PYE Beaver M254 User manual

Service Manual
Pye Telecommunications Ltd
Beaver
VHF FM Mobile
Radiotelephone
Types M254 & M256
Publication Ref No.TP271

WARNING
Certain semiconductor devices used in this equipment con-
tain Beryllium Oxide. If inhaled, dust from this oxide can
be toxic.
No danger can arise from normal handling but no attempt
should be made to tamper with these devices.
They should not be discarded with industrial or domestic
waste.
This service manual is for the maintenance of Pye Telecommunications equipment.
The performance figures quoted are typical and are subject to normal manufacturing and
service tolerances.
The right is reserved to alter the equipment described in this manual in the light of future
technical development.
BEAVER
VHF FM MOBILE RADIOTELEPHONE
TYPES M254 AND M256
SERVICE MANUAL
ISSUE 1 MARCH 1976
E TELECOMMUNICATIONS LIMITED

CAMBRIDGE

ENGLAND
nted in England

©1976

TP271

AMENDMENT LIST
Changes made to the equipment described in this publication are published as amendments
which are dated and consecutively numbered.
Reprints will incorporate all the amendments to date and an entry to this effect will be recorded
on the amendment list below. Each page affected by amendment action will bear the amendment
number as a suffix to the reference number eg TP123/4 indicates that the page has been corrected by
amendment number 4.
Should it be necessary to raise the issue of a publication the amendment numbering will
recommence with No. 1.
Amend't No.
Date
Initials
Remarks
1
October 1978
Incorporated on Reprint
ERRORS & OMISSIONS
The usefulness of this publication depends upon its accuracy. Whilst every endeavour has been
made to minimise errors, some may exist. It is therefore requested that any errors or omissions noted
be advised as follows:—
Please quote:
a) Title of publication
b)
TP No. and issue No.
c)
Last amendment No. received
d)
Page and/or Fig. No. in error
Please send to.
Pye Telecommunications Ltd.
Publications Dept.
Mariners Way
Cambridge CB4 1 BN
England

CONTENTS
Page
SECTION 1

GENERAL INFORMATION
Summary of Data 
1.1
Introduction 
1.3
Equipment Variations

1.4
Module Identification

1.5
SECTION 2

INSTALLATION AND OPERATION
Pre-Installation Checks 
2.1
Netting Procedures 
2.2
Test Frequency Crystal Information

2.2
Contents List (Installation Items)

2.2
Installation Procedure 
2.3
Antenna Information 
2.12
Operation 
2.14
SECTION 3 
TECHNICAL DESCRIPTION
Receiver Circuit Summary

3.1
Transmitter Circuit Summary

3.2
Power Distribution and Switching

3.3
12,5V Restrictor and 10V Regulator

3.4
Control Panel (Front Mount)

3.4
Control Unit (Remote Mount)

3.4
RF Front End

3.6
Oscillator Modules
12-channel Oscillator

3.7
Single Channel Oscillator

3.8
6-channel Oscillator

3.9
PA Module

3.10
Antenna Filter and Changeover Relay

3.10
Receiver Oscillator Multiplier

3.12
Transmitter Exciter

3.12
IF Amplifier and Squelch

3.15
Transceiver Audio (Receiver Part)

3.16
Transceiver Audio (Transmitter Part)

3.17
TP271/1

CONTENTS (Continued)
Page
SECTION 4

SERVICING
PRECAUTIONS AND GENERAL INFORMATION
Routine Frequency Adjustment

4.1
'Pozidriv' Screws

4.1
Griplets

4.1
Component Removal From PWBs Fitted with Griplets

4.1
Servicing Compounds

4.1
Soldering

4.1
Printed Wiring Boards

4.2
Replacement of Plug-in Modules

4.2
Use of FM Beaver Test (Extension)
Assemblies Kit

4.2
Fault Finding - Integrated Circuits
(IC's) and Thick Film Circuits (TFs)

4.2
Antenna Loading

4.2
CONSTRUCTION

4.4
EQUIPMENT ACCESS 
4.5
Tools Required 
4.5
Procedure 
4.5
Module Replacement 
4.6
TEST EQUIPMENT

4.8
CRYSTAL INFORMATION
 4.9
ALIGNMENT PROCEDURE AND PERFORMANCE CHECKS
Test Points (TPs)

4.9
Measuring Points (MPs)

4.9
Identification of Modules and Components

4.10
Signal Generator Levels

4.10
Intermediate Frequencies

4.10
Multiple Channel Equipments

4.10
Multi meter

4.10
General Preliminary Checks and Adjustments

4.10
Receiver Alignment

4.10
Transmitter Alignment

4.12
CHANGE OF FREQUENCY PROCEDURE

4.14
RECEIVER PERFORMANCE CHECKS
 4.14
RF Sensitivity 
4.14
Audio Sensitivity 
4.14
Audio Power Output 
4.14
Bandwidth 
4.14
Squelch 
4.14
Frequency Count 
4.15
Sinad Measurement 
4.15
TP271/1

CONTENTS (Continued)
Page
TRANSMITTER PERFORMANCE CHECKS
Power Output

4.15
Supply Voltage

4.15
Frequency Check

4.15
Peak Deviation

4.16
SINGLE TO MULTICHANNEL CONVERSION

4.17
SECTION 5
 PARTS LIST
Notation  5.1
Ordering of Spare Parts  5.1
Abbreviations  5.1
Front Mount Radiotelephone Type M254
Complete including optional motorcycle Mounting

5.2
Front Mount Transceiver Type M254  5.4
Remote Mount Radiotelephone Type M256 Complete  5.7
Remote Mount Transceiver Type M256  5.10
RF Front End Module (1)  5.11
IF Amplifier and Squelch Module (2)

5.13
Squelch 'A' Sub-module (2A)  5.14
Receiver and Transmitter Oscillator Module (3)

5.15
Receiver Oscillator Multiplier Module (4) 
5.16
12,5V Restrictor and 10V Regulator Module (6)

5.18
Transceiver Audio Module (7)  5.19
Transmitter Exciter Module (8)

5.22
Transmitter Power Amplifier Module (9) 
5.24
Antenna Filter and Changeover Relay Module (10) 
5.25
Mother Board Assembly (11)

5.26
Control Interface Assembly (13) 
5.26
SECTION 6 
DIAGRAMS
TP271/1

LIST OF ILLUSTRATIONS
Page
Fig. 2.1

Typical Installation (Front Mount)
 2.5
Fig. 2.2 
Basic Installation (Front & Remote Mount)
 2.9
Fig. 2.3 
Basic Installation - Motorcycle 
2.10
Fig. 3.1

Receiver Block Diagram 
3.1
Fig. 3.2 
Transmitter Block Diagram 
3.2
Fig. 3.3 
Power Supply Block Diagram

3.3
Fig. 4.1
 Test (Extension) Assemblies 
4.3
Fig. 4.2 
Mechanical Construction 
4.4
Fig. 4.3 
Facility Socket Interconnections

4.7
Fig. 4.4

Diode Probe Circuit Diagram  4.8
Fig. 4.5 
Connection of AF Output Meter

4.8
Fig. 5.1
 Eploded Diagram

5.23
Fig. 6.1 
Complete Mother Board Layout
Fig. 6.2

Receiver Circuit Diagram
Fig. 6.3

Transmitter Circuit Diagram
Fig. 6.4 
Receiver - Earlier Modules and Component Layout Diagram
Fig. 6.5 
Transmitter - Earlier Modules and Component Layout Diagram
Fig. 6.6

Transceiver Overall Circuit Diagram (Earlier Modules)
Fig. 6.7 
Remote Mount Interface & Control Units
Fig. 6.8 
Transmitter Exciter A & B Bands
Fig. 6.9

Front Mount Control Panel
TP271/1

SECTION 1
GENERAL INFORMATION
Channel Spacing
No. of Channels
Switching Bandwidth
Equipment Operating Temperature
Range
Frequency Stabilitiy
Power Supply
Current Consumption
Operator Controls
Indicator Lamps
Overall Dimensions
Single or two-frequency simplex
Frequency (phase)
Band A 148-174 MHz
Band B 132-156 MHz
Band E

68-88 MHz
12,5 kHz —

S
20 kHz —
25 kHz — V
Single Channel
Up to 6 Channels
Up to 12 Channels
±0,5% mean operating frequency
—30°C to + 60°C ambient
Stabilities are available to meet climatic and mandatory
requirements up to ±0,0005% over the temperature range
—30°C to +60°C
12V (nominal) DC supply, positive, negative or floating
ground. 24V operation available by separate regulator
unit.
Receive (standby): M254 360mA approx.
M256 440mA approx.
Transmit: 4,25A
On-Off switch, Squelch
Volume, Channel selector
*Reset/Lock/Defeat Switch
Power on (also illuminates channel selector and volume
control)
Transmit:  *Call Lamp
Main Unit:  198mm wide x 93mm high (includes
(M254)  mounting plate) x 241mm deep
(7,8 x 3,6 x 9,5 in)
Main Unit:  198mm wide x 93mm high (includes
(M256)  mounting plate) x 222mm deep
(7,8 x 3,6 x 8,7 in)
Speaker Unit: 1. Weatherproof flat circular 215mm x
178mm x 102mm (8,5 x 7 x 4 in)
2. Weatherproof Re-entrant Horn 127mm
x 50mm x 76mm (5 x 2 x 3 in)
Control Unit 201mm wide x 85mm high x 84mm
deep (across projections)
(7,9 x 3,3 x 3,3 in)
*Used only with Selective Call Module
SUMMARY OF DATA
General
Operation
Modulation
Frequency Bands

Summary of data (Contd.)
Finish
Optional Extras
Receiver
Input Impedance
Sensitivity
Signal/Noise
Audio Output
Audio Response
I ntermodulation Attenuation
Spurious Response Attehuation
Squelch
Main Unit 
die cast aluminium finished in yellow
and Control Unit: with black polycarbonate front
panel
Speaker Unit. 
Yellow
(i)
2-12 channels
(ii) 24V regulator — VR 200
(iii)
RF power amplifier — A200 (12V DC supplies only)
(iv)
Choice of antennas
(v)
Selection of Selective Call modules (Details on
application)
(vi) Choice of frequency stabilities
(vii)
Telephone handset in place of fist microphone
(viii)
Adjustable Transmitter Power Module
(ix)
Choice of either circular bulkhead or re-entrant
horn loudspeaker (both weatherproof)
5052
20 db quieting for 0,35W PD signal input
12 db SINAD for 0,250V PD signal input
M254 3,0W with less than 5% distortion at 1 kHz
M256 2,5W with less than 5% distortion at 1 kHz
+1 db to —3 db of a 6 db per octave de-emphasis
characteristic from 300 Hz to 3 kHz
70 db
85 db
6 db quieting at threshold. Sensitivity adjustable
Transmitter
Output Impedance

50Ct
Power Output

15W minimum (at 13,8V DC input)
(Adjustable down to 5W as required 25-50W available
with separate power amplifier
Spurious Outputs

Harmonics 2,5 oW at antenna socket. Other outputs
0,25 oW at antenna socket.
Modulation

+1 db to —3 db of 6 db per octave pre-emphasis
characteristic from 300 Hz to 3 kHz
Modulation Distortion

Less than 5% at 1 kHz with 60% deviation
Typical figures based on normal operating conditions. Pye policy is one of continuous improvement
therefore the right is reserved to change specifications without notice.
1.2

INTRODUCTION
1.
The Beaver is a frequency modulated VHF mobile radiotelephone designed for two-way
communication between mobiles and a base station.
2.
Two versions of the equipment are available, type M254 (Front Mount) and type M256
(Remote Mount)' Both types employ similar ruggedised transceivers (featuring plug-in
modules) together with one of the two loudspeakers available and either a fist microphone
or handset. All items of the installation are weatherproof. The only physical difference
between the M254 and M256 is that the control panel of M254 is integral with the transceiver
while that of the M256 is contained in a separate control unit and connected to the
transceiver through a control cable.
3.
It operates on fixed crystal controlled frequencies in the range 68 to 174 MHz using either
single or two-frequency simplex working.
4.
Single and multiple channel versions are available; in multiple channel equipments provision is
made for up to 12 communication channels spaced at 12,5 kHz, 20 kHz or 25 kHz within
.±0,5% of the centre frequency. The channel spacing can be changed by replacing the IF
Amplifier and Squelch Module.
5.
The transmitter generates a modulated carrier of 15 watts into a 50Q load; an add-on RF
amplifier (Pye Type A200) is available which increases the output to 50 watts.
6.
The receiver delivers 3 watts (M254) or 2,5 Watts (M256) audio with less than 5% distortion
into a 3Q load.
7.
The power supply is normally 12V DC nominal but a 24/12V voltage regulator unit (Pye
Type VR200) is available for use with 24V DC systems.
8.
Space provision is made within the transceiver for any one of a range of Pye selective
signalling facilities.
1.3