User Manual
Table Of Contents
- 1GENERAL
- 1.1Introduction
- 1.2Performance Specification
- 2THEORY OF OPERATION
- 2.1Amplifier Operation
- 2.2Power Requirements
- 2.3RF Circuitry
- 2.3.1UT-3/400 Lowpass Filter
- 2.4Power Control Circuitry
- 2.5Power Sensing Circuitry
- 2.5.1Output Power Sense
- 2.5.2VSWR Sense
- 2.5.3VSWR Overload
- 3UT-3/400 AMPLIFIER ALIGNMENT
- 3.1General
- 3.2Repair Note
- 3.3Recommended Test Equipment List
- 3.4Printed Circuitboard Numbering Convention
- 3.5Standard Factory Settings and Jumper Configuration
- 3.6UT-3/400 AmplifierAlignment
- 3.6.1General
- 3.6.2UT-3/400 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
- 4.1UT-3/400 UHF Amplifier Component Layout
- 4.2UT-3/400 UHF Amplifier Schematic Diagram
- 4.3UT-3/400 UHF Lowpass Filter Component Layout
- 4.4UT-3/400 UHF Lowpass Filter Schematic Diagram
- 5PARTS LISTS
- 5.1UT-3 / UT4 UHF Amplifier Electrical Parts List
- 5.2UT-3/400 UHF Amplifier Mechanical Parts List
- 5.3UT-3/400 UHF Low Pass Filter Electrical Parts List
- 6REVISION HISTORY
DE
DANIELS
ELECTRONICS
2-4
UHF Amplifier Instruction Manual UT-3 406 - 512 MHz
2.5.2
VSWR Sense
The VSWR sense
circuitry
uses
directional
coupler TL4 to sample some of the power
reflected
from the
antenna
terminal. The
reflected
power is
rectified
by diode D7 and
capacitor
C33 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 Q7 for open
collector
operation
(JU4 not installed, JU3 installed).
In open
collector
configuration, Q7 (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).
2.5.3 VSWR Overload
The VSWR overload
circuit
protects the UT-3/400
Amplifier
from excessive
antenna
VSWR by
reducing the amplifier's gain (output power) when an overload
condition
occurs. The VSWR
overload
circuit
(R38 to R41, R8,
U2a,
and Q4) is an extension of the VSWR sense
circuit
and
operates the same as the VSWR sense open
collector
circuit. The VSWR
Overload
Adjust
potentiometer
(R38) reduces the
voltage
level
of the VSWR
Alarm
Setpoint. The
voltage
set by
R38 is the
compared
to the output power
alarm
setpoint
by op-amp U2a which then drives
transistor Q4. When transistor Q4 turns on,
signaling
an overload condition, resistor R8 is
grounded which reduces the output power setpoint. Reducing the output power
setpoint
lowers the
UT-3/400 Amplifier's gain and protects the
amplifiers
from excessive current draw resulting from
high
antenna
VSWR.
The VSWR overload circuit's range of
adjustment
depends on the
setting
of the VSWR
Alarm
Adjust
potentiometer
(R36).
The VSWR overload transistor Q4 can be
activated
at the same point
at which the VSWR
alarm
becomes
active
or the VSWR overload
circuit
can be disabled by turning
R38
completely
counterclockwise.