User Manual

VHF 30W Power Amplifi er Instruction Manual
IM71-AMP3150-30
Alignment & Installation
11
CONTROL BOARD
ALIGNMENT
Refer to the VHF 30W Power Amplifi er Control
Board Component Layout Diagram for the
location of the adjustment potentiometers and
test points.
This procedure assumes the use of 1/2
wavelength RF output cables between all
pieces of test equipment after the PA output for
accurate power readings during mismatched
load conditions.
Step 1: Once the amplifi er board alignment is
complete, the exciter can be turned off and its
amplifi er re-connected to the local oscillator.
Next, the male connectors or test jig can be
removed from the amplifi er board and the
control board along with the front panel can be
re-connected to the power amplifi er. The power
amplifi er can then be connected via the gray
cable to the second extender card which should
be installed in the designated location within the
subrack for the power amplifi er.
Step 2: With the exciter’s output still connected
to the input of the power amplifi er and the
output of the power amplifi er still connected
through an RF coupler into a wattmeter and
50 Ohm load, set the transmitter to the desired
frequency. Next, adjust the output power of the
exciter such that the PA output is 10W. Then
adjust potentiometer RV1 until LED1, or the ‘RF
POWER’ indicator, just turns on. This threshold
may be adjusted to any RF output power level
between 10W and 30W.
Step 3: Set the exciter output power such that
the output power from the PA is equal to that
under normal operating conditions. Replace
the 50 Ohm load with a suitably rated 3:1
mismatched load. Adjust potentiometer RV2 until
LED2, or the ‘HIGH VSWR’ indicator, just turns
on.
Step 4: As a check, terminate the power
amplifi er once again with a 50 Ohm load and
ensure that LED2 is now off. If it is not off, adjust
RV2 until LED2 just turns off. Doublecheck
that the LED still activates when the output is
terminated with a 3:1 load. This threshold may
be adjusted with a 3:1 on the output of the PA
anywhere from 10W to 30W out.
Step 5: Disconnect the RF termination on the
PA such that the output is an open load. Activate
the exciter then adjust potentiometer RV3 until
LED3, or the ‘OVERLOAD’ indicator, just turns
on. When this occurs the output power is also
substantially reduced to help protect the RF
transistor. If the overload LED is turning on
without having to adjust RV3, power down the
exciter re-adjust RV3 and re-activate the exciter.
This confi rms that antenna VSWR overload
protection works correctly.
NOTE: The above three pots, RV1 to RV3, on the control
board should be re-checked and possibly re-adjusted if any of
the following changes are applied to the unit:
• The output power level is changed
• The frequency is changed
• The output cable length is changed
POWER AMPLIFIER
INSTALLATION
The AMP-3/150 RF power amplifi er is designed
for operation with any of the Daniels MT-2, MT-
3 or MT-4 VHF transmitter exciters. A complete
SR-3 subrack shipped directly from the factory
is normally set to the appropriate options and
output power calibration as requested by the
customer. These units require no tuning.
For AMP-3/150 amplfi iers shipped separately
from the SR-3 subrack, install as outlined:
- Connect +13.8V DC Power Supply to subrack
- Connect the output of the exciter to the input of
the VHF 30W PA with the cable provided
- Connect the antenna system (using a 1/2
wavelength cable if possible), turn on the PA
and key the transmitter. The ‘RF POWER’ LED
should light and the other three LED indicators
should remain off.
The LED indicators will only illuminate when the
power amplifi er is on and are defi ned as follows:
-RF POWER - Indicates that the minimum preset
RF power level is present at the power amplifi er
output. The threshold is internally adjustable
for RF output levels in the 10-30 watt range
(Factory set at 10W).
- HIGH VSWR - Alarm indicating that the load
impedance mismatch is higher than the preset
level. The threshold is internally adjustable for
load mismatches from 2:1 to an open output
(Factory set at 3:1).