Motorola Pro Series Elite User manual

i
DOCUMENT HISTORY
The following major changes have been implemented in this manual since the previous edition:
Edition Description Date
6881094C21-O Initial edition Dec. 2001
6881094C21-B Added changes from FMR2027-1 into manual.
Added Full keypad (FKP) controller board, sche-
matics and parts lists (PCB no.8471678L01).
Added Limited keypad (LKP) controller board, sche-
matics and parts lists (PCB no.8471679L01).
Added VHF Main Board, Controls and Switches,
Receiver, Synthesizer, VCO andTransmitter Dia-
grams, Parts List (PCB no. 8471021L01)
Added UHF Band 1 Main Board, Controls and
Switches, Receiver, Synthesizer, VCO and Trans-
mitter Diagrams, Parts List (PCB no. 8471441L01).
Added UHF Band 2 Main Board, Controls and
Switches, Receiver, Synthesizer, VCO and Trans-
mitter Diagrams, Parts List (PCB no. 8471475L01).
Added new universal controller flexes (PCB no.
8471612L01 and 8471698L01).
Updated model charts for UHF Band 1, UHF Band 2
and VHF to incIude IP67 radios.
Jan. 2007

ii
Notes

Safety-iii
PRODUCT SAFETY AND RF EXPOSURE COMPLIANCE
ATTENTION!
This radio is restricted to occupational use only to satisfy FCC RF energy exposure
requirements. Before using this product, read the RF energy awareness information and operating
instructions in the Product Safety and RF Exposure booklet enclosed with your radio (Motorola
Publication part number 68P81095C98) to ensure compliance with RF energy exposure limits.
For a list of Motorola-approved antennas, batteries, and other accessories, visit the following web site
which lists approved accessories: http://www.motorola.com/cgiss/index.shtml.
Before using this product, read the operating instructions for safe usage contained in the
Product Safety and RF Exposure booklet enclosed with your radio.
!
C a u t i o n

Safety-iv
Notes

v
Table of Contents
Product Safety and RF Exposure Compliance...........................................iii
Chapter 1 Introduction.............................................................................. 1-1
1.1 Scope of Manual............................................................................................................................ 1-1
1.2 Warranty and Service Support....................................................................................................... 1-1
1.2.1 Warranty Period................................................................................................................ 1-1
1.2.2 Return Instructions............................................................................................................ 1-1
1.2.3 After Warranty Period ....................................................................................................... 1-1
1.3 Related Documents ....................................................................................................................... 1-2
1.4 Technical Support.......................................................................................................................... 1-2
1.4.1 Piece Parts Availability ..................................................................................................... 1-2
1.5 Radio Model Chart and Specifications........................................................................................... 1-3
1.6 Radio Model Information................................................................................................................ 1-3
Chapter 2 Theory of Operation ................................................................ 2-1
2.1 Introduction .................................................................................................................................... 2-1
2.2 Radio Power Distribution ............................................................................................................... 2-1
2.3 Keypad........................................................................................................................................... 2-2
2.4.2 Real Time Clock (RTC)..................................................................................................... 2-4
2.4.3 Circuit Description............................................................................................................. 2-4
2.4.4 ModB/Vstby Supply ..........................................................................................................2-5
2.5 VHF Transmitter ............................................................................................................................ 2-5
2.5.2 Antenna Switch................................................................................................................. 2-6
2.5.3 Harmonic Filter ................................................................................................................. 2-6
2.5.4 Antenna Matching Network............................................................................................... 2-6
2.5.5 Power Control Integrated Circuit (PCIC)........................................................................... 2-6
2.5.6 VHF Receiver ................................................................................................................... 2-7
2.5.7 Receiver Front-End........................................................................................................... 2-7
2.5.8 Receiver Back-End ........................................................................................................... 2-8
2.5.9 Automatic Gain Control Circuit ......................................................................................... 2-8
2.5.10 Frequency Generation Circuitry........................................................................................ 2-9
2.5.11 Synthesizer ..................................................................................................................... 2-10
2.5.12 Voltage Controlled Oscillator (VCO) ............................................................................... 2-11
2.6 UHF Transmitter (Band 1 and Band 2) ........................................................................................ 2-12
2.6.1 Power Amplifier............................................................................................................... 2-13
2.6.2 Antenna Switch............................................................................................................... 2-13
2.6.3 Harmonic Filter ............................................................................................................... 2-13
2.6.4 Antenna Matching Network............................................................................................. 2-13
2.6.5 Power Control Integrated Circuit (PCIC)......................................................................... 2-13
2.6.6 UHF Receiver (Band 1 and Band 2) ............................................................................... 2-14
2.6.7 Receiver Front-End.........................................................................................................2-14
2.6.8 Receiver Back-End ......................................................................................................... 2-15
2.6.9 Automatic Gain Control Circuit ....................................................................................... 2-15
2.6.10 Frequency Generation Circuitry...................................................................................... 2-16
2.6.11 Synthesizer ..................................................................................................................... 2-16
2.6.12 Voltage Controlled Oscillator - (VCO) ............................................................................. 2-18

vi
Chapter 3 Maintenance ............................................................................. 3-1
3.1 Introduction .................................................................................................................................... 3-1
3.2 Preventive Maintenance ................................................................................................................ 3-1
3.2.1 Inspection.......................................................................................................................... 3-1
3.2.2 Cleaning............................................................................................................................ 3-1
3.3 Safe Handling of CMOS and LDMOS............................................................................................ 3-2
3.4 General Repair Procedures and Techniques................................................................................. 3-2
3.5 Shields ........................................................................................................................................... 3-3
3.6 Recommended Test Tools............................................................................................................. 3-4
3.7 Replacing the Circuit Board Fuse. ................................................................................................. 3-6
3.8 Removing and Reinstalling the Circuit Board ................................................................................ 3-8
3.9 Error Codes.................................................................................................................................... 3-8
3.10 VHF Troubleshooting Charts ....................................................................................................... 3-10
Troubleshooting Flow Chart for Controller ...................................................................................... 3-10
Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)................................................................. 3-11
Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)................................................................. 3-12
Troubleshooting Flow Chart for Transmitter.................................................................................... 3-13
Troubleshooting Flow Chart for Synthesizer ................................................................................... 3-14
Troubleshooting Flow Chart for VCO ..............................................................................................3-15
3.11 UHF (Band 1 and Band 2) Troubleshooting Charts ..................................................................... 3-16
Troubleshooting Flow Chart for Controller ...................................................................................... 3-16
Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)................................................................. 3-17
Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)................................................................. 3-18
Troubleshooting Flow Chart for Transmitter.................................................................................... 3-19
Troubleshooting Flow Chart for Synthesizer ................................................................................... 3-20
Troubleshooting Flow Chart for VCO ..............................................................................................3-21
3.12 Keypad Troubleshooting Chart .................................................................................................... 3-22
Chapter 4 Schematic Diagrams, Overlays, and Part Lists .................... 4-1
4.1 Introduction .................................................................................................................................... 4-1
4.1.1 Notes For All Schematics and Circuit Boards ................................................................... 4-1
4.2 RF - Controller Interconnect Flex................................................................................................... 4-2
4.2.1 Plain .................................................................................................................................. 4-2
4.2.2 Keypad.............................................................................................................................. 4-2
4.2.3 Schematic for RF - Controller Interconnect Flex............................................................... 4-3
4.2.4 Parts List for Keypad-Controller Interconnect Flex ........................................................... 4-3
4.2.5 Universal Connector Flex Plain......................................................................................... 4-4
4.2.6 Universal Connector Flex Keypad .................................................................................... 4-6
4.2.7 Schematic for Universal Connector Flex Plain.................................................................. 4-8
4.2.8 Parts List for Universal Connector Flex Plain ................................................................... 4-8
4.2.9 Parts List for Universal Connector Flex Plain (For Flex No. 8471612L01) ....................... 4-8
4.2.10 Schematic for Universal Connector Flex Keypad ............................................................. 4-9
4.2.11 Parts List for Universal Connector Flex Keypad ............................................................... 4-9
4.2.12 Parts List for Universal Connector Flex Keypad (For Flex 8471698L01).......................... 4-9
5.1 Controller Board Diagrams ............................................................................................................ 5-1
6.1 VHF Circuit Board/ Schematic Diagrams and Parts List ................................................................ 6-1
VHF Radio Parts List......................................................................................................................... 6-9
6.2 VHF Circuit Board/ Schematic Diagrams and Parts List (PCB No. 8471021L01) ....................... 6-13
Parts List for VHF (for PCB No. 8471021L01) ................................................................................ 6-22
7.1 UHF Band 1, Circuit Board/Schematic Diagrams and Parts List ................................................... 7-1

vii
UHF Band 1 Radio Parts List ............................................................................................................ 7-9
7.2 UHF Band 1, Circuit Board/ Schematic Diagrams and Parts List (PCB No. 8471441L01).......... 7-11
UHF Band 1 Radio Parts List (PCB No. 8471441L01) ................................................................... 7-20
8.1 UHF Band 2, Circuit Board/Schematic Diagrams and Parts List ................................................... 8-1
UHF Band 2 Radio Parts List ............................................................................................................ 8-9
8.2 UHF Band 2, Circuit Board/Schematic Diagrams and Parts List (PCB No.8471475L01)............ 8-11
UHF Band 2 Radio Parts List (PCB No. 8471475L01) ................................................................... 8-20

viii
Notes

1-1
Chapter 1 Introduction
1.1 Scope of Manual
This manual is intended for use by service technicians familiar with similar types of equipment. It
contains service information required for the equipment described and is current as of the printing
date. Changes that occur after the printing date are incorporated by a complete manual revision or
alternatively, as additions.
1.2 Warranty and Service Support
Motorola offers long term support for its products. This support includes full exchange and/or repair of
the product during the warranty period, and service/repair or spare parts support out of warranty. Any
“return for exchange” or “return for repair” by an authorized Motorola dealer must be accompanied by
a warranty claim form. Warranty claim forms are obtained by contacting customer service.
1.2.1 Warranty Period
The terms and conditions of warranty are defined fully in the Motorola dealer or distributor or reseller
contract. These conditions may change from time to time and the following notes are for guidance
purposes only.
1.2.2 Return Instructions
In instances where the product is covered under a “return for replacement” or “return for repair”
warranty, a check of the product should be performed prior to shipping the unit back to Motorola. This
is to ensure that the product has been correctly programmed or has not been subjected to damage
outside the terms of the warranty.
Prior to shipping any radio back to a Motorola warranty depot, please contact the appropriate
customer service for instructions. All returns must be accompanied by a warranty claim form,
available from your customer services representative. Products should be shipped back in the original
packaging, or correctly packaged to ensure no damage occurs in transit.
1.2.3 After Warranty Period
After the Warranty period, Motorola continues to support its products in two ways:
Firstly, Motorola's Accessories and Aftermarket Division (ADD) supplies individual parts and modules
that can be purchased by dealers who are technically capable of performing fault analysis and repair.
Secondly, Motorola’s service department offers a repair service to both end users and dealers at
competitive prices.
NOTE Before operating or testing these units, please read the Safety Information Section in
the front of this manual.

1-2 Related Documents
1.3 Related Documents
The following documents are directly related to the use and maintainability of this product.
1.4 Technical Support
Technical support is available to assist the dealer/distributor and self-maintained customers in
resolving any malfunction which may be encountered. Initial contact should be by telephone to
customer resources wherever possible. When contacting Motorola technical support, be prepared to
provide the product model number and the unit’s serial number. The contact locations and telephone
numbers are located in the Basic Service Manual listed under the Related Documents paragraph of
this chapter.
1.4.1 Piece Parts Availability
Some replacement parts, spare parts, and/or product information can be ordered directly. If a
complete Motorola part number is assigned to the part, and it is not identified as “Depot ONLY”, the
part is available from Motorola Accessories and Aftermarket Division (AAD). If no part number is
assigned, the part is not normally available from Motorola. If the part number is appended with an
asterisk, the part is serviceable by a Motorola depot only. If a parts list is not included, this generally
means that no user-serviceable parts are available for that kit or assembly.
Title Part Number
Service Manual, Basic, Engl, NA
Service Manual, Basic, Engl, LA
Service Manual, Basic, Span
Service Manual, Basic, Port
Service Manual, Detailed, Engl
Service Manual, Detailed, Span
Service Manual, Detailed, Port
68P81094C00
68P81094C01
68P81094C02
68P81094C03
68P81094C21
68P81094C22
68P81094C23
Parts Order Entry
7:00 A. M. to 7:00 P. M. (Central Standard
Time)
Monday through Friday (Chicago, U. S. A.)
To Order Parts in the United States of
America:
1-800-422-4210, or 847-538-8023
1-800-826-1913, or 410-712-6200 (U. S.
Federal Government)
TELEX: 280127
FAX: [phone]
FAX: [phone] (U. S. Federal Gov-
ernment)
(U. S. A.) after hours or weekends:
1-800-925-4357
To Order Parts in Latin America and the
Caribbean:
Please send an email to:
[e-mail]
Accessories and Aftermarket Division
(United States and Canada)
Attention: Order Processing
1313 E. Algonquin Road
Schaumburg, IL 60196
Accessories and Aftermarket Division
Attention: Latin America and Caribbean
Order Processing
1313 E. Algonquin Road
Schaumburg, IL 60196
Parts Identification
1-847-538-0021 (Voice)
1-847-538-8194 (FAX)

Radio Model Chart and Specifications 1-3
1.5 Radio Model Chart and Specifications
The radio model charts and specifications are located in the Basic Service Manual listed under the
Related Documents paragraph of this chapter.
1.6 Radio Model Information
The model number and serial number are located on a label attached to the back of your radio. You
can determine the RF output power, frequency band, protocols, and physical packages from these
numbers. The example below shows one portable radio model number and its specific
characteristics.
Table 1-1. Radio Model Number
Example: LAH38KDC9AA3
Type of
Unit
Model
Series
Freq.
Band
Power
Level
Physical
Packages
Channel
Spacing Protocol Feature Level
Model
Revision
Model
Package
AA
or
LA
H38 K
VHF
(136-
174MHz)
D
4-5W
C9
Program-
mable
AA
Conven-
tional
3A N
R
UHF1
(403-
470MHz)
DU
LTR
6
S
UHF2
(450-
527MHz)
LA = Motorola Internal Use
H= Portable

1-4 Radio Model Information
Notes

2-1
Chapter 2 Theory of Operation
2.1 Introduction
This section provides a detailed theory of operation for the radio and its components.
2.2 Radio Power Distribution
Figure 2-1. DC Power Distribution Block Diagram
A Block diagram of the DC power distribution throughout the radio board is shown in Figure 2-1. A
7.5V battery (BATT 7.5V) supplies power directly to the electronic ON/OFF control as UNSWB+.
When the radio is turned on, MECH_SWB+ (ON/OFF volume control) will trigger the electronic ON/
OFF control (momentary-on path), then SWB+ is distributed. Vdda from 3.3V Vdda regulator will then
supply the microprocessor. Data is then sent to ASFIC_CMP to turn on GCB4(DAC). GCB4 will take
over the momentary-on path within 12ms. SWB+ will continue to support the whole board until the
radio is turned off.
Radio will be turned-off on two conditions;
1. MECH_SWB+ turned off
2. Low battery
When low battery level is detected by the microprocessor through both conditions above, it will store
the radio personality data to EEPROM before turning off.
SWB+
Fuse
Low Battery
Detect
Antenna
PCIC(ALC)
PA, Driver
LI Ion
3.5V
Reg.
Audio
ASFIC_CMP VCOBIC
FRACTN LVZIF
LCD
Driver
5V
RF. AMP, IF AMP
Ext. RX.
MECH.
SWB+
UNSWB+
TX.
R1
R5
R2
R3
Vdda
Vddd
MCU, MicroP, ROM
and EEPROM
Buffer (NU)
Led
Control
7.5V
Battery
Vdda
Regulator
Vddd
Regulator
5V
Regulator
Switch
On/Off Switch
Power
Amplifier

2-2 Keypad
2.3 Keypad
The keypad block diagram is shown in Figure 2-2. The LED_EN setting is set by the codeplug. When
the value is set to high, the LED will not light up during power up and vice versa.
U602 is a comparator that will compare the voltage when any one of the keypad row or keypad
column keys is being pressed. Therefore when a key is being pressed, it will send a message to the
microprocessor through the output (KEY_INT) telling it that a key has been pressed. The
microprocessor will then sample the Analog to Digital voltages at the keypad row and keypad column
and map it with the table so that the key being pressed can be identified. Once the key has been
identified, the message that corresponds to the key will show up at the display.
Figure 2-2. Keypad Block Diagram
Table 2-1. Vdd Regulator Band and Radio Jumpers
Jumpers Dual Vdd Regulator
Scheme
Single Vdd Regulator
Scheme
R1 Y Y
R2 N N
R3 N Y
R4 N N
R5 Y N
Vdda Y N
SW. Reg. N N
Micro Processor
Comparator
Keypad
Button
LED
Display
18 pin connector
Key_Int
Keypad Column
Keypad
Data
Row

Keypad 2-3
2.4 Controller Board
The controller board is the central interface between the various subsytems of the radio. It is
separated into digital and audio architectures. The digital portion consists of a special Motorola
microcontroller (HC11FL0). The audio power amplifier (Audio PA) and audio/signalling/filter/
companding IC (ASFIC_CMP) form the backbone of the audio/signalling architecture.
Figure 2-3. Controller Block Diagram
External
Microphone
Internal
Microphone
External
Speaker
Internal
Speaker
SCI to Side
Connector
Audio
PA
Audio/Signalling
Architecture
To Synthesizer
Mod
Out
16.8 MHz
Reference Clock
from Synthesizer
Recovered Audio
Squelch
To RF Board SPI
Digital
Architecture
µP Clock
3.3V
Regulator
(Vddd)
RAM
EEPROM
ROM
HC11FL0
ASFIC_CMP
3.3V
Regulator
(Vdda)

2-4 Keypad
2.4.1 MCU Configuration
There is one common MCU architecture for low-tier as well as for the high-tier products. It covers the
Conventional and Trunking portables. An open architecture system with the new HC11FL0 as the
processor is used. Combinations of different size RAM, ROM and EEPROM are available for various
application software.
2.4.2 Real Time Clock (RTC)
This radio supports Real Time Clock (RTC) module for purposes of Message Time Stamping and
Time Keeping. The RTC module resides in the micro-processor HC11FL0. It is kept alive by a back-up
Lithium Ion battery when the primary battery is removed.
2.4.3 Circuit Description
The RTC module circuit, shown in Figure 2-4, which resides in the HC11FL0 is powered by the ModB/
Vstby pin and PI6/PI7 form the crystal oscillator circuit. Clock frequency of 38.4kHz from a crystal
oscillator provides the reference signal. In the processor, the frequency is divided down to 1Hz.
As the RTC module is powered separately from the processor Vdd, the RTC is kept alive through the
ModB / Vstby pin when the radio is switched off. A small button Lithium Ion battery continues to feed
the RTC when the primary battery is removed.
A MOSFET Q416 switches in the Li (Lithium) Ion supply when Vdd is removed. Q416 also provides
isolation from BOOT_CTRL function in the event of radio program flashing. A small 3.3V regulator is
used to charge the Li (Lithium) Ion battery.
Figure 2-4. RTC Circuit
LI_ION
R462
R419
3
4
2
15
CR411
1
2
3
Q416
C
U410 3.3V
3
2
1
VIN VOUT
VSS
UNSWB+
R460
C435
R461
Vddd
HC11FL0
MODA
MODB
R420
R426
FL401 C436
C437
PI6
PI7
OUT
IN
GND
38.4kHz
UNSWB+ SWB+
6
4
1
3
2
3
51
2
4
CR413
R463
300
Q417
TEST_POINT
TP405
1
BOOT_CTRL

VHF Transmitter 2-5
2.4.4 ModB/Vstby Supply
The supply to the ModB/Vstby pin varies depending on the conditions listed in Table 2-2
2.5 VHF Transmitter
The VHF transmitter, shown in Figure 2-5, contains five basic circuits:
• Power Amplifier
• Antenna Switch
• Harmonic Filter
• Antenna Matching Network
• Power Control Integrated Circuit (PCIC).
Table 2-2. ModB/Vstby Supply Modes
Condition Circuit Operation
Radio On Vdd supply voltage via CR411
Radio Off • Vdd turned off
• Q416 gate is pulled low by R462
• Q416 is switched on
• U410 supplies 3.2V to ModB/Vstby
Primary battery removed • Vdd turned off
• Q416 gate is pulled low by R462
• Q416 is switched on
• Li Ion battery provides 3.2V to ModB/Vstby
Flash Mode • Boot_Ctrl line pull low
• ModA & ModB goes low
• Processor in boot-strap mode
• Flashing enabled
Figure 2-5. Transmitter Block Diagram
PCIC
Antenna
PA
Driver
Vcontrol Vcontrol
From VCO
Jack
Antenna Switch/
Harmonic Filter/
Matching Network
PA-Final
Stage

2-6 VHF Transmitter
2.5.1 Power Amplifier
The power amplifier consists of two devices:
• 9Z67 LDMOS driver IC (U3501) and
• PRF1507 LDMOS PA (Q3501).
The 9Z67 LDMOS driver IC contains a 2 stage amplification with a supply voltage of 7.3V.
This RF power amplifier is capable of supplying an output power of 0.3W (pin 6 and 7) with an input
signal of 2mW (3dBm) (pin16). The current drain would typically be 130mA while operating in the
frequency range of 136-174MHz.
The PRF1507 LDMOS PA is capable of supplying an output power of 7W with an input signal of 0.3W.
The current drain would typically be 1800mA while operating in the frequency range of 136-174MHz.
The power output can be varied by changing the biasing voltage.
2.5.2 Antenna Switch
The antenna switch circuit consists of two PIN diodes (D3521 and D3551), a pi network (C3531,
L3551 and C3550), and three current limiting resistors (R3571, R3572, R3573). In the transmit mode,
B+ at PCIC (U3502) pin 23 will go low and turn on Q3561 where a B+ bias is applied to the antenna
switch circuit to bias the diodes “on”. The shunt diode (D3551) shorts out the receiver port, and the pi
network, which operates as a quarter wave transmission line, transforms the low impedance of the
shunt diode to a high impedance at the input of the harmonic filter. In the receive mode, the diodes
are both off, and hence, there exists a low attenuation path between the antenna and receiver ports.
2.5.3 Harmonic Filter
The harmonic filter consists of C3532 to C3536, L3531 and L3532. This network forms a low-pass
filter to attenuate harmonic energy of the transmitter to specifications level. The harmonic filter
insertion loss should be less than 1.2dB.
2.5.4 Antenna Matching Network
A matching network which is made up of L3538 and C3537 is used to match the antenna's
impedance to the harmonic filter. This will optimize the performance of the transmitter and receiver
into an antenna.
2.5.5 Power Control Integrated Circuit (PCIC)
The transmitter uses the Power Control IC (PCIC), U3502 to control the power output of the radio by
maintaining the radio current drain. The current to the final stage of the power module is supplied
through R3519 (0.1ohms), which provides a voltage proportional to the current drain. This voltage is
then fedback to the Automatic Level Control (ALC) within the PCIC to keep the whole loop stable.
The PCIC has internal digital to analog converters (DACs) which provide the reference voltage of the
control loop. The voltage level is controlled by the microprocessor through the data line of the PCIC.
There are resistors and integrators within the PCIC, and external capacitors (C3562, C3563 and
C3565) in controlling the transmitter rising and falling time. These are necessary in reducing the
power splatter into adjacent channels.
U3503 and its associated circuitry acts as a temperature cut back circuitry. This circuitry provides the
necessary voltage to the PCIC to cut the transmitter power when the radio temperature gets too high.

VHF Transmitter 2-7
2.5.6 VHF Receiver
The VHF receiver consists of a front end, back end, and automatic gain control circuits. A block
diagram of the VHF receiver is shown in Figure 2-6. Detailed descriptions of these features are
contained in the paragraphs that follow.
2.5.7 Receiver Front-End
The RF signal is received by the antenna and applied to a low-pass filter. For VHF, the filter consists
of L3531, L3532, C3532 to C3563. The filtered RF signal is passed through the antenna switch. The
antenna switch circuit consists of two PIN diodes (D3521 and D3551) and a pi network (C3531,
L3551 and C3550). The signal is then applied to a varactor tuned bandpass filter. The VHF bandpass
filter comprises of L3301, L3303, C3301 to C3304 and D3301. The bandpass filter is tuned by
applying a control voltage to the varactor diode (D3301) in the filter.
The bandpass filter is electronically tuned by the DACRx from IC404 which is controlled by the
microprocessor. Depending on the carrier frequency, the DACRx will supply the tuned voltage to the
varactor diodes in the filter. Wideband operation of the filter is achieved by shifting the bandpass filter
across the band.
The output of the bandpass filter is coupled to the RF amplifier transistor Q3302 via C3306. After
being amplified by the RF amplifier, the RF signal is further filtered by a second varactor tuned
bandpass filter, consisting of L3305, L3306, C3311 to C3314 and D3302.
Both the pre and post-RF amplifier varactor tuned filters have similar responses. The 3 dB bandwidth
of the filter is about 12 MHz. This enables the filters to be electronically controlled by using a single
control voltage which is DACRx.
Figure 2-6. VHF Receiver Block Diagram
Demodulator
Synthesizer
Crystal
Filter
Mixer
Varactor
Tuned Filter
RF Amp
Varactor
Tuned Filter
Pin Diode
Antenna
Switch
RF Jack
Antenna
AGC
Control Voltage
from ASFIC
First LO
from FGU
Recovered Audio
Squelch
RSSI
IF IC
SPI Bus
16.8 MHz
Reference Clock
Second
LO VCO
IF Amp
U3220