User Manual
Table Of Contents
- 1GENERAL
- 1.1Introduction
- 1.2Manual Organization
- 1.3VT-4B 136 - 174 MHz Transmitter Family Models
- 1.4Performance Specifications
- 1.4.1General
- 1.4.2Audio Specifications
- 1.4.3Physical Specifications
- 2THEORY OF OPERATION
- 2.1Transmitter Operation
- 2.2Transmitter Programming
- 2.2.1Transmitter Wide Options
- 2.2.1.1Disable Front Panel Led
- 2.2.1.2Secure Hardware Equipped
- 2.2.1.3Allow Emergency Transmissions
- 2.2.1.4Allow Radio Inhibit
- 2.2.1.5Allow Radio Check
- 2.2.1.6Enable Status
- 2.2.1.7Frequency Band
- 2.2.2Channel Wide Settings
- 2.2.2.1Frequency
- 2.2.2.2Voice/Signal Type
- 2.2.2.3Squelch Type
- 2.2.2.4CTCSS Tone
- 2.2.2.5Enable Reverse Burst
- 2.2.2.6DCS Code
- 2.2.2.7DCS Invert
- 2.2.2.8Enable Turn Off Code
- 2.2.2.9Transmitter Power
- 2.2.2.10Channel Bandwidth
- 2.2.2.11Deviation
- 2.2.2.12Time Out Timer
- 2.2.2.13Channel Status
- 2.2.2.14Transmitter Pre-emphasis
- 2.2.2.15NAC Transmitter Code
- 2.2.2.16NAC Transmitter
- 2.3Transmitter Programming using Motorola Radio Service Software
- 2.4Secure Communications
- 2.5Transmitter Assembly and Adjustment
- 2.5.1Controller Board Alignment
- 2.5.1.1Reference Oscillator Adjustment
- 2.5.1.2Transmitter Deviation Balance Adjustment
- 2.5.1.3Transmitter Deviation Limit Adjustment
- 2.5.2Amplifier Alignment
- 2.5.3Frequency Change
- 2.6Recommended Test Equipment List
- 2.7Repair Note
- 2.8Printed Circuitboard Numbering Convention
- 3ILLUSTRATIONS
- 3.1MT-4 Base Transmitter Front Panel
- 3.2MT-4 Transmitter Case - Exploded View
- 3.3Digital Base Transmitter Block Diagram
- 3.4Digital Base Transmitter Schematic Diagram
- 3.5Digital Base Transmitter Main Board Component Layout (Bottom)
- 3.6Digital Base Transmitter Main Board Component Layout (Top)
- 4PARTS LIST
- 4.1P25 Base Transmitter Main Board Parts List
- 4.1.1P25 Base Transmitter Main Board Electrical Parts List
- 4.1.2P25 Base Transmitter Mechanical Parts List
- 5REVISION HISTORY
DE
DANIELS
ELECTRONICS
VT-4B150 VHF Project 25
Digital
Base
Transmitter
Instruction
Manual
2-3
2.2.2
Channel Wide Settings
There are currently 32 channels, which may be individually programmed for various parameters.
2.2.2.1 Frequency
The transmitter’s frequency may be set here. The Radio Programming Software will only allow
frequencies within the operation band (set in the Transmitter Wide options above) to be entered.
2.2.2.2
Voice/Signal Type
Allowed values are PROJECT 25, ANALOG and MIXED MODE. PROJECT 25 mode receives
digital P25 modulated signals only, while ANALOG mode receives analog FM signals only. In
MIXED MODE the transmitter will transmit either PROJECT 25 digital and analog signals,
depending on which mode of signal was received. When either ANALOG or MIXED MODE
values are selected, additional combo boxes appear to allow selection of Squelch Type for
ANALOG mode signals.
2.2.2.3
Squelch Type
This option is available for ANALOG signals only, and may be set to CSQ, CTCSS or DCS.
With the CSQ option, the transmitter will not send either a CTCSS subaudible tone or a DCS code
along with the signal being transmitted. With the CTCSS option the transmitter will send a
subaudible Continuous Tone Coded Squelch System tone along with the audio signal. Similarly,
when the DCS option is used the transmitter will transmit a Digital Controlled Squelch code with
the audio signal. When either CTCSS or DCS Squelch Type is selected, additional combo boxes
appear to allow selection of a particular tone or code.
2.2.2.4
CTCSS Tone
The frequency of the CTCSS tone may be selected here. All the thirty-nine standard frequencies
are supported, along with three non-standard frequencies.
2.2.2.5 Enable Reverse Burst
This option enables a Reverse CTCSS Burst to be sent at the end of a transmission. The Reverse
Burst signals to the receiving radio that the transmission is ending, allowing it to mute more
quickly.
2.2.2.6
DCS Code
One of eighty-six DCS codes may be selected here.