RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Page 5-16
15 September 2003
5.4.2
LOW VOLTAGE POWER SUPPLY
ON/OFF PWB AC MONITOR CALIBRATION:
Calibrate the threshold of the AC monitor circuitry as
follows:
(a)
Verify the requirements of paragraphs 5.3.2
through 5.3.13 have been completed.
(b)
Turn off the transmitter and connect an AC
variac to act as the transmitter’s AC power
source. Turn on transmitter and adjust variac
for nominal operating voltage.
(c)
Set
LOW AC INHIBIT
jumper A1A1E1, on low
voltage power supply on/off PWB to the
AC
position (shorting pins 1 and 2).
(d)
Set
LOW AC
potentiometer A1A1R13, on low
voltage power supply on/off PWB, fully
counter clockwise.
(e)
Adjust variac until AC power source is 10%
below the nominal level.
(f)
Adjust
LOW AC
potentiometer A1A1R13
clockwise until the
BATTERY ALARM
lamp just
turns on.
(g)
Turn off the transmitter and disconnect the AC
variac. Reinstall the transmitter’s normal AC
power connector. Restore transmitter to
operation.
OPERATIONAL ADJUSTMENT PROCEDURES
5.5
Operational adjustments are those
procedures that are routinely performed by
maintenance personnel when the transmitter's RF
output is connected to its antenna system after
successful completion of a minimum performance
test and when emission levels/quality are being
confirmed. It is assumed the antenna system has
been properly tuned and is presenting a 50-ohm load
at the carrier frequency.
NOTE
Reference is made to 'intended' carrier level. This
level is normally established by a flight check
during initial installation. The 'intended' carrier
level must not exceed 125 watts under any
circumstances.
5.5.1
OPERATIONAL ADJUSTMENT
TEST EQUIPMENT
: The following test equipment
is required for operational adjustment procedures (see
table 1-3 for more detailed specifications):
(a)
A frequency counter with suitable test probes
(BNC coaxial connector terminated with
clip-on probes).
(b)
An oscilloscope with suitable test probes (BNC
coaxial connector terminated with clip-on
probes).
(c)
A digital multimeter with appropriate test leads.
5.5.2
OPERATIONAL ADJUSTMENT
PREREQUISITES
: The following prerequisites
must be completed before attempting operational
adjustments:
(a)
Verify the functional tests/calibration
procedures, detailed in paragraphs 5.3 through
5.3.13, have been successfully completed.
(b)
Connect or verify the transmitter's RF output
(A7J2) is connected to a properly tuned 50-ohm
antenna system.
(c)
If using an AC power source, verify its voltage
is within five percent of the mean RMS voltage
used to select the primary winding taps of
power transformer A1T1 in paragraph 3.8.3.1
and it has a minimum power rating of 350
volt-amperes. If using a DC power source,
verify it is within
±
2V of its nominal DC
voltage.
(d)
Verify the test equipment identified in
paragraph 5.5.1 is available.
(e)
Set switches as tabulated for
Calibration
Setting
in table 4-1.
(f)
Set
POWER
switch S3 to
OFF
.
(g)
Remove or verify the top cover is removed from
the transmitter.
(h)
Set
O/P PWR
potentiometer A4R31 fully
counter clockwise.
