RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Page 5-10
15 September 2003
(a)
Verify requirements of paragraph 5.3.8.1 have
been completed.
(b)
Determine the 'minimum' acceptable RF carrier
level, normally -3.0dB, before the transmitter
shuts down and record this level, in watts, as
the 'Low Carrier Level Fault Threshold' in
Established References
section of table 5-2.
NOTE
Refer to 'Power' column of table 5-1 to determine
multiplication factor and then multiply 'intended'
carrier level by this factor to determine the
minimum carrier level; when reduction is specified
in dBs.
(c)
Adjust
O/P PWR
potentiometer A4R31 for the
low carrier level fault threshold determined in
step (b), as indicated by dummy load's power
indicator.
(d)
Simultaneously monitor
THRESH
lamp A5DS1
and slowly adjust
LOW CARRIER
potentiometer
A5R10 clockwise, during portion of keying
frame that contains identification code, until
THRESH
lamp A5DS1 just turns full on.
(e)
Adjust
O/P PWR
potentiometer A4R31 for the
'intended' carrier level, as indicated by dummy
load's power indicator.
5.3.8.3
High Carrier Level Fault Threshold
Calibration
: Set the carrier level fault threshold to
the level that will shut down the transmitter when the
RF output has increased 2.0dB or to a user
determined maximum level, as follows:
NOTE
International Civil Aviation Organization (ICAO)
standards dictate the transmitter be turned off or a
warning alarm be generated when the RF output has
increased by 2.0dB or more from the intended
carrier level. The following procedures use +2.0dB
as the carrier fault threshold level. If the user
decides to select a different threshold level, the user
selected threshold level should be inserted where
+2.0dB is referenced.
A higher power rated dummy load (minimum 400
watts) is required to perform this calibration.
(a)
Verify requirements of paragraph 5.3.8.1 have
been completed.
(b)
Determine the 'maximum' acceptable RF carrier
level, no2.0dB, before the transmitter
shuts down and record this level, in watts, as
the 'High Carrier Level Fault Threshold' in
Established References
section of table 5-2.
NOTE
Refer to 'Power' column of table 5-1 to determine
multiplication factor and then multiply 'intended'
carrier level by this factor to determine the
minimum carrier level; when reduction is specified
in dBs.
(c)
Adjust
O/P PWR
potentiometer A4R31 for the
high carrier level fault threshold determined in
step (b), as indicated by dummy load's power
indicator.
(d)
Simultaneously monitor
THRESH
lamp A5DS1
and slowly adjust
HIGH CARRIER
potentiometer
A5R89 counterclockwise, during portion of
keying frame that contains identification code,
until
THRESH
lamp A5DS1 just turns full on.
(e)
Adjust
O/P PWR
potentiometer A4R31 for the
'intended' carrier level, as indicated by dummy
load's power indicator.
5.3.8.4
Modulation Depth Fault Threshold
Calibration
: Set the modulation depth fault threshold
to the level that will shut down the transmitter when
the modulation depth has decreased 4.0dB or to a
user determined minimum depth, as follows:
NOTE
The modulation depth fault threshold (normally
-4.0dB) must be a minimum of 1.0dB greater than
the carrier level fault threshold.
(a)
Verify requirements of paragraphs 5.3.8.1
through 5.3.8.3 have been completed.
(b)
Determine the 'minimum' modulation depth
(normally -4.0dB when the carrier level fault
threshold is -3.0dB) that is acceptable before
the transmitter is shut down. Record this level
as the 'Modulation Depth Fault Threshold' in
Established References
section of table 5-2.
