Multitone BSR 113 Technical Manual

BSR 113

TM1194A Issue B Page (i)

TECHNICAL MANUAL

for

UHF BASE STATION RECEIVER

MODEL BSR 113

(448MHz)

Printed and published in England

BSR 113

TM1194A Issue BPage (ii)

COMPANY LIABILITY

The information in this manual has been carefull

y

compiled and checked for technical

accurac

y

. Multitone Electronics plc accept no liabilit

y

for inaccuracies or errors. In line

with the compan

y

polic

y

of technical advancement, the information within this document

ma

y

be chan

g

ed. The user should ensure that the correct issue of the document is

used. Comments or correspondence re

g

ardin

g

this manual should be addressed to:

Multitone Electronics plc

Technical Publications

Kimbell Road

Basin

g

stoke

Hampshire

RG22 4AD

En

g

land

ISSUE DATE

B February 1998

BSR 113

TM1194A Issue B Page (iii)

CONTENTS

Pa

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e

(

I

)

Title Pa

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e

Pa

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e

(

ii

)

Compan

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Liabilit

y

Pa

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e

(

iii

)

Contents

Pa

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(

iv

)

Effective Pa

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e List

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(

v

)

Safet

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Summar

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Warnin

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(

vi

)

Cautions

Section 1 Introduction and Specification

Section 2 Operatin

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Instructions

Section 3 Technical Description

Section 4 Installation and Commissionin

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Section 5 Servicin

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Section 6 Spare Parts List

Section 7 Dia

g

rams

BSR 113

TM1194A Issue BPage (iv)

EFFECTIVE PAGE LIST

Page No. Issue Page No. Issue Page No. Issue

(

I

)

B3-7B5-7B

(

ii

)

B3-8B5-8B

(

iii

)

B3-9B5-9B

(

iv

)

B 3-10 B 5-10 B

(

v

)

B4-1B5-11B

(

vi

)

B4-2B5-12B

1-1 B 4-3 B 5-13 B

1-2 B 4-4 B 5-14 B

1-3 B 4-5 B 6-1 B

1-4 B 4-6 B 6-2 B

1-5 B 4-7 B 6-3 B

1-6 B 4-8 B 6-4 B

2-1 B 4-9 B 6-5 B

2-2 B 4-10 B 6-6 B

3-1 B 5-1 B 7-1 B

3-2 B 5-2 B 7-2 B

3-3 B 5-3 B 7-3/4 B

3-4 B 5-4 B 7-5/6 B

3-5 B 5-5 B 7-7/8 B

3-6 B 5-6 B 7-9/10 B

7-11 B

BSR 113

TM1194A Issue B Page (v)

MANY RESINS AND OTHER CHEMICALS USED IN THE MANUFACTURE OF

ELECTRICAL COMPONENTS FITTED TO THIS BOARD GIVE OFF TOXIC FUMES

WHEN INCINERATED. APPROPRIATE PRECAUTIONS SHOULD THEREFORE BE

TAKEN WHEN DISPOSING OF THESE ITEMS.

SAFETY SUMMARY

The followin

g

information applies to both operatin

g

and servicin

g

personnel. General

Warnin

g

s and Cautions will be found throu

g

hout the manual where the

y

appl

y

.

WARNING statements identif

y

conditions or practices that could result in personal in

j

ur

y

or loss of life.

CAUTION statements identif

y

conditions or practices that could result in e

q

uipment

dama

g

e.

WARNING

BSR 113

TM1194A Issue BPage (vi)

CAUTIONS

DO NOT INSTALL THE RECEIVER WHERE IT MAY BE EXPOSED TO LIQUIDS,

STRONG MAGNETIC FIELDS, EXTREME TEMPERATURES OR STRONG SUNLIGHT.

STATIC SENSITIVE DEVICES ARE USED WITHIN THIS EQUIPMENT. CARE MUST

BE TAKEN TO ENSURE DAMAGE TO THESE DEVICES IS NOT CAUSED BY HIGH

LEVELS OF STATIC ELECTRICITY. SPARE BOARDS OR COMPONENTS SHOULD BE

STORED IN ANTI-STATIC PACKAGING WHEN NOT INSTALLED IN THE EQUIPMENT.

DIRECT CONNECTION OF THE BSR 113 TO PUBLIC TELEPHONE OPERATOR

(

PTO

)

LINES IS PROHIBITED UNLESS NATIONAL LINE CONNECTION APPROVAL HAS BEEN

GRANTED BY THE APPROPRIATE REGULATORY AUTHORITY.

UNDER NO CIRCUMSTANCES SHOULD SK1 BE CONNECTED TO THE SYSTEM BUS

OF MULTITONE ACCESS 1000 OR ACCESS 3000 SYSTEMS.

BSR 113

TM1194A Issue B Page 1 - 1

SECTION 1

INTRODUCTION AND SPECIFICATION

CONTENTS:

1. INTRODUCTION

2. FEATURES

3. PHYSICAL CONSTRUCTION

SPECIFICATIONS

4. Performance Characteristics

5. Power Supply

6. Connectors

7. Physical Characteristics

8. Operational Environment

FIGURE Page

1. Simplified BSR Configuration 1-2

_______________________

INTRODUCTION

1. The Base Station Receiver model BSR 113 is an UHF double superheterodyne

frequency modulated receiver, operating on a specified frequency within the range

448MHz to 449MHz. The BSR 113 is suitable for systems providing two-way

speech between a base control unit and mobile transceivers, and for systems

incorporating talkthrough between the mobile transceivers via the base control unit.

A simplified block diagram of a typical BSR 113 configuration is shown in Figure 1.

TRANSCEIVER

RECEIVER

STATION

BASE

TRANSMITTER

CONTROL

SYSTEM

TAG10500-2

(e.

g

. ACCESS 3000)

BSR 113

TM1194A Issue BPage 1 - 2

Figure 1: Simplified BSR Configuration

FEATURES

2. The BSR 113 has the following features:

Signal detect relay

600 audio line and tone drivers

Speaker with volume control

Ability to link with other receivers

PHYSICAL CONSTRUCTION

3. The BSR 113 consists of a single Printed Circuit Board (PCB) mounted in a tough,

moulded plastic outer casing, consisting of a base and a cover. The PCB is

mounted on the base and a loudspeaker is fitted to the cover. Connector sockets

are fitted to a cover plate at the rear of the unit. The speaker volume control is

also located at the rear of the unit. The BSR 113 can be wall or shelf mounted.

BSR 113

TM1194A Issue B Page 1 - 3

SPECIFICATIONS

Performance Characteristics

4. The performance characteristics of the BSR 113 are as follows:

a) Frequency Range: 448.0 - 449.0MHz

b) Suggested Frequencies: 1: 448.1250MHz

2: 448.1500MHz

3: 448.2250MHz

4: 448.3500MHz

5: 448.6750MHz

c) Channel Spacing: 25kHz

d) Intermediate Frequencies: 1st: 45MHz

2nd: 455kHz

e) Crystal Frequency (1st LO): ƒx = ƒc - 45MHz

6

f) Sub-Audio Tone Frequencies: 88.5Hz, 103.5Hz, 114.8Hz, 127.3Hz,

141.3Hz

g) Sub-Audio Tone Squelch: To EIA standard RS-220

h) Full System Deviation: ±5kHz for 20/25kHz channel spacing

j) Sensitivity (conducted): <1µV for 12dB SINAD at 60% of full

system deviation

k) Tone Squelch Sensitivity: <0.7µV at 15% of full system deviation

l) Adjacent Channel Rejection: >70dB Standard (2 signal method)

m) Spurious Response Rejection: >70dB (2 signal method)

n) Intermodulation Response

Rejection: >60dB (3 signal method)

p) Audio Output (Internal

Loudspeaker): 100mW into 8

BSR 113

TM1194A Issue BPage 1 - 4

q) Audio Output External Line Level: -13dBm nominal (-4dBm max) to 600

(internal, pre-set)

r) Radiated Power to Antenna: <2nW

s) Cabinet Radiation: <2nW

t) Signal Detect Relay Contact Rating: 100V DC, 250mA, non-inductive

Power Supply

5. The power supply requirements of the BSR 113 are as follows:

a) Power Supply: 12V DC

b) Current Consumption: <400mA maximum

Connectors

6. The BSR 113 is fitted with the following connectors:

a) SK2: Audio/Tone Out

b) SK1: Squelch Relay

c) SK3: DC Power Supply

d) SK7: Antenna

Physical Characteristics

7. The physical characteristics of the BSR 113 are as follows:

a) Overall Dimensions: Width: 235mm

Depth: 207mm

Height: 50mm

b) Weight: 0.7kg

BSR 113

TM1194A Issue B Page 1 - 5

Operational Environment

8. The environmental characteristics of the BSR 113 are as follows:

a) Operational Temperature Range: -25 C to +55 C

b) Humidity: Up to 95% Relative Humidity over the

operational temperature range

c) Stability: ±6ppm over the operational temperature

range

BSR 113

TM1194A Issue BPage 1 - 6

INTENTIONALLY BLANK

BSR 113

TM1194A Issue B Page 2 - 1

SECTION 2

OPERATING INSTRUCTIONS

CONTENTS:

1. OPERATION

_______________________

OPERATION

1. The BSR 113 is automatic in operation, with the exception of the following:

a) Switching on the power supply.

b) Setting the volume control (located at the rear of the unit) to a suitable level.

BSR 113

TM1194A Issue BPage 2 - 2

INTENTIONALLY BLANK

BSR 113

TM1194A Issue B Page 3 - 1

SECTION 3

TECHNICAL DESCRIPTION

CONTENTS:

1. INTRODUCTION

RADIO CIRCUITRY

2. Signal Input and Isolation

3. RF Amplifier and Filters

4. First Local Oscillator

6. First Mixer

7. Second Local Oscillator and Mixer

8. Second IF Stage

9. Audio Splitting

RX AUDIO PATH

10. Filtering and Amplification

11. Speaker Audio

12. Line Out Driver

NOISE SQUELCH PATH

15. Filtering and Amplification

18. Schmitt Monostable

20. Signal Logic Levels

21. Signal Indication and Noise Squelch Defeat

22. Signal Detect Reed Relay

23. Signal Strength Tone Circuitry

26. Tone Out Driver

SUB-AUDIO TONE PATH

29. Filtering and Amplification

30. Sub-Audio Tone Decoder

32. Sub-Audio Tone Indication and Disable

33. Sub-Audio Tone Squelch Delay Circuit

35. DATA PATH

POWER SUPPLIES

36. +12V Supply

37. +10V Regulator

38. +5V Regulator

39. +1V Internal Reference

BSR 113

TM1194A Issue BPage 3 - 2

TABLES Page

1. Noise Squelch Signal Levels 3-8

2. Sub-Audio Tone Frequency Adjustments 3-10

FIGURE

1. Functional Block Diagram 3-2

_______________________

INTRODUCTION

1. This section provides a technical description of the BSR 113 circuit operation.

Reference should be made to the functional block diagram (Figure 1) and the circuit

diagrams in Section 7.

RADIO CIRCUITRY

Signal Input and Isolation

2. The incoming RF signal is detected by an external antenna connected to

socket SK7, from where the signal passes through an isolating transformer (T1)

which improves immunity to Electro-Static Discharge (ESD). The signal is then fed

to the first RF helical filter, FL11, which protects the RF amplifier from strong out-of-

band signals.

RF Amplifier and Filters

3. Impedance matching is provided by L15, L16 and associated components. The RF

signal is amplified by TR3 and then filtered by the helical filters FL8, FL9 and FL10.

They provide a degree of selectivity before passing the signal to the first mixer.

First Local Oscillator

4. The first local oscillator comprises TR1, XL1 and associated components.

Frequency adjustment is provided by C3. The collector of TR1 is tuned to the third

harmonic of XL1 by C9 and L6. The output of TR1 is then doubled by TR2 to

provide the correct injection frequency for the first mixer.

5. The frequency of the crystal is calculated by using the following formula:

Crystal (XL1) frequency (MHz) = Receiver Channel Frequency (MHz) - 45MHz

6

BSR 113

TM1194A Issue B Page 3 - 3

Figure 1: Functional Block Diagram

BSR 113

TM1194A Issue BPage 3 - 4

First Mixer

6. The first mixer comprises TR6 and associated components. The injection frequency

from the first local oscillator is fed to the first mixer via the helical filter FL7 and

inductor L9. The RF signal is input via the inductor L13. The difference signal of

45MHz is selected by the collector load of L12, R18 and C29. The 45MHz is then

filtered by FL1 and FL2 to remove unwanted signals.

Second Local Oscillator and Mixer

7. The second local oscillator is formed by TR4, XL2 and associated components. It

runs at a fixed frequency of 44.545MHz. The signal is selected from the collector

of TR4 and input, along with the RF from FL2, onto the base of mixer TR5. The

difference signal of 455kHz then passes to FL5, with matching provided by R31.

Second IF Stage

8. The second IF chain comprises three ceramic filters of channel bandwidth, FL5, FL6

and FL4, each followed by an IF amplifier. After FL5 the 455kHz IF signal is

amplified by the low noise transistor TR25 and then passed to FL6. The signal is

then fed to IC1 (pin 1) where the remaining IF amplification and amplitude limiting

are provided. Another stage of filtering is carried out by FL4. Demodulation is

carried out using the ceramic discriminator FL3 as the quadrature network for the

on-chip demodulator. After demodulation the signal is output from IC1 (pin 14).

Audio Splitting

9. The demodulated audio signal leaves IC1 (pin 14) and divides three ways:

a) To a de-emphasis circuit (comprising R339 and C104) and the Rx Audio path.

b) To a de-emphasis circuit (comprising R365 and C154) and the Noise Squelch

path.

c) To an active filter (comprising TR24, C82, C83, R341 and R344) where it then

divides two ways:

i) To the Sub-Audio Tone path.

ii) To the Data path.

BSR 113

TM1194A Issue B Page 3 - 5

RX AUDIO PATH

Filtering and Amplification

10. The audio signal is de-emphasised by R339 and C104 to produce the test and tune

up signal Audio X (available at the internal test socket SK5 pin 2). It also passes

through two stages of high pass filtering and two stages of low pass filtering,

provided by IC11 (pin 8) and IC11 (pin 14), to become the Rx Audio signal. The

fitting of link LK4 enables the signal to bypass the high pass filter stage IC11 (pin

1) (for future applications). IC11 (pin 7) acts as a buffer amplifier.

Speaker Audio

11. The Rx Audio output from IC11 (pin 14) is fed, via the audio gate TR13, to the

input of an operational-amplifier circuit, IC10, via R93 and RV4. Variable resistor

RV4 provides volume control. The speaker driver uses a bridge technique to

provide maximum voltage swing on the speaker driver output. Resistors R168,

R169, R170 and R171 are load protection for IC10 to prevent any damage to the

chip resulting from over dissipation.

Line Out Driver

12. The Rx Audio output from IC11 (pin 14) is also fed, via the audio gate TR23 and

RV6, to the Line Out driver amplifier IC8. In normal operation link LK2 is fitted and

the Line Out signal is gated by the noise Squelch, via gate TR18. Alternatively, the

signal can be continuously enabled by removing link LK2.

13. The output of IC8 (pin 1) is passed to the line termination loading and safety barrier

circuitry provided by components R104, R105, R106, R107, R108, R109, C242,

C243, C244, CS4 and T4. The Line Out signal then proceeds to the external line

connection via SK2 (pins 4 and 6).

14. The links LK22, LK23, LK24, and LK25 are intended for setting the Line Out

termination loading when connecting to Public Telephone Operator (PTO) lines in

different countries (subject to national line connection approval). For further details

refer to Section 4. In normal operation Link LK5 is fitted and is removed only for

factory test purposes. The Tone Out signal is combined with the Line Out signal

by the fitting of link LK10 (refer to Section 4).

BSR 113

TM1194A Issue BPage 3 - 6

NOISE SQUELCH PATH

Filtering and Amplification

15. The audio signal from IC1 (pin 14) is de-emphasised by R365 and C154. It is then

filtered by the active filter stages TR41 and TR44 to pass only frequencies above

approximately 6kHz. These stages give approximately 60dBs of rejection of low

frequency audio relative to the high audio frequencies used by the squelch circuitry.

Adjustment of the noise Squelch signal is provided by RV2.

16. From the active filtering stages the audio is amplified by the successive stages

TR40, TR39 and TR38 to produce a high level noise signal at the collector of

TR38. All of these stages are designed to have very stable gain and frequency

response over the operational temperature range.

17. After passing through C163 the signal is fed to the final gain stage TR42, TR43,

which has been configured to have a very stable DC operating point so that the

peak-to-peak noise on the output is very stable with temperature change. The

resulting high level signal is then rectified and buffered by D9, TR37 and TR28,

again with special care being taken of temperature performance. The rectified

signal is smoothed by C167.

Schmitt Monostable

18. The following stage (comprising TR45, TR46, TR47, TR48, TR49 and TR50) is

configured as a Schmitt monostable. When the DC level goes above the level

determined by R373 and R414, then TR36 and TR47 are turned on thus holding

TR45 on and providing hysteresis. As the DC level decreases again R417 stops

TR45 turning off until a lower level is reached than that required to turn it on.

When TR36 collector goes low (i.e. during high noise/low Rx signal strength

conditions), TR48 turns on charging C106 and turning off TR49. This then turns

off TR50 and produces the noise Squelch signal on the collector of TR50.

19. The high levels of amplification are required to enable the noise Squelch to work

on strong RF signals where there is a great deal of quieting. This ensures that

sub-standard audio signals are not output to the system.

Signal Logic Levels

20. The time constants provided by C106 and R420 ensure that the audio is not

enabled until the carrier has been detected for more than approximately 50ms. This

ensures the minimum of squelch bounce in noisy conditions. The logic levels at the

collector of TR50 for the noise Squelch signal are as shown in Table 1.

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Multitone BSR 113 Technical Manual

Multitone BSR 113 Technical Manual

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