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UHF FM PMR446 Radio
VX-241PMR446
( VX-241-G3-1 )
Service Manual
Introduction
This manual provides technical information necessary for servicing the
VX-241PMR446 UHF FM PMR446 radio.
Servicing this equipment requires expertise in handling surface-mount chip com-
ponents. Attempts by non-qualified persons to service this equipment may result
in permanent damage not covered by the warranty, and may be illegal in some
countries.
Two PCB layout diagrams are provided for each double-sided circuit board in the
transceiver. Each side of is referred to by the type of the majority of components
installed on that side ("leaded" or "chip-only"). In most cases one side has only
chip components, and the other has either a mixture of both chip and leaded com-
ponents (trimmers, coils, electrolytic capacitors, ICs, etc.), or leaded components
only.
While we believe the technical information in this manual to be correct, VER-
TEX STANDARD assumes no liability for damage that may occur as a result of
typographical or other errors that may be present.
Your cooperation in pointing out any inconsistencies in the technical information
would be appreciated.
This transceiver is assembled using Pb (lead) free solder, based on the RoHS specification.
Only lead-free solder (Alloy Composition: Sn-3.0Ag-0.5Cu) should be used for repairs performed on this
apparatus. The solder stated above utilizes the alloy composition required for compliance with the lead-free
specification, and any solder with the above alloy composition may be used.
Specifications ........................................................................................................................ 2
Exploded View & Miscellaneous Parts .............................................................................. 3
Parts List ............................................................................................................................... 4
Block Diagram ...................................................................................................................... 5
Circuit Description .............................................................................................................. 6
Alignment.............................................................................................................................. 8
MAIN Uuit Circuit Diagram ............................................................................................. 14
MAIN Unit Parts Layout ................................................................................................... 15
VX-241PMR446 Service Manual
Important Note
Contents
Vertex Standard LMR, Inc.
©
2014 Vertex Standard LMR, Inc.
EC112U90C
1
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Table of Contents
Related Manuals for Vertex Standard VX-241-G3-1
Summarization of Contents
Specifications
General Specifications
General specifications including frequency range, power supply, dimensions, and weight.
Receiver Specifications
Receiver performance specifications, including audio output.
Transmitter Specifications
Transmitter performance specifications, including output power.
Circuit Description
Circuit Configuration by Frequency
Details the receiver's double-conversion super-heterodyne architecture.
Receiver System
Explains the RF amplifier, mixer, and IF stages of the receiver.
Squelch Circuit
Describes noise and carrier squelch operation and levels.
Transmitter System
Covers the microphone amplifier, VCO, and output power stages.
PLL Frequency Synthesizer
Describes the PLL IC, VCO, and TCXO for frequency control.
VCO
Explains the Voltage Controlled Oscillator's receive and transmit functions.
PLL
Details the Phase-Locked Loop operation and frequency locking.
Alignment Procedures
Required Test Equipment
Lists necessary equipment for performing alignment procedures.
Alignment Preparation & Precautions
Outlines steps and warnings before starting alignment.
Test Setup
Describes the initial setup for transceiver alignment procedures.
Basic Alignment Mode
Explains how to enter and utilize the software for alignment.
PLL Reference Frequency Alignment
Procedure to align the reference frequency for the PLL.
Squelch (SQL) / RSSI Alignment
Procedure for aligning Squelch and RSSI sensitivity levels.
Mic Sense Alignment
Procedure for adjusting microphone sensitivity (gain).
Maximum Deviation Alignment
Procedure for aligning the maximum frequency deviation.
Modulation Balance Alignment
Procedure for aligning modulation balance.
CTCSS Deviation Alignment
Procedure for aligning CTCSS deviation levels.
DCS Deviation Alignment
Procedure for aligning DCS deviation levels.
Battery Voltage Alignment
Procedure for aligning battery alert voltage and write protect level.
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