Tait TEL0060, TEL0059 Users Manual

M800 SL2 CI

Part C T854 Transmitter

This part of the manual is divided into six sections, as listed below. There is a detailed
table of contents at the start of each section.

Section Title

1 General Information

2 Circuit Operation

3 Initial Tuning & Adjustment

4 Functional Testing

5 Fault Finding

6 PCB Information

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CII M800 SL2

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M800 SL2 T854 General Information C1.1

1 T854 General Information

This section provides a brief description of the T854 transmitter, along with detailed
specifications and a list of types available.

The following topics are covered in this section.

Section Title Page

1.1 Introduction 1.7

1.2

1.2.1

1.2.2

1.2.3

1.2.4

1.2.4.1

1.2.4.2

1.2.4.3

1.2.5

1.2.6

1.2.6.1

1.2.6.2

1.2.6.3

1.3 Product Codes 1.13

1.4 T854 Standard Product Range 1.14

Specifications

Introduction
General
RF Section
Audio Processor

Inputs
Modulation Characteristics
CTCSS

Microcontroller
Test Standards

European Telecommunication Standard
DTI CEPT Recommendation T/R-24-01
Telecommunications Industry Association

1.8

1.8

1.8

1.9

1.10

1.10

1.11

1.11

1.11

1.12

1.12

1.12

1.12

Figure Title Page

1.1 T854 Main Circuit Block Identification 1.4

1.2 T854 Front Panel Controls 1.4

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C1.2 T854 General Information M800 SL2

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M800 SL2 T854 General Information C1.3

Figure 1.1 T854 Main Circuit Block Identification

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8500C1xx.fm

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C1.4 T854 General Information M800 SL2

Figure 1.2 T854 Front Panel Controls

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8500C1xx.fm

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M800 SL2 T854 General Information C1.5

1.1 Introduction

The T854 is a synthesised, microprocessor controlled FM base station transmitter
designed for single or multichannel operation in the 400 to 520MHz frequency range
with a standard power output of 25W. The RF section of the transmitter comprises a fre­quency synthesiser which provides 100mW of frequency modulated RF drive to a two
stage, wide band output driver followed by a 25W power supply. A thermal shutdown
feature is provided in the T854 in case operating temperatures exceed acceptable levels.
The T854 is rated for continuous operation.

The T854 is rated for a continuous output power of 25W at +60°C. This is achieved via a
high capacity heatsink, electric fan and shroud. The fan draws air across the heatsink to
dissipate the heat. The heatsink replaces one of the usual T800 covers.

A wide selection of audio characteristics may be obtained from the audio processor.
Optional circuit blocks are an audio compressor and a pre-emphasis stage. They can be
bypassed or linked to one or both audio inputs, and then back into the remaining audio
circuitry in almost any combination. All audio processor options are link selectable.

The synthesiser frequency is programmed via the serial communications port. Eight
channel select lines are accessible via an optional D-range connector (D-range 2 ­T800-03-0000) at the rear of the set.

All components except those of the VCO are mounted on a single PCB. This is secured
to a die-cast chassis which is divided into compartments to individually shield each sec­tion of circuitry. Access to the PCB is primarily through the top cover of the radio, as all
components are mounted on the top side of the PCB. There is provision within the chas­sis to mount small option PCBs.

1

The front panel controls include line sensitivity, microphone socket and carrier switch.
This switch turns on the carrier (unmodulated) as an aid to servicing.

The T854 is designed to be part of the slimline frame.

1. Although capable of operating over the 400-520MHz frequency range, the T854 and
T857 have an 8MHz switching range (see Section 1.2.3 and Section 3.1).

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C1.6 T854 General Information M800 SL2

1.2 Specifications

1.2.1 Introduction

The performance figures given are minimum figures, unless otherwise indicated, for
equipment tuned with the maximum switching range and operating at standard room
temperature (+22°C to +28°C) and standard test voltage (13.8V DC).

Where applicable, the test methods used to obtain the following performance figures
are those described in the EIA and ETS specifications. However, there are several
parameters for which performance according to the CEPT specification is given. Refer
to Section 1.2.6 for details of test standards.

Details of test methods and the conditions which apply for Type Approval testing in all
countries can be obtained from Tait Electronics Ltd.

The terms "wide bandwidth", "mid bandwidth" and "narrow bandwidth" used in this
and following sections are defined in the following table.

Channel Spacing

Wide Bandwidth 25kHz ±5.0kHz 15.0kHz

Mid Bandwidth 20kHz ±4.0kHz 12.0kHz

Narrow Bandwidth 12.5kHz ±2.5kHz 7.5kHz

Modulation

100% Deviation

Receiver

IF Bandwidth

1.2.2 General

Number Of Channels .. 128 (standard)

Supply Voltage:

Operating Voltage .. 10.8 to 16V DC
Standard Test Voltage .. 13.8V DC
Polarity .. negative earth only
Polarity Protection .. crowbar diode
Line Keying Supply (if required) .. -50V DC

Supply Current:

1

Transmit - T854 .. 5.5A (typical)
Standby - T854 .. 165mA (typical)

Operating Temperature Range .. -20°C to +60°C

1. Additional channels may be factory programmed. Contact your nearest Tait Dealer or
Customer Service Organisation.

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M800 SL2 T854 General Information C1.7

Overall Dimensions:

Height .. 132mm
Width .. 480mm
Depth .. 335mm

Weight with Tone Remote .. 16kg
Weight without Tone Remote .. 13kg

Time-Out Timer (optional) .. 0 to 5 minutes

1

adjustable in 10 sec-

ond steps

Tail Timer .. 0 to 5 seconds adjustable in 100ms

2

steps

Transmit Key Time .. <30ms

Transmit Lockout Timer .. 0 to 1 minute adjustable in 10 second

steps

1.2.3 RF Section

Frequency Range .. 400-520MHz (refer to Section 1.4 and

Section 1.5)

Modulation Type .. FM

Frequency Increment .. 5 or 6.25kHz

Switching Range .. 8MHz (i.e. ±4MHz from the centre

frequency)

Load Impedance .. 50 ohms

Frequency Stability .. ±1ppm, -20°C to +60°C
(see also Section 1.4 and Section 1.5)

Adjacent Channel Power (full deviation):

Wide Bandwidth (WB) .. -75dBc
(±25kHz/15kHz B/W)

Mid Bandwidth (MB) .. -70dBc
(±20kHz/12kHz B/W)

Narrow Bandwidth (NB) .. -65dBc
(±12.5kHz/7.5kHz B/W)

Transmitter Switching .. complies with ETS 300 113

1. Adjustable from 0 to 10 minutes in PGM800Win version 2.12 and later.

2. Adjustable in 20ms steps in PGM800Win version 2.12 and later.

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C1.8 T854 General Information M800 SL2

Transmitter Side Band Noise:
(no modulation, 15kHz bandwidth)

At ±25kHz .. -95dBc
At ±1MHz .. -105dBc

Intermodulation .. -40dBc with interfering signal of

-30dBc

.. -70dBc with 25dB isolation

& interfering signal of -30dBc
(PA with output isolator)

T854 Mismatch Capability:

Ruggedness .. refer to your nearest Tait Dealer or

Customer Service Organisation

Stability .. 3:1 VSWR (all phase angles)

Radiated Spurious Emissions:

Transmit .. -36dBm to 1GHz

-30dBm 1GHz to 4GHz

Standby .. -57dBm to 1GHz

-47dBm 1GHz to 4GHz

Conducted Spurious Emissions: (T854 Only)

Transmit .. -36dBm to 1GHz

-30dBm 1GHz to 4GHz

Standby .. -57dBm to 1GHz

-47dBm 1GHz to 4GHz

Power Output:

T854 - Rated Power .. 25W (see Duty Cycle)

- Range Of Adjustment .. 5-25W

Duty Cycle.. 100% @ 25W at +60°C

1.2.4 Audio Processor

1.2.4.1 Inputs

Inputs Available .. line, microphone and CTCSS

Line Input:

Impedance .. 600 ohms (balanced)
Sensitivity (60% modulation @ 1kHz)-

With Compressor .. -50dBm
Without Compressor .. -30dBm

Microphone Input:

Impedance .. 600 ohms

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M800 SL2 T854 General Information C1.9

Sensitivity (60% modulation @ 1kHz)-

With Compressor .. -70dBm
Without Compressor .. -50dBm

1.2.4.2 Modulation Characteristics

Frequency Response .. flat or pre-emphasised (optional)
(below limiting)

Line And Microphone Inputs:

Pre-emphasised Response-

Bandwidth .. 300Hz to 3kHz (WB & MB)

.. 300Hz to 2.55kHz (NB)

Below Limiting .. within +1, -3dB of a 6dB/octave

pre-emphasis characteristic

Flat Response .. within +1, -2dB of output at 1kHz

Above Limiting Response .. within +1, -2dB of a flat response

(ref. 1kHz)

Distortion .. 2% max.

Hum And Noise:

Wide Bandwidth .. -55dB (300Hz to 3kHz [EIA]) typical
Mid Bandwidth .. -54dB (CEPT)
Narrow Bandwidth .. -50dB (CEPT)

Compressor (optional):

Attack Time .. 10ms
Decay Time .. 800ms
Range .. 50dB

1.2.4.3 CTCSS

Standard Tones .. all 37 EIA group A, B and C tones

plus 13 commonly used tones

Frequency Error .. 0.08% max.
(from EIA tones)

Generated Tone Distortion .. 1.2% max.

Generated Tone Flatness .. flat across 67 to 250.3Hz to within 1dB

Modulation Level .. adjustable

Modulated Distortion .. <5%

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C1.10 T854 General Information M800 SL2

1.2.5 Microcontroller

Auxiliary Ports:

Open Drain Type .. capable of sinking 2.25mA via 2k2Ω

max. .. 5V

V

ds

1.2.6 Test Standards

Where applicable, this equipment is tested in accordance with the following standards.

1.2.6.1 European Telecommunication Standard

ETS 300 086 January 1991

Radio equipment and systems; land mobile service; technical characteristics and test
conditions for radio equipment with an internal or external RF connector intended pri­marily for analogue speech.

ETS 300 113 March 1996

Radio equipment and systems; land mobile service; technical characteristics and test
conditions for radio equipment intended for the transmission of data (and speech) and
having an antenna connector.

ETS 300 219 October 1993

Radio equipment and systems; land mobile service; technical characteristics and test
conditions for radio equipment transmitting signals to initiate a specific response in the
receiver.

ETS 300 279 February 1996

Radio equipment and systems; electromagnetic compatibility (EMC) standard for pri­vate land mobile radio (PMR) and ancillary equipment (speech and/or non-speech).

1.2.6.2 DTI CEPT Recommendation T/R-24-01

Annex I: 1988

Technical characteristics and test conditions for radio equipment in the land mobile
service intended primarily for analogue speech.

Annex II: 1988

Technical characteristics of radio equipment in the land mobile service with regard to
quality and stability of transmission.

1.2.6.3 Telecommunications Industry Association

ANSI/TIA/EIA-603-1992

Land mobile FM or PM communications equipment measurement and performance
standards.

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M800 SL2 T854 General Information C1.11

1.3 Product Codes

The three groups of digits in the T850 Series II product code provide information about
the model, type and options fitted, according to the conventions described below. Con­sult your nearest Tait Dealer or Customer Service Organisation for more information
regarding the availability of specific models, types and options.

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C1.12 T854 General Information M800 SL2

1.4 T854 Standard Product Range

The following table lists the range of standard T854 types (i.e. no options fitted) availa­ble at the time this manual was published. Consult your nearest Tait Dealer or Cus­tomer Service Organisation for more information.

Frequency Range (MHz) 400-440

Deviation (kHz) 2.5 2.5 4 5

TCXO ±1ppm -20°C to +60°C

Transmitter Type: T854- 16-0000

Frequency Range (MHz) 440-480

Deviation (kHz) 2.5 2.5 4 5

TCXO ±1ppm -20°C to +60°C

Transmitter Type: T854- 26-0000

Frequency Range (MHz) 480-520

Deviation 2.5 2.5 5

TXCO ±1ppm -20° to +60°C

Transmitter Type: T854- 36-0000

a. United States market only.

••••

a

15-0000 13-0000 10-0000

••••

a

25-0000 23-0000 20-0000

•••

a

35-0000 30-0000

Caution: T854-1X-XXXX Product Types

The 406 to 406.1MHz frequency range is reserved worldwide for use by
Distress Beacons. Do

not program transmitters to operate in this fre-

quency range.

You can identify the transmitter type by checking the product code printed on a label on
the rear of the chassis (Figure 1.1 in Part A shows typical labels). You can further verify
the transmitter type by checking the placement of an SMD resistor in the table that is
screen printed onto the PCB (refer to Section 6.1 for more details).

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M800 SL2 T854 General Information C1.13

T800 SL BSM Conventional Ordering Number System

System

Type

L A 1 W B 0 0

L = T800 SL BSM (T800-56-X0XX)

A =

66 - 88

B =

136 - 156

C =

148 - 174

D =

400 - 440

E =

440 - 480

F =

480 - 560

P =

800 - 870

Q =

860 - 910

*

R =

890 - 960

= Not Available for US Market

*

1

Frequency

MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz

Band

2

(T82x-xx-02xx)
(T83x-1x-02xx)
(T83x-2x-02xx)
(T85x-1x-02xx)
(T85x-2x-02xx)
(T85x-3x-02xx)
(T88x-1x-02xx)
(T88x-2x-02xx)
(T88x-3x-02xx)

RF Output

Power

1

2

Channel
Spacing

3

4

0 =
4 =

7

6 =
7 =
8 =
9 =

0 =
1 =
2 =

If Duplexer item code is set to (1), then Base/Repeater/

6

Slimline Requirement sheet must be completed. This is
required so correct Duplexer Frequency and Spacing can be
calculated.

Power

Supply

No Ancillary Option
Multi-Channel Option (10 CH)
Cabinet Desktop 3U (Blk)
Cabinet Desktop 4U (Blk)
Cabinet Transportable 6U (Blk)
Tone Remote Module

No Duplexer Fitted
50 Watt Duplexer Kit (T991-09-0001)+(T993-XX)
Coaxial Relay Kit (T800-09-0002)

Coaxial
Relay /

Duplexer

5

3/13/02

Ancillary

Options

67

(T992-03-0002)
(T992-04-0002)
(T992-06-0002)
(T803-00-0000)

1 =

25 Watts

4 =

5 Watts

*5 =

25 Watts (Cont)

* Only Available in Frequency

Bands

400-560Mhz

3

T991-09-0001 is a 1U 19" Tray for Duplexer fitting.

B =

5

4

BSM Kit with Power Supply

D =

BSM Kit with External DC

N =

12.5 kHz

M =

20 kHz

W =

25 kHz

(T800-56-X0X2)
(T800-56-X0X4)

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C1.14 T854 General Information M800 SL2

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M800 SL2 T854 General Information C1.15

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C1.16 T854 General Information M800 SL2

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M800 SL2 T854 Circuit Operation C2.1

2 T854 Circuit Operation

This section provides a basic description of the circuit operation of the T854 transmitter.

Note: Unless otherwise specified, the term "PGM800Win" used in this and follow-

ing sections refers to version 3.00 and later of the software.

Refer to Section 6 where the parts lists, grid reference index and diagrams will provide
detailed information on identifying and locating components and test points on the
main PCB. The parts list and diagrams for the VCO PCB are in Part E.

The following topics are covered in this section.

Section Title Page

2.1 Introduction 2.3

2.2 Microcontroller 2.4

2.3

2.3.1

2.4

2.4.1

2.5

2.5.1

2.5.2

2.5.3

2.5.4

2.5.5

2.6 Power Supply & Regulator Circuits 2.10

2.7 Transmit Timers 2.11

2.8 T854 Drive Amplifier & PA 2.12

Synthesised Local Oscillator

Two Point Modulation

VCO

VCO Supply

Audio Processor

General
Audio Inputs
Keying Inputs
Compressor (Automatic Level Control (ALC))
Outputs To Modulators

2.5

2.6

2.7

2.7

2.8

2.8

2.8

2.9

2.9

2.9

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C2.2 T854 Circuit Operation M800 SL2

Figure Title Page

2.1

2.3

2.4

2.5

2.6

2.7

2.8

T854 High Level Block Diagram
T854 Microcontroller Block Diagram
T854 Synthesiser Block Diagram
T854 Two Point Modulation
T854 Audio Processor Block Diagram
T854 Power Supply & Regulators Block Diagram
T854 Transmit Timers

2.3

2.4

2.5

2.6

2.8

2.10

2.11

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M800 SL2 T854 Circuit Operation C2.3

2.1 Introduction

The individual circuit blocks which make up the T854 are:

• synthesiser

• VCO

• audio processor

• drive amplifier

• voltage regulators.

Each of these circuit blocks is set in its own shielded compartment, formed as an inte­gral part of the main chassis.

The configuration of the circuit blocks may be seen on a functional level in Figure 2.1 .
Refer to the circuit diagrams in Section 6.2 for more detail.

Exciter

Reference

Oscillator

12.8MHz

Microphone

Line

Transformer

Synthesiser

Audio

Processor

+22dBm

Lock
Detect

&

Gate

PIN

Switch

Time

Delay

Time

Delay

Power

Control

Drive
Amp.

Ramp

Gen.

Output

(+30dBm to

+33dBm)

PA

Time

Delay

Directional

Coupler

Low Pass

Filter

Transmitter
Output
(25W)

VCO

Tx Reg

Figure 2.1 T854 High Level Block Diagram

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C2.4 T854 Circuit Operation M800 SL2

2.2 Microcontroller

(Refer to the microcontroller circuit diagram (sheet 8) in Section 6.2 or 6.3.)

Watchdog

Reset

Microcontroller Cavity

Channel

Auxiliary

Output

EEPROM

Select

Port

Dual Digital

Potentiometer

Port

Synthesiser

12.8MHz
Clock

External

Serial

Port

CTCSS Tone

5V Digital
Regulator

5V Reset

Microcontroller

Converter

CTCSS

Encoder

Figure 2.2 T854 Microcontroller Block Diagram

Overall system control of the T854 is accomplished by the use of a member of the 80C51
family of microcontrollers (IC810). It runs from internal ROM and RAM, thus leaving
all four ports free for input/output functions.

Non-volatile data storage is achieved by serial communication with a 16kBit EEPROM
(IC820). This serial bus is also used by the microcontroller to program the synthesiser
(IC740) and deviation control EPOTS (IC220).

The main tasks of the microcontroller are as follows:

• program the synthesiser and EPOT;

• interface with the PGM800Win programming software at 9600 baud via the

serial communication lines on D-range 1 (PL100) & D-range 2;

• monitor channel change inputs from D-range 2;

• generate timing waveforms for CTCSS encoding;

• coordinate and implement timing control of the exciter/transmitter.

• control the front panel "Supply" LED (refer to Section 5.3).

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M800 SL2 T854 Circuit Operation C2.5

m

2.3 Synthesised Local Oscillator

(Refer to the synthesiser circuit diagram (sheet 7) in Section 6.2 or 6.3 and the VCO cir­cuit diagram in Part E.)

12.8MHz

Reference

Oscillator

Ref

Mod

Serial

Bus

Clk
Data
En

Fixed

Divider

/64

Phase

Modulator

FREQUENCY SYNTHESISER IC

Reference

f

ref

Controller

Divider

/R

Phase

Detector

Programmable

Divider

/N

Charge

Pump

Loop
Filter

Prescaler

64/65

Modulation

f

in

VCO

Σ

VCO Buffer

Divider Buffer

VCO PCB

Output

Buffer

Figure 2.3 T854 Synthesiser Block Diagram

The synthesiser (IC740) employs a phase-locked loop (PLL) to lock a voltage controlled
oscillator (VCO) to a given reference frequency. The synthesiser receives the divider
information from the control microprocessor via a 3 wire serial bus (clock, data, enable).
When the data has been latched in, the synthesiser processes the incoming signals from
the VCO buffer (f

) and the phase modulator (f

in

ref

).

A reference oscillator at 12.8MHz (=IC700) is buffered (IC710 pins 3 & 4) and divided
down to 200kHz (IC730). This 200kHz square wave is then summed with the modulat­ing audio and passed to an integrator (IC720 pins 9 & 8, Q710, Q720). This produces a
ramping waveform which is centred around a DC level determined by the incoming
audio. IC720 pins 5 & 6 perform as a comparator, ultimately producing a phase-modu­lated 200kHz square wave. This is followed by another phase shifting stage (IC720 pins
3 & 4, Q730, Q740), before being divided down to 6.25kHz or 5kHz within the synthe­siser IC (IC740).

+22dB

L.O.

A buffered output of the VCO (Q795) is divided with a prescaler and programmable
divider which is incorporated into the synthesiser chip (IC740). This signal is compared
with the phase modulated reference signal at the phase detector (also part of the synthe­siser chip). The phase detector outputs drive a balanced charge pump circuit (Q760,
Q770, Q775, Q780, Q785) and active loop filter (IC750 pins 5, 6 & 7, Q790) which pro­duces a DC voltage between 0V and 20V to tune the VCO. This VCO control line is fur­ther filtered to attenuate noise and other spurious signals. Note that the VCO frequency
increases with increasing control voltage.

If the synthesiser loop loses lock, a pulsed signal appears at LD (pin 2) of IC740. This
signal is filtered and buffered by IC750 pins 1, 2 & 3, producing the Lock-Detect signal
used to shut off the power supply to the drive amplifier. IC750 pin 1 is at 20V when the
synthesiser is out of lock.

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C2.6 T854 Circuit Operation M800 SL2

2.3.1 Two Point Modulation

Frequency modulation occurs by modulating both the VCO input and the synthesiser
reference input. This process is called two point modulation and ensures a flat modula­tion response from 67Hz to 3kHz (2.55kHz for narrow bandwidth).

The PLL has a fast response time, allowing a Tx key-up time of <30ms. Because of this
fast response time the PLL sees lower modulation frequencies superimposed on the
VCO as an error and corrects for it, resulting in no modulation on the carrier. At modu­lation frequencies greater than 300Hz the loop cannot correct fast enough and modula­tion is seen on the carrier. The response of the loop to VCO modulation is shown by f
in Figure 2.4 below.

To achieve low frequency modulation, the reference oscillator is also modulated so that
the phase detector of IC740 detects no frequency error under modulation. Thus, the
synthesiser loop will not attempt to correct for modulation and the audio frequency
response of the transmitter remains unaffected. The response of the loop to reference
frequency modulation is shown by f

The reference modulation is controlled by a 256-step 10k electronic potentiometer
(EPOT) which is adjustable via PGM800Win. The EPOT is made up of 256 resistive sec­tions (representing approximately 39Ω each) which can be individually addressed by
the microcontroller. Each section can be switched in or out of circuit to achieve the
required total resistance, thus giving control of the reference modulation.

in Figure 2.4.

1

2

Deviation

ff

12

TCXO VCO

Frequency

Figure 2.4 T854 Two Point Modulation

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