DE
DANIELS
ELECTRONICS
VT-4B150 VHF Project 25 Digital Base Transmitter Instruction Manual
1-1
1
GENERAL
1.1
Introduction
The VT-4B P25 Digital Base Transmitter is capable of operating in 12.5 kHz / 15 kHz or 25 kHz /
30 kHz channels. The transmitter operates continuous duty in the 136 to 174 MHz frequency band
and its output power is continuously adjustable from 2.0 to 8.0 Watts. A modular design allows
each of the transmitter's modules: Transmitter Board, VT-3/150 Amplifier to be individually
assembled and tested. This facilitates construction, tuning, maintenance as well as troubleshooting
procedures. The module can support DES-OFB decryption with a plug in module.
The VT-4B Transmitter combines state of the art performance in a compact modular enclosure for
applications ranging from remote mountain top repeaters to congested urban radio environments.
Each receiver module is characterized by dependable, low maintenance performance under the
most severe environmental conditions.
The VT-4B Transmitter is compatible with all Daniel’s subrack and base station enclosures. It
supports a basic analog interface, and may be used in a mixed system with MT-2 and MT-3 series
receivers and transmitters. It is not intended for use as a component in a digital mode repeater
system.
1.2
Manual Organization
The organization of this manual reflects the modular makeup of the VT-4 product line. Each
module is fully described within its respective submanual, all of which are contained within this
document. In general, each submanual contains:
1. A functional description and specification summary,
2. A detailed technical description (Theory of Operation) and
3. Assembly, setup and alignment procedures relevant to that particular module.
The module manuals are as follows.
Note: material presented in a given "sub-manual" may include information related to other module
versions not directly applicable to the VT-4 136 - 174 MHz Transmitter.
VHF Amplifier Instruction Manual VT-3 132 - 174 MHz : The amplifier module provides the final
stages of RF power amplification and harmonic filtering for the transmitter. This manual is
intended primarily as a reference since the amplifier module is adjusted at the factory.
Radio Programming Software Instruction Manual : This manual provides instructions on using the
PC-based Radio Programming Software package to perform transmitter alignment and frequency
and mode selection.
1.3
VT-4B 136 - 174 MHz Transmitter Family Models
There are 2 distinct models in the VT-4B Transmitter family each with different bands of
operation. The 2 models are as follows:
• VT-4B140-00-000 - 136-150 MHz band, 2.0-8.0 Watt
• VT-4B160-00-000 - 150-174 MHz band, 2.0-8.0 Watt
The transmitters' band of operation is determined by select components in the amplifier.
