, front keypad entry or the "Home" Channel feature.

Eight Programmable Modes

•

programmable with any number of channels in each mode: the sum of channels and blank channels in all modes equal to 48.

Programmable Multi-Tone Channel Guard (CTCSS)

•

Encode/Decode

: Channel Guard tone frequencies within the range of 67 Hz to 210.7 Hz, including all of the standard EIA frequencies, may be programmed. Different encode/decode, encode only and with/without Channel Guard frequencies are also programmable into the radio.

: Channel designation can be a

: Up to eight modes are

The same channel is used with and without Channel Guard by programming two different radio channels with the same frequency information but only one with Channel Guard capability.

Programmable Multi-Code Digital Channel Guard

•

Encode/Decode

: Similar capability as with Tone Chan-

nel Guard is provided.

Programmable Carrier Control Timer

•

: Personality information includes an optional period of transmit time from 15 to 120 seconds, after which the unit will automatically unkey and provide an alerting tone. This feature is reinitiated on every PTT and the alert tone is removed upon release of the PTT.

Minimum Volume Level

•

: Personality information includes a minimum volume level below which the radio controls cease to reduce the volume.

Squelch Tail Elimination

•

: Squelch and audio circuits are designed so that annoying squelch pops which may occur at the end of received messages are minimized, both with and without Channel Guard. This system is compatible with an existing GE system.

Programmable Squelch

•

: The noise squelch opening

threshold can be programmed for each channel.

LBI-31629

• Channel Busy Lock Out: Personality information in-

cludes the capability to prevent the transmitter from operating on a channel where carrier activity is present. The "Channel Busy" indicator (BSY) is active during this time.

• Automatic/Manual Power Levels: The desired power

level on each channel can be programmed into the radio personality such that it is automatically selected channelby-channel or selected manually.

• Home Channel Feature: A "Home" channel can be pro-

grammed into the radio which is selected by pressing the "Home" button. This allows a user to quickly reach a reference channel.

• Surveillance Feature: In addition to the ability to pro-

gram the display 1ighting on or off per chan nel, the sidetone beep related to the operation of a radio control is capable of being dis abled on a channel by channel basis.

• Eight Character Alphanumeric Liquid Crystal Dis-

play: This display is used to exhibit the condition of the

radio. It shows: Channel Designation, Signaling ON/OFF, Transmit, Volume Level, Battery Condition, Channel Busy, High/Low Power output, SCAN 0N/0FF and Priority 1 & 2.

• Simple Remote Control Capability: By connection

through the UDC (Universal Devices Connector) a simple speaker/ microphone can be operated which can also control PTT and Volume le ve l.

• Push Button Controls Only: All control functions on

the radio, with the exception of the power ON/OFF switch, are operated through push button controls on the top and sides of the radio.

• Programmable through UDC: The entire personality

of the radio is programmed into the radio through the UDC through four connections. The Ericsson GE TQ2310 Universal programmer is one method of programming the radio, while the capability exists to interface to an RS-232 device at a maximum of 1200 baud.

• Keyboard Enable: Pressing two keypad keys (Secon-

dary Function and KEY BD) in sequence activates the front DTMF keyboard. The user can then change radio functions as required. The top keypad is not protected in this manner for ease of using the frequently switched functions (volume, channel, Signaling On/Off, . . .etc.).

• Two-Tone Sequential Encode/Decode: Selective call-

ing encode, decode or encode/decode is enabled or disabled on each individual channel. Three simultaneous unique decodes are available for each channel to allow large systems the capability for individual and group calls.

Compatibility with Channel Guard, Digital Channel Guard, GE-STAR, DTMF, Dual Priority and Scan are maintained. Various audible alerting signals are available on choice when programming the radio.

• DTMF Encode Reperatory Dialing: When enabled by

the information programmed into the personality of the radio, the DTM F encode function ca n be used by eith er manually dialing from the keypad or by recalling a complete number stored in memory. Ten stored numbers, including the 1ast number dialed, up to 16 digits are easily recalled to the display for viewing. A conv enien t displa y overflow and shift mechanism is incorporated into the display contr ol procedure.

It is not necessary to press the PTT switch while dialing. Features needed for overdialing, autopatch and paging terminals, including programmed delays, pauses and the generation of the "*" and "#" DTMF pairs are included.

• Programmable Dual-Priority Scan: The radio is pro-

grammed to listen to a selected channel while scanning back to two priority channels. The radio reverts to the priority 1evel channels should any activity occur on those channels. There are two 1evels of priority. The first priority channel takes precedence over the second priority channel and the second priority channel takes precedence over the user selected channel.

• Manual High/Low Power Selection: If programmed

into the radio, t he user will be able to manually select either high or low RF power output through the front panel keyboard.

Physically an M-PD radio consists of three printed wire

board assemblies an d a battery pack as follows:

a. A printed wire board specially shielded with zinc

alloy on which t he radio assembly (transmit/receive/synthesizer) is assembled.

b. A Logic control board containing the microproc-

essor.

c. A Display board ca rrying various display and in -

dicating circuits.

d. A battery pack that fits the M-PD main unit.

e. Light weight metal front and back housing.

Radio Assembly

Transmit:

The transmit circuit is made up of four major circuits as

follows:

a. Wideband Hybrid Exciter: Amplifi es the sig nal

from the frequency synthesizer with about 21 dB gain.

b. Wideband Power Amplifier: Amplifies the out-

put signal of the exciter (13 d B t o 18 dB) to the desired output level for transmission.

c. Wideband Power Control Hybrid IC: Can re-

duce the transmitter output level by 10 dB.

d. Output Low pass Filter (LPF): Consists of a

three stage LPF to eliminate higher harmonics.

The transmitter completely covers the band within the split with n o adjustments except for the RF power control voltage from the controller.

Receive Circuit:

The receiver consists of three ma jor circuits as follows:

a. Front End Circuit: Consists of single stage pre-

amplifier with about 12 dB gain and the pre BPFs and the post-BPFs of the pre-amplifier.

b. First Mixer and IF Circuit: A special double

balanced mixer provide a 45 MHz first IF, which is coupled through band pass filter (BPF) and an IF amplifier to get the desired first IF signal.

c. Second IF (455 kHz): Consists of one IC and

one BPF, containing the second mixer, second IF amplifier and FM detector. The second IF output provides the Logic section with audio output.

Frequency Synthesizer:

The frequency synthesizer is made up of three major modules as follows:

a. VCO Module: The VHF band frequency syn-

thesizer has two VCO’s, one for transmitting and one for receiving. The transmitter is modulated at both the VCO and the VCTCXO.

b. VCTCXO Module: The VCTCXO is a tem-

perature compensated crystal oscillator to provide a 13.2 MHz reference frequency and has modulation capability.

c. Phase Lock Loop: Consists of a frequency di-

vider and a low current drain C-MOS IC for phase comparison.

Logic Circuit

The Logic circuit consists of a LCD board, a signaling

board and a control board with an audio IC as follows:

a. LCD Board: Includes LCD driver circuits for

the display.

b. Signaling Board: Includes a CMOS microcom-

puter, an audio amplifier and a comparator circuit. This board provides DTMF and GE STAR encoding, sequential Two Tone decoding and control for the SCAN operation.

c. Control Board: Carries a microprocessor, a bat-

tery backed RAM, audio circuit and I/O interconnections with the frequency synthesizer and the display. Thus, this board commands all the functions and operation of the M-PD ra dio.

d. Audio IC: Includes transmitter and receiver

audio circuits.

Power Supply

The M-PD battery pack connects to the bottom of the MPD radio to supply 7.5 Volts DC to the unit. The battery packs are available in three capacities: standard, high and extra high. To charge these battery packs, charges are available in three different styles: a desk charger, a wall mount multicharger and a vehicular charger.

OPERATION

The M-PD Personal Radio is delive red disassemble d into three parts:

1. M-PD Radio (Main Unit)

2. Antenna

3. Battery Pack

LBI-31629

Assemble these parts into one unit according to the following procedure and as shown in Figure 1 - M-PD Operating Controls and Accessories.

NOTE

Either the antenna or the RF connector should be connected to the M-PD radio main unit, as desired. If the RF connector is inserted in the receptacle, located in the side of the unit, the antenna connector circuit will become open.

1. Screw the antenna or the RF test connector In its receptacle. A clockwise turn will insert the antenna or RF test connector, while a counter clockwise turn will remove them.

2. Slide the battery pack along the bottom of the MPD main unit from the arrow-marked direction, shown in Figure 1, until the b attery pack locks into place.

Operating Procedure (Refer to Figure 1)

Display

If BSY If BSY lights, it means that the channel is busy.

4. Adjust the audio volume to the desired level by pressing the ▲ mark side (to turn the volume up) or the ▼ mark side (to turn the volume down) of the VOL switch . As the VOL switch is operated, the indication in the display window changes 1 through 31 (about 45 dB). The volume le vel cannot be set lower than the lev el programmed in the minimum volume option.

To Send a Message:

Hold the radio so that the antenna is vertical. T he n, pre ss the Push-to-Talk (PTT) bar on the left side of the main unit an speak directly into the microphone in a clear and distinctive voice. Always release the PTT bar as soon as you stop talking.

Upon pressing the PTT bar, an indication will appear in the display window .

To Receive a Message:

1. Slide the Power switch on the side of the battery pack up to turn on the radio.

2. Select a desired channel within a selected mode by pressing the ▲ mark side or ▼ mark side, of th e CHAN switch 6 while watching the indicaion in the display window.

An operating channel may also be selected by pressing the CHAN key on the front keypad. Pressing this CHAN key displays the current operating channel. To select a different channel, key in the channel number, then press the CHAN key. The display will indicate the new channel name or number and update the display flags.

An operating mode may be selected by pressing the MODE key, also located on the front keypad. Pressing the MODE key displays the current mode. To select a different mode, key in the desired mode number, then press the MODE key. The new mode will be displayed.

3. To monitor the channel for idle or busy, watch for the "BSY" symbol to be illuminated in the display or audibly monitor the channel by simultaneously depressing bot h the ▲ and ▼ volume buttons.

Lights while you are speaking.

Lights for high power.

NOTE

The M-PD unit is provided with an optional timer which inhibits continuous transmission beyond about 12O seconds. When transmission is interrupted due to "time-out", you can resume transmission by releasing and then pressing the PTT bar again.

To Make a Telephone Call:

You can make a telephone call by direct entry through

the DTMF keypad or through the ber feature.

1. Turn the radio on, adjust the audio level and select

the desired operating channel as covered in TO

RECEIVE A MESSAGE.

Recall Telephone Num-

Figure 1 - M-PD Operating Controls and Accessories

LBI-31629

2. Use the DTMF keypad or use the Recall Telephone Number key (RCL) to enter the digits of the telephone number.

3. Press the secondary key and then press the SEND key. An optional tone (sidetone) may be heard as each digit is transmitted.

4. When someone answers, press the PTT bar and speak directly in to the grille on the radio, or across the face of an external microphone. Release the PTT bar as soon as you stop talking. Messa ges can not be received when the PTT bar is pressed.

5. When the conversation is completed, press the (#) key to disconnect from the telephone system.

To Recall a Telephone Number:

The RCL butt on is used to recall the last number dialed

or to recall one of the ten 16-digit numbers that can be stored in memory.

To Recall the Last Number Dialed:

1. Press the secondary key and then the RCL button.

2. Then press the secondary key and then the SEND key as in Step 3 of To Make a Telephone Call.

To Recall a Telephone Number Stored in Memory:

1. Press the key number of the memory location (1 through 9).

2. Press the secondary key and then the RCL key.

• Signaling Board: provides additional software con-

trolled signaling functions

Interconnection of the control board with other boards and control circu its is made with flexible circuit boards and connectors. All control leads which are "barred", such as PTT, mean that the function indicated occurs when the lead is in a low voltage condition.

Circuit illustrations shown in the following text are simplified representatives of actual circuits. They are intended only to illustrate basic circuit functions.

RADIO BOARD

Transmit Circuits

The M-PD transmit circui t, as shown in Figure 2 - Block Diagram, consists of the following integrated circuit modules:

• Amplifier (TX-Amp)

• Power Amplifier (P A)

• Power Controller (PC)

• Antenna Switch (AS)

• Filter Network (FN)

Amplifier Module (A201):

Amplifier module (TX-Amp) A201 is a single stage RF amplifier hybrid IC. A 0 dBm RF signal on the input will produce a +23 dBm signal on the output (refer to Figure 3). This module is broadband and does not require tuning.

Figure 2 - Block Diagram

3. Press the secondary key and the SEND key as in Step 3 of To Make a Telephone Call.

SYSTEM ANALYSIS

Ericsson GE M- PD P ersonal radios a re two-way, FM radios designed for public communications. The M-PD System radio consists of four printed wire boards as follows:

• Radio Board: carries the transmit, receive and fre-

quency synthesizer circuits

• Control Board: supports logic, control and audio

processor circuits

• Display Board: carries LCD displays

Figure 3 - Amplifier Module (TX-Amp)

Power Amplifier Module (A202):

Power Amplifier (PA) A202 is a three stage, wide band amplifier module with an input and an output impedance of 50 ohms (refer to Figure 4). The first stage of the PA module has the DC power supplied by power control transistor

LBI-31629

Q202. The RF power output from Pin 2 of the TX-Amp module A201 is connected through a resistor attenuator to Pin 1 of the PA module where it is applied to the input of the RF power amplifier stages. The RF power amplifier stages amplify the input from the TX-Amp module to a typical power output level of 6 watts at Pin 5. The output at Pin 5 is connected through the power control hybrid IC A203 (PC) and TX-RX switching diode CR201 to low pass filter network FN. A min imum power level of 5 watts is on the output of the filter network.

Power Control Module (A203):

The RF power output of the radio is regulated by sensing variations in the RF power output of the transmit PA module to control the supply voltage to the first stage of the PA module (refer to Figure 5). Supply voltage cannot be applied to the first stage of the PA module until the transmit circuit is keyed, applying 5.4 Volts to Pin 11 of Power Control (PC) hybrid IC A203. When the transmit circuit is key e d , the output of a reference amplifier, determined by the High-Low power control, is applied to the positive (+) input of a comparator circuit.

The output of the final PA is connected to Pin 1 of the PC module and to the 50 ohm coupled line. The detected voltage of the CM coupled ou tput is applied to the negative (-) input of the comparator circuit. The amplifier is enabled when the transmi t circuit is keyed, u ntil then, the output of the amplifier is low and transistor Q202 is held off. As the PA module begins to increase output power, the detected voltage causes the series regulator circuit to regulate the supply voltage to maintain constant RF output power.

Filter Network (FN):

The output of the PA module is connected to filter network FN through TX-RX switching diode CR201. The FN network is a passive LC low pass filter with an insertion loss of less than 0.5 dB in the pass band. It also has a rejection greater than 45 dB in the stop band. The output of the FN is connected to the system antenna or to the UDC connector.

RF Amplifier/Mixer:

The RF Amplifier/Mixer circuit contains two third order band pass filters (FL301 and FL302), an RF amplifier circuit (Q301) and a double balanced diode mixer circuit (A301). Refer to Figur e 6 - RF Amplifier/Mixer. RF from the antenna or UDC connector is coupled through transmit low pass filter FN and RF switching diode CR201 to the input of the RF amplifier circuit. Low pass filter FN is used in the receive circuit to provide additional receive selectivity. The RF signal on the input of the RF amplifier is first coupled through band pass filter FL301 to the input of grounded emitter, broad band RF amplifier transistor Q301. This amplifier provides 12 dB of power gain to reduce thermal noise. The output of the RF amplifier is coupled through band pass filter FL302 to drive double balanced m ixe r A301.

The RF signal from the RF amplifier and the injection frequency from the synthesizer circuit, provide a difference of 45 MHz IF on the output of the mixer. The double balanced Mixer has a typical conversion loss of 6 dB between the RF input and IF output. All inputs and the output of the RF Amplifier/Mixer one 50 ohms impedance. The +7 dBm injection frequency level, provided by the synthesizer and amplifier circuit transistor Q106, is connected to the injection frequency input through a 50 ohms matching circuit. The output of the Mixer circuit is connected to the input of the first IF Amplifier.

First IF Amplifier:

The first IF amplifier contains two amplifier circuits and two crystal filters of two and four poles respectively (refer to Figure 7). The first IF signal (45 MHz) from the first mixer circuit connects to the input of pre-amplifier transistor Q302 through pre-crystal filter FL303 with an impedance of approximately 3K ohms. Pre-amplifier Q302 provides a 17 dB power gain. The output is connected to the input of IF amplifier transistor Q303 through crystal filter FL304. IF amplifier Q303 has a 13 dB power gain, an input impedance of approximately 3K ohms and an output impedance of approximately 2.2K ohms.

Figure 4 - Power Amplifier

Receive Circuit

The M-PD receive circuit, as shown in Figure 2, consists

of the following circuits:

• RF Amplifier/Mixer

• First IF Amplifier

• Second IF Amplifier/Discriminator

Second IF Amplifier/Discriminator (A302):

The Second IF Amplifier/Discriminator circuit contains FM IF IC A302 (HA12442V) and 455 kHz ceramic filter FL305 (refer to Figure 8). The FM IF IC con tai n s a local oscillator, mixer, IF amplifier, FM detector and an audio amplifier. The 45 MHz IF output from the first IF amplifier is connected to the input of second IF amplifier A302a, Pin 2 of HA12442V and converted to the second IF frequency (455 kHz). The second IF output is connected to Pin 7 of HA12442V through the 455 kHz ceramic filter to the IF amplifier and FM detector circuits. The recovered audio from the FM IF IC is connected to J102-4.

Figure 5 - Power Control Module

LBI-31629

Figure 6 - RF Amplifier/M ixer

Synthesizer Circuit

The Synthesizer circuit co ntains Phase-Lock-loop module (PLL) A102, VCTCXO Reference Oscillator module A103, TX/RX Voltage Controlled Oscillator module (VCO) A106 and a Low Pass Filter amplifier (LPF). Refer to Figure 9 - Synthesizer. The VCO used to generate the receive and transmit reference frequencies is phase locked to a stable VCTCXO reference oscillator through the use of the PLL. This feedback loop divides the VCO frequency down to a signal in the range of 7 MHz - 10 MHz; divides this signal with a programmable divider to 5/6.25 kHz and generates a VCO control signal by comparing the 5/6.25 kHz feedback with a 5/6.25 kHz signal derived by dividing a 13.5 MHz VCTCXO by 1056. As the least significant bit in the programming is changed, the VCO is forced to change by 5/6.25 kHz.

The synthesizer circuitry is contained on two modules, the VCO module A106 and the VCTCXO reference Oscillator module A103.

Phase-Lock-Loop Module (A102):

The PLL module A102 contains a reference frequency, divider, phase detector and a programmable divider. The phase detector DC voltage output signal is filtered with a passive low pass filter followed by a 6.25 kHz filter to reduce the level of reference modulation on the VCO. This DC out put re presents th e error bet ween the VC O frequency

(phase) and the reference (VCTCXO) and is applied to the VCO on fr equency. A lock detect output is developed from Pin 9 output of A102. This output is checked by the microcomputer to prevent transmission before the VCO is on frequency.

Serial data from the microcomputer is shifted into the PLL to set the division parameter which establishes the frequency. A clock signal is provided on another input and the data is latched with the enable input.

Voltage Controlled Oscillator A106:

The VCO uses a low noise, high gain transistor as the basic oscillator. The resonant circuit, which determines the frequency of oscillation, is formed by a High Q coil which i s used to set the center frequency at the factory. The output of each VCO (TX and RX) is coupled into a cascade amplifier which produces +3 dBm. The output of the RX-VCO amplifier is coupled into the receive first double balanced mixer circuit A301 through buffered amplifier Q106. The TXVCO amplifier output is directly connected to the TX-Amp input through attenuator circuit R201, R202 and R203.

VCTCXO Reference Oscillator A103:

The A103 oscillator module is self contained, fully temperature compensated and operates at a frequency of 13.2 MHz. The oscillator als o has modulation capability. Frequency is adjusted by a trimmer while monitoring the transmit circuit output at the antenna jack.

Figure 7 - First IF Amplifier

Figure 8 - Second IF Amplifier/Discrim inator

Figure 9 - Synthesizer

LBI-31629

CONTROLLER CIRCUIT

This controller circuit consists of control circuits and audio circuits. P hysically, this circuit consists of three circuit boards as follows:

• Control Board

• Signaling Board

• LCD Board

Control Board

The Control board cons ists of the following circuits (see Figure 2):

• CMOS Microcomputer (A1)

• RAM with Lithium Battery (A2 plus BT1)

• Audio Processor (A3)

• Audio Amplifier (A4, A6)

• Voltage Regulator Circuits (A7, A9, Q2, Q3, Q10 and

Q11)

• External Data Buffer (A5)

Microcomputer (A1):

The microcomputer provides various software for controlling the radio unit as follows:

• Loading data to the frequency synthesizer

• Fetching and processing the PTT, monitor, channel se-

lection and volume control

• Loading data to the LCD display

• Controlling the audio circuit (Processor)

• Encoding/decoding the Channel Guard and digital

Channel Guard

• Controlling the loading interface for the radio data

(channel number and signaling)

RAM (A2):

RAM has a capacity of 2K bits X 8 for storing various data for controlling the radio. The data is entered from the outside to the microcomputer through the UDC connector and then to the RAM. The data mainly consist of the following:

• Channel Frequency Data

• CG/DCG data

• TX Power, TX Modulation Data

• Squelch Data

• Display Data ...etc.

Audio Processor (A3):

The Audio processor consists of a one -chip IC ac comm odating almost all of the audio functions. The audio functions are under control of the microcomputer in compliance with the function of the radio unit. The functions of the audio processor are as follows:

• T one Reject Filter

• Limiter Amplifier

• Volume and Modulation Level Control

• Post Limiter Filter

• Squelch Filter and Rectifier

• CG/DCG Encode/Decode Filter and Limiter

• D/A Converter and comparator

• OSC Circuit and Digital Interface for Microcomputer

All of these functions are made up of switched, capacitor filters, amplifiers and timing logic. The timing for this logic is derived from the 3.579545 MHz clock generator. The clock signal is also applied to the microcompu ter.

Audio Amplifier (A4 a nd A6):

The audio amplifier is located between the audio processor and the microphone or the speaker. Amplifier A6 provides pre-emphasis and amplification for transmit audio and de-emphasis for the receive audio. Amplifier A4 amplifies the output signal of A6 to the level adequate for driving the speaker and VDC audio outpu t.

Voltage Regula tor Circuits (A7, A9, Q2, Q3, Q10 and Q11):

Voltage Regulator Circuit A9 provides a regulated +2.5 VDC. Using the 2.5 VDC as a reference voltage, A9, Q2 and Q3, in combination, generate 5.4 VDC for the radio unit. The control Transistors Q10 and Q11 are used for currentlimiting to avoid break down.

External Data Buffer (A5):

The External Data Buffer is located between the UDC connector and the microcomputer for protection of the internal circuits.

Signaling Board

The Signaling Board consists of the following circuits:

• CMOS Microcomputer (A301)

• Audio Amplifier ( A302)

• Comparator (A303)

Microcomputer (A301):

The microcomputer provides various software for signaling

the radio unit as follows:

• Encoding the DTMF and GE Star

• Decoding the sequential Two Tone

• Providing control for SCAN operation

Audio Amplifie r (A30 2):

The audio amplifier is located between the audio processor and the microcomputer (A301). Amplifier (A302b and A3 02a) provides a Low Pass Filter, resistors R310-R312 and capacitors C303-C305, for tone encoding.

Comparator (A303):

The comparator converts the audio signal from the DISC output into a signal which can decode the microcomputer (A301).

LCD Board

The LCD board is composed of the following items:

• LCD Drive IC (A1)

• LCD

• Back Lighting Circuit (Q1, Q2 and CR1 - 6)

The LCD driver converts data from the microcomputer into a signal which can drive the LCD display. The LCD display is equipped wit h 8 character, 14 segments each and eight status displays. Microcomputer signals drive the LCD driver and the driver turns the LCD on. Al so this board has a back 1ighting circuit enabled upon receiving a signal from the microcomputer when any of the control switches (VOL, PTT, ...etc.) are operated.

Key Pad

The key pad, used with the standard M-PD Personal Radio, is located on the top of the housing. This key pad consists of

flexible cable and rubber contacts. The cable connects wi th t he microcomputer.

UDC Connector

The UDC connector is located on the side of the radio housing so that various kinds of external equipment connections can be made. External equipment connecting signals are as follows:

• TX Data

• RX Data

• CTS

• PTT

• EXT MIC

• RX Audio Out

• T/R

• Mute

• Disc Out

• +7.5 V olts

• Switch Out

• EMER

• UDC

The radio control microprocessor senses the value of voltage at the UDC line and switches the appropriate audio circuits to provide proper radio/ accessory operation. The UDC voltage is set by two resistors within the UDC connector.

For Data Loader

For External MIC

& SPKR

GE Star Lanyard

Battery Packs

The battery packs are available in three capacities: standard, high and extra high. All battery packs provide a nominal

7.5 Volt DC output.

To protect the battery pack from external short circuits, the positive (+) charging contact is diode protected.

An internal thermistor senses variations in battery pack temperature to automatically control a charger and provide a maximum charge without overheating the battery pack. All battery packs can be charged in one hour.

The battery is shipped fully charged to the custo mer, ready for use. However, if the battery pack is stored for any len gth of time it should be fully charged before placing into service.

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