RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Page 5-1
15 September 2003
SECTION 5
TESTING AND ADJUSTMENTS
GENERAL
5.1
This section contains calibration
procedures that are performed in conjunction with
functional tests. Special calibration and adjustment
procedures are also included in this section.
NOTE
Instructions are presented in a step-by-step format.
Personnel who are not familiar with the detailed
circuit theory, or do not realize the impact an
adjustment will have on other steps, should follow
instructions in the order provided. It is
recommended the instructions be followed
sequentially during initial start-up and after major
repairs.
OPERATION OF EQUIPMENT
5.2
Observe the instructions presented in
section 4 when turning the system on or off. Detailed
control and indicator information is presented in
tables 4-2 through 4-9.
NOTE
A flight/range test normally determines the RF
output level required to provide the desired range
for a specific installation. This level is referred to
as the 'intended' carrier level in the following
procedures. The 'intended' carrier level must not
exceed 125 watts or be less than 25 watts. Unless
otherwise specified, the RF output should be set to
the 'intended' carrier level in the following
procedures. If an 'intended' carrier level has not
been established, set it to 125 watts (650 kHz and
less) or 100 watts (651 kHz and greater). In the
following procedures, 125 watts is referenced as
maximum RF output power for operation between
190 and 650 kHz. For operating frequencies above
650 kHz, it should be understood that the maximum
RF power setting is 100 watts.
The 'Q' of the antenna system in use will determine
the maximum acceptable modulation depth (see
paragraph 4.7). The established maximum
modulation depth, which must not exceed 95
percent, is referred to as the 'intended' modulation
depth in the following procedures. Unless otherwise
specified, the modulation should be set to the
'intended' modulation depth in the following
procedures. If an 'intended' modulation depth has
not been established, set it to the maximum
achievable percentage without causing clipping and
distortion.
TEST
meter M1's forward/reflected power scale is a
square law scale. Resulting non-linearity makes it
difficult to read less than five watts.
FUNCTIONAL TESTS/ CALIBRATION
PROCEDURES
5.3
Functional tests should be performed and
results recorded for comparison with past and future
test results; on completion of the calibration
procedures, as a routine part of scheduled
maintenance checks and as the first step in
troubleshooting procedures. Calibration tests,
performed in conjunction with the functional tests,
consist of adjusting appropriate electrical components
to bring specific operating parameters of a fully
assembled transmitter into the desired limits. The
functional tests/calibration procedures are carried out
with the transmitter's RF output connected to a
precision, 50-ohm, resistive dummy load.
NOTE
Functional tests/calibration procedures are
presented in a sequence that will accommodate a
complete functional tests and/or calibration of the
transmitter. Most procedures may be performed
independently to correct out-of-tolerance conditions
discovered during a functional test. It is
recommended a functional test be performed after
completion of any calibration procedure.
All PWB mounted potentiometers are three-turn
potentiometers that have a clutch at either extreme
of their adjustment. Their wipers must be turned a
minimum of three turns in the required direction to
ensure they have been set fully clockwise or fully
counter clockwise.
5.3.1
FUNCTIONAL
TESTS/CALIBRATION TEST EQUIPMENT
:
The following test equipment is required for the
functional tests/calibration procedures. Refer to table
1-3 for additional information regarding test
equipment identification and/or specifications.
