Codan Radio Communications AMP-3-150 Manuale Utente
VHF 30W Power Amplifi er Instruction Manual
IM71-AMP3150-30
IM71-AMP3150-30
Alignment & Installation
10
AMPLIFIER BOARD
ALIGNMENT
ALIGNMENT
Refer to the VHF 30W Power Amplifi er Board
Component Layout Diagram for the location of
the adjustment capacitors, potentiometers, air-
core coils and test points.
Component Layout Diagram for the location of
the adjustment capacitors, potentiometers, air-
core coils and test points.
This procedure assumes the use of a single
subrack with an EC-48RK extender card kit for
both the exciter and the power amplifi er such
that their internal adjustment points are easily
accessible.
Step 1: Remove the top extrusion cover from
the transmitter exciter. Set the exciter frequency
to either 143MHz or 162MHz depending upon
whether you are tuning a lowband or highband
unit, respectively.
subrack with an EC-48RK extender card kit for
both the exciter and the power amplifi er such
that their internal adjustment points are easily
accessible.
Step 1: Remove the top extrusion cover from
the transmitter exciter. Set the exciter frequency
to either 143MHz or 162MHz depending upon
whether you are tuning a lowband or highband
unit, respectively.
Step 2: Install one of the extender cards in the
designated location for the exciter within the
subrack. Connect the exciter to this extender
card using the gray connector cable provided
with the extender card kit.
designated location for the exciter within the
subrack. Connect the exciter to this extender
card using the gray connector cable provided
with the extender card kit.
Step 3: Refer to the ‘VHF 30W Power Amplifi er
Exploded View’ on page 15 for help on the
following procedures. Remove the power
amplifi er 14HP case. Next, unplug the cooling
fan from the control board and remove the front
panel. Using suitable male connectors or a test
jig, apply the following signals directly to the
amplifi er board:
Exploded View’ on page 15 for help on the
following procedures. Remove the power
amplifi er 14HP case. Next, unplug the cooling
fan from the control board and remove the front
panel. Using suitable male connectors or a test
jig, apply the following signals directly to the
amplifi er board:
• 13.8V : J3 - Pin1, Pin 2
Note: Ensure an ammeter is connected in
series with this line.
• Gnd : J3 - Pin 3, Pin 4
• 9.5V : J4 - Pin 4
• Gnd : J4 - Pin 8 (RF Input Sample)
Step 4: While monitoring the current on the
13.8V line and without an RF input to the power
amplifi er, slowly adjust the potentiometer RV1
until the current reads 230mA. As a check,
measure the voltage at TP1. It should read
between 2.5V and 3.0V.
13.8V line and without an RF input to the power
amplifi er, slowly adjust the potentiometer RV1
until the current reads 230mA. As a check,
measure the voltage at TP1. It should read
between 2.5V and 3.0V.
Step 5: Now connect the output of the exciter
to the input of the power amplifi er. Connect the
output of the power amplifi er through a suitable
RF coupler then through a power meter and
fi nally terminate the output with a 50 Ohm load.
The low power output from the RF coupler
should be connected to the input of a spectrum
analyzer. The spectrum analyzer should have
an output tracking generator capable of putting
out at least a +6dBm signal. This output should
be connected to the input of the exciter amplifi er
which is fi rst disconnected from the exciter’s
local oscillator.
to the input of the power amplifi er. Connect the
output of the power amplifi er through a suitable
RF coupler then through a power meter and
fi nally terminate the output with a 50 Ohm load.
The low power output from the RF coupler
should be connected to the input of a spectrum
analyzer. The spectrum analyzer should have
an output tracking generator capable of putting
out at least a +6dBm signal. This output should
be connected to the input of the exciter amplifi er
which is fi rst disconnected from the exciter’s
local oscillator.
Step 6: Before enabling the tracking generator,
the output power of the exciter amplifi er should
be disabled by turning its potentiometer fully
counterclockwise (~12 Turns). Now turn the
exciter on by setting the front panel switch
to ‘Key Tx’. Set the center frequency on the
spectrum analyzer to the same frequency the
exciter was set to in Step 1. Next, set the span
to 0 Hz and enable the tracking generator with a
+6dBm output.
the output power of the exciter amplifi er should
be disabled by turning its potentiometer fully
counterclockwise (~12 Turns). Now turn the
exciter on by setting the front panel switch
to ‘Key Tx’. Set the center frequency on the
spectrum analyzer to the same frequency the
exciter was set to in Step 1. Next, set the span
to 0 Hz and enable the tracking generator with a
+6dBm output.
Step 7: While monitoring the output on the
power meter and ensuring 13.8V on the PA
amplifi er board, slowly increase the exciter
amplifi er output until 30W is reached. Increase
the span on the spectrum analyzer to 20MHz.
Next, remove the cover on the low-pass fi lter
shield (10601-01) on the amplifi er PCB to
allow access to the air-core inductors, L5 to L8.
Monitoring the output response on the spectrum
analyzer, tune these inductors by altering the
spacing between the windings with a plastic
adjusting tool for maximum fl atness and gain
across the desired band (136 - 150MHz for
lowband, 150 - 174MHz for highband). Then
capacitor C12 should be adjusted for maximum
fl atness and gain also.
power meter and ensuring 13.8V on the PA
amplifi er board, slowly increase the exciter
amplifi er output until 30W is reached. Increase
the span on the spectrum analyzer to 20MHz.
Next, remove the cover on the low-pass fi lter
shield (10601-01) on the amplifi er PCB to
allow access to the air-core inductors, L5 to L8.
Monitoring the output response on the spectrum
analyzer, tune these inductors by altering the
spacing between the windings with a plastic
adjusting tool for maximum fl atness and gain
across the desired band (136 - 150MHz for
lowband, 150 - 174MHz for highband). Then
capacitor C12 should be adjusted for maximum
fl atness and gain also.
Step 8: Set the span on the spectrum analyzer
to 0 Hz and check that output VSWR is
below 1.20 on the band edges and the center
frequency of the band.
to 0 Hz and check that output VSWR is
below 1.20 on the band edges and the center
frequency of the band.
Step 9: As a fi nal check, replace the low-pass
fi lter shield and using the spectrum analyzer
again, search the band (either 136 - 150MHz
or 150 - 174 MHz) for any unwanted spurious
emissions.
fi lter shield and using the spectrum analyzer
again, search the band (either 136 - 150MHz
or 150 - 174 MHz) for any unwanted spurious
emissions.