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SYSTEM OVERVIEW

2.1 Transmitter Operation

Several modules are integrated by the VT-3A130 Transmitter Main Board to provide the complete

transmitter. The Front Panel Board and AM Audio Processor are soldered directly to the

Transmitter Main Board and are treated collectively in the Transmitter Main Board Manual while

the Power Amplifier and and the Frequency Synthesizer plug into 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-3A130 transmitter requires two power supplies; a regulated + 9.5 Vdc supply and

+ 13.8 Vdc supply, the later of which is connected only to the Amplifier Module. The (nominally)

+13.8 Vdc supply's range is +10.0 Vdc to +17.0 Vdc. The current drawn from the 9.5 Vdc supply

is (see MODE 1-2) while the current drawn from the +13.8 Vdc supply (while transmitting at the

rated power) varies between 500 ma to 1500mA with temperature, operating frequency and power

supply voltage. The current drawn by the 13.8Vdc line should not exceed 1500mA. The current

drawn by the transmitter in its quiescent state depends on what modules are enabled during the

inactive (PTT off) state. This aspect of transmitter operation is controlled by jumper settings on the

transmitter Main Board (refer to the Transmitter Main Board Manual). The minimum quiescent

current is under 17ma and occurs when the Audio Processor is disabled while the transmitter is

off. If Synthesizer and Audio Processor operation is maintained continuously, the quiescent

current is approximately 80 ma.

The front panel depicted in Section 3.1 bears a DPDT toggle switch (mounted on the Front Panel

Board; see the Transmitter Main Board Manual) which controls the operation of the VT-3A130

Transmitter. When in the 'OFF' position, the transmitter is turned off; however, the 13.8 Vdc

remains on the Transmitter Main Board terminals and on the Amplifier module. When in the

'KEYED' position, +9.5 Vdc is supplied to the transmitter circuitry and the transmitter is

continuously transmitting. When this switch is in the 'NORM' position +9.5Vdc is supplied to the

transmitter circuitry although the transmitter remains quiescent until keyed from one of several

Push-To-Talk (hereafter PTT) inputs. The red indicator LED is illuminated during transmitting.

Microphone, RF output and optional reference input are mounted on the front panel; power and

other signal connections are provided by a type 'F' connector at the rear of Transmitter Main

Board. Details on their function can be found in the Transmitter Main Board Manual.

DANIELS

ELECTRONICS

VT-3A130 VHF AM Transmitter Instruction Manual

2-1