500 WATT RADIOBEACON TRANSMITTER
ND2000A-02x-xx0
Page 5-6
15 January 2005
(l) Oscilloscope waveform indication shall be
similar to the waveform depicted in figure 6-9,
with the negative going peaks at or slightly
below the zero volt reference line.
5.3.8
RF CARRIER CHECK:
Check that the
power amplifier and tuned RF circuits are
functioning within the required limits and verify the
RF output can be adjusted to the rated carrier level
(maximum of 500 watts), as follows:
(a) Verify requirements of paragraph 5.3.2 through
5.3.7 are completed and are being met.
(b) Verify
O/P POWER
potentiometer A4A2R48
(A5A2R48) is fully counter clockwise.
(c) Verify
PWR TRIM - LOCAL
potentiometer A4R5
(A5R5) is fully clockwise.
(d) Set switches as tabulated for
Test Setting
in
table 4-1.
(e) Set
RF
switch to
ON
.
Discontinue adjusting
O/P POWER
potentiometer
A4A2R48 (A5A2R48) if reading on
TEST-Power/Mod
meter exceeds 50 watts.
(f) Monitor reflected power indication on
TEST-
Power/Mod
meter and adjust
O/P POWER
potentiometer A4A2R48 (A5A2R48) for a
forward power indication of precisely 500 watts
on the dummy load's power indicator.
(g) Forward power level shall linearly increase,
from near zero watts to 500 watts, as
O/P
POWER
potentiometer A4A2R48 (A5A2R48) is
adjusted in step (f).
(h)
RF CURRENT-ALARM
lamp shall turn off and
TEST-Power/Mod
meter's reflected power
indication shall be near zero watts.
(i) Set
TEST-Power/Mod
switch to
FWD PWR
.
(j)
TEST-Power/Mod
meter's forward power
indication should be 500 watts.
(k) If necessary, adjust
FWD PWR CAL
potentiometer A10R79 until
TEST-Power/Mod
meter's forward power indication is precisely
500 watts.
(l) Set
TEST-Volts/Current
switch to
DC CURRENT -
SIDE A
(
B
).
(m)
TEST-Volts/Current
meter's indication shall be
between 10.7 and 14.7 amperes.
(n) Set
TEST-Volts/Current
switch to
B-V - SIDE A
(
B
).
(o)
TEST-Volts/Current
meter's indication shall be
between -49.0 and -51.0 V dc.
(p) Connect an oscilloscope to
RF MONITOR
connector.
(q) Oscilloscope waveform indication shall be
similar to the waveform depicted in figure 6-15,
with a peak-to-peak voltage between 18.0 and
22.0 volts.
(r) Adjust
O/P POWER
potentiometer A4A2R48
(A5A2R48) for the intended carrier level as
indicated on dummy load's forward power
indicator.
(s) Repeat steps (1) through (q) with the RF output
set to the intended carrier level.
5.3.9
MODULATION DEPTH (MCW)
CHECK:
Check the modulation depth with the
transmitter operating in the MCW mode as follows:
NOTE
The intended modulation depth was determined at
initial installation. It is the modulation depth a
specific antenna system will accommodate before
excessive reflected sideband power and/or distortion
is produced. It should be as close to 95% as possible.
If an intended modulation depth has not been
established, set it to 95%.
(a) Set switches as tabulated for
Test Setting
in
table 4-1.
(b) Verify
RF MON
switch A9A2S1 is set to the
position (
VOLT
or
CUR
) determined during
initial installation (see paragraph 3.13).
