User Manual
Table Of Contents
- 1GENERAL
- 1.1Introduction
- 1.2Performance Specification
- 2THEORY OF OPERATION
- 2.1Amplifier Operation
- 2.2Power Requirements
- 2.3RF Circuitry
- 2.3.1VT-3/150 Lowpass Filter
- 2.4Power Control Circuitry
- 2.5Power Sensing Circuitry
- 2.5.1Output Power Sense
- 2.5.2VSWR Sense
- 2.5.3VSWR Overload
- 3VT-3/150 AMPLIFIER ALIGNMENT
- 3.1General
- 3.2Repair Note
- 3.3Recommended Test Equipment List
- 3.4Printed Circuitboard Numbering Convention
- 3.5Standard Factory Settings and Jumper Configuration
- 3.6VT-3/150 AmplifierAlignment
- 3.6.1General
- 3.6.2VT-3/150 Amplifier Adjustment
- 3.6.2.1General Set-Up
- 3.6.2.2Output Power Alarm (Forward Power)
- 3.6.2.3Output Power
- 3.6.2.4Antenna VSWR Alarm (Reverse Power)
- 3.6.2.5Antenna VSWR Overload
- 3.6.2.6Procedure Verification
- 4ILLUSTRATIONS AND SCHEMATIC DIAGRAMS
- 4.1VT-3/150 VHF Amplifier Component Layout
- 4.2VT-3/150 VHF Amplifier Schematic Diagram
- 4.3VT-3/150 VHF Lowpass Filter Component Layout
- 4.4VT-3/150 VHF Lowpass Filter Schematic Diagram
- 5PARTS LISTS
- 5.1VT-3/150 Amplifier Electrical Parts List
- 5.2VT-3/150 Low Pass Filter Electrical Parts List
- 5.3VT-3/150 Amplifier Mechanical Parts List
- 6REVISION HISTORY
DE
DANIELS
ELECTRONICS
VHF Amplifier Instruction Manual VT-3 132 - 174 MHz
2-1
1
2
THEORY OF OPERATION
2.1
Amplifier Operation
A power control
circuit
monitors the RF output power of
amplifier
U4 and keeps the power
constant. The output power from the high power
amplifier
will change as the
unregulated
+13.8
Vdc supply varies. Note that the frequency band does not change how the
amplifier
operates;
it
only changes a few
component
values in the RF circuitry.
Power for the
VT-3/150
Amplifier
is provided from the MT-3
Transmitter
Board. The
+13.8
Vdc
supply (if required) is
continuously
connected
to the
amplifier;
whereas, the
+9.5
Vdc supply is
always switched by the transmitter's PTT circuitry. The
VT-3/150
Amplifier
will not use any
power from the
+13.8
Vdc supply
until
the amplifier's
+9.5
Vdc line is switched on and an RF
input signal is present. The synthesizer or crystal control module controls the
+9.5
Vdc to the
amplifier's
circuitry;
switching it on by grounding the amplifier's input
enable
line. The
synthesizer or crystal control module will ground the input
enable
line only when the RF signal
from the synthesizer or crystal control module is phase locked. This prevents unwanted spurious
emissions during
transmitter
start-up. A
typical
start-up sequence is shown below:
1) the
transmitter
is keyed on
(+13.8
Vdc is always present)
2)
+9.5
Vdc is switched on by the PTT
circuitry
and the synthesizer
or crystal control module PTT line is pulled low
3) an RF signal is output to the
amplifier
4) the
ampli
fier's
input
enable
line is
activated
5) the
amplifier
outputs RF power
2.2
Power Requirements
Typical
current
requirements
for the
VT-3/150
Amplifier
at
different
power levels are given in the
Table
2-3 below. The current drawn from the
+9.5
Vdc supply should never
exceed
1.2 Amps
and the current drawn from the
+13.8
Vdc supply should never
exceed
1.5 Amps.
Table 2-1
VT-3/150 Amplifier Current Consumption
Output
Power
+9.5
Vdc
Supply Current
+13.8
Vdc
Supply Current
2.0 W 0.64 A 0.51 A
4.0 W 0.79 A 0.75 A
6.0 W 0.89 A 0.93 A
8.0 W 1.04 A 1.10 A
Note: Current consumption measured at 153 MHz