RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Page 5-11
15 September 2003
NOTE
If difference between 'intended' modulation depth
and 'minimum' modulation depth is specified in dBs,
refer to table 5-1 and determine 'Voltage'
multiplication factor for specified dB reduction.
Multiply 'intended' modulation depth by 'Voltage'
multiplication factor to determine 'minimum'
modulation depth.
(c)
Verify the RF output is the 'intended' carrier
level, as indicated by dummy load's power
indicator.
(d)
Adjust
MOD %
potentiometer A4R2 for the
modulation depth fault threshold determined in
step (b), as indicated by modulation envelope
on oscilloscope waveform.
(e)
Simultaneously monitor threshold lamp A5DS1
and slowly adjust
MOD THRESH
potentiometer
A5R8 clockwise, during coded portion of
identification code, until
THRESH
lamp A5DS1
just turns fully on.
(f)
Adjust
MOD %
potentiometer A4R2 for a
modulation depth of 95%, as indicated by
modulation envelope on oscilloscope waveform.
5.3.8.5
Loss of Keying/Shutdown Delay
: Verify
the loss of keying will cause a shutdown and the
shutdown delay period has been set to the time
required to ensure a fault has occurred before the
transmitter shuts down, as follows:
NOTE
The shutdown delay will normally be set to its
minimum (nominally 20 seconds) when each eight-
second frame, of the octal frame sequencer, contains
identification code. It is recommended that
shutdown delay be extended to include a minimum
of two identification code frames if one or more CW
and/or MCW frames are included in the keyer frame
sequencing.
(a)
Verify requirements of paragraphs 5.3.8.1
through 5.3.8.4 have been completed.
(b)
Determine the time required to monitor two full
eight-second keyer frames that contain
identification code (refer to paragraph 3.8.4.2).
Record this time as the 'Shutdown Delay' in
Established References
section of table 5-2.
(c)
Verify the RF output is the 'intended' carrier
level, as indicated by dummy load's power
indicator.
(d)
Verify the modulation envelope is the 'intended'
modulation depth, as indicated by the
oscilloscope waveform; and it is being keyed
during keyer frames that contain identification
code.
(e)
Set
MONITOR
switch S5 to
NORMAL
(f)
MONITOR BYPASS
lamp DS2 shall turn off.
(g)
Using a stopwatch to determine shutdown delay
period, simultaneously start stopwatch and set
KEYING
switch S1 to
OFF
.
(h)
SHUTDOWN ALARM
lamp DS7 should turn on
and a remote shutdown alarm control signal
will be generated. The transmitter's RF output
should turn off within two seconds of desired
'shutdown delay' period determined in step (b).
(i)
If necessary, adjust
DELAY
potentiometer
A5R41 to meet requirements of step (h).
NOTE
The shutdown delay is adjustable between a
minimum of 20 seconds and a maximum of 80
seconds. Clockwise adjustment of
DELAY
potentiometer A5R41 decreases the 'shutdown delay'
period, counter clockwise adjustment increases the
'shutdown delay' period.
(j)
Connect a digital multimeter between A11TB1-
17 and ground and verify open circuit (high
impedance is present when
SHUTDOWN ALARM
lamp DS7 is turned on.
(k)
Set
MONITOR
switch S5 to
BYPASS
.
(l)
Momentarily set
POWER
switch S3 to
OFF
and
then return it to
ON
.
