Daniels VT-3/140-SWA2, Instruction Manual

Page: 10 / 262

VHF Enhanced Transmitter Instruction Manual VT-3 132 - 174 MHz 2-1
2 SYSTEM OVERVIEW
2.1 Transmitter Operation
Several modules are integrated by the VT-3 Transmitter Main board to provide the complete
transmitter. The Transmitter Main Board, Front Panel Board and Audio Processor are generic in
that they apply to all transmitter models. The Front Panel Board and Audio Processor are soldered
directly to the Transmitter Main Board and are treated collectively in the Transmitter Main Board
Manual. The operating frequency and power range is determined by the choice of Amplifier and
Frequency Synthesizer Module, which plugs in to the Transmitter Main Board and can be changed
with minimal effort. Circuitry and jumpers on the Transmitter Main Board control the operation of
all modules and the operation of the transmitter, overall. Technical details and a complete
description of transmitter operation can be found in the Transmitter Main Board Manual.
The VT-3 132 - 174 MHz transmitter requires two power supplies; a regulated +9.5 Vdc supply
and a +13.8 Vdc supply, the latter of which is connected only to the Amplifier Module. The
(nominally) +13.8 Vdc supply's range is +11 Vdc to +16 Vdc. For the 0.5 to 2.0 Watt
transmitters, there is no current drawn on the 13.8 Vdc supply. For the 2.0 to 8.0 Watt transmitters,
the current drawn from the +13.8 Vdc supply (while transmitting at the rated power) is
approximately
1000 mA with temperature, operating frequency and power supply voltage. The
current drawn by the 13.8 Vdc line should not exceed 1500 mA . The +9.5 Vdc current drawn by
all transmitter models while transmitting at the rated power is approximately 1300 mA and should
not exceed 1500 mA. The VT-3 Transmitter has four different standby modes that trade-off
standby current consumption for start-up speed. The standby modes are determined by three
jumpers (refer to the MT-3 Transmitter Main Board Manual): jumper J6 which always turns on the
'+9.5 Vdc Switched' supply, jumper J7 which selects the power source for the MT-3 Audio
Processor and jumper J18 which selects the enable line for the OS-3H150 Synthesizer Module.
• MODE 1: Jumper J6 out
- the audio processor is switched by a PTT signal
- the synthesizer module is switched by a PTT signal
- standby current:
Typically 7 mA
- start-up time: Typically 50 ms