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
2-3
3
2.5
Power Sensing Circuitry
The
VT-3/150
Amplifier
is equipped with output power and VSWR sensing lines which can be
individually
configured as open
collector
or
linear
outputs. In open
collector
configuration, the
output is
active
low, that is, when a fail
condition
is
detected
(not enough output power or too high
antenna
VSWR) the open
collector
transistor is turned on. In
linear
configuration, a
voltage
proportional
to the sensed output power or
antenna
VSWR is output.
Both the
Output
Power
Alarm
setpoint
and the VSWR
Alarm
setpoint
are
individually
adjustable;
however, the
Output
Power Alarm
setpoint
must always be adjusted before the VSWR
Alarm
setpoint. This is because the
Output
Power
Alarm
setpoint
is used as a
reference
by the VSWR
Alarm
circuitry.
2.5.1
Output Power Sense
The output power sense
circuitry
uses
directional
coupler TL2 to sample some of the forward
power.
The sampled power is
rectified
by diode D6 and
capacitor
C20 and then
amplified
by
op-amp
U3b.
Op-amp
U3b's
amplification
is
controlled
by R21, the output power
alarm
adjust
potentiometer.
The
amplified
voltage
is then output
directly
in
linear
operation
(JU1 installed, JU2
not
installed)
or
compared
by op-amp U1a which then drives transistors Q4 and Q3 for open
collector
operation
(JU1 not installed, JU2 installed).
In open
collector
configuration, Q3 (the open
collector
output transistor) is turned on when an
alarm
condition
occurs. The
adjustment
range for the output power
alarm
can vary depending on
the
setting
of R21 (the
Output
Power
Alarm
Adjust
potentiometer).
2.5.2
VSWR Sense
The VSWR sense
circuitr
y uses
directional
coupler TL3 to sample some of the power
reflected
from the
antenna
terminal. The
reflected
power is
rectified
by diode D7 and
capacitor
C25 and then
amplified
by op-amp
U2b.
Op-amp
U2b's
amplification
is
controlled
by R36, the VSWR
Alarm
Adjust
potentiometer.
The
amplified
voltage
is then output
directly
in
linear
operation
(JU4
installed, JU3 not
installed)
or
compared
to the output power
alarm
setpoint
by op-amp U3a which
then drives transistor Q5 for open
collector
operation
(JU4 not installed, JU3 installed).
In open
collector
configuration, Q5 (the open
collector
output transistor) is turned on when an
alarm
condition
occurs. The
adjustment
range for the VSWR
Alarm
can depending on the
setting
of R36 (the VSWR
Alarm
Adjust
potentiometer).