500 WATT RADIOBEACON TRANSMITTER
ND2000A-02x-xx0
Page 5-1
15 January 2005
SECTION 5
TESTING AND ADJUSTMENTS
GENERAL
5.1
This section contains adjustment
procedures that are performed in conjunction with
functional tests. Special and operational adjustments
procedures are also included in this section.
NOTE
Instructions are presented in a step-by-step format. It
is recommended that personnel who are not familiar
with detailed circuit theory or do not realize what
impact a specific adjustment will have on other steps,
follow instructions in the order presented. It is
recommended 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 4-10.
NOTE
TEST-Power/Mod
meter's forward/reflected power
scale is a square law scale. Resulting non-linearity
makes it difficult to read less than 50 watts. Any
reading that is less than fifty percent of the 50 watt
mark is less than 12.5 watts.
The carrier portion of the RF output is referred to as
the intended carrier level in the following procedures.
This level is normally determined by flight/range tests
during initial installation (refer to paragraph 3.13).
The intended carrier level must not exceed 500 watts
or be less than 100 watts. Once established, the RF
output power that provides the desired field strength
at the specified range shall be used as the intended
carrier level. Use 500 watts as the intended carrier
level if flight/range tests have not been completed.
The depth of the modulation envelope is referred to as
the intended modulation depth in the following. The
modulation depth is normally dictated by the 'Q' of the
antenna system and is determined during initial
installation (refer to paragraphs 4.7 and 3.13). The
intended modulation depth should be as close to 95
percent as is possible. Once determined, the optimum
modulation percentage that can be attained from a
specific transmitter/antenna system shall be used as
the intended modulation depth. Use ninety-five
percent as the intended modulation depth, if no other
value has been established.
TEST/ADJUSTMENT PROCEDURES
5.3
Functional
test/adjustment procedures shall
be performed and the results recorded for comparison
with past and future test results, as a routine part of
scheduled maintenance checks and as the first step in
troubleshooting procedures. The adjustment
procedures, 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 test/adjustment
procedures are carried out with the transmitter's RF
output connected to a precision, 50 ohm, resistive
dummy load.
NOTE
Functional test/adjustment procedures are presented
in a sequence that will accommodate a complete
functional test and/or alignment of transmitter.
Printed wiring board (PWB) mounted potentiometers
are four-turn potentiometers that have a clutch at
either extreme of their adjustment. Their wipers must
be turned a minimum of four turns in one direction to
ensure they have been set fully clockwise or fully
counter clockwise.
