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500 WATT RADIOBEACON TRANSMITTER
ND2000A-02x-xx0
Page 5-16
15 January 2005
(v) Simultaneously monitor
TEST-Power/Mod
meter's reflected power indication and continue
to adjust
O/P POWER
potentiometer A4A2R48
(A5A2R48) clockwise.
(w) Reflected power indication on
TEST-Power/Mod
meter shall not increase significantly beyond 55
watts as
O/P POWER
potentiometer A4A2R48
(A5A2R48) is adjusted clockwise.
(x) Set
O/P POWER
potentiometer A4A2R48
(A5A2R48) fully counter clockwise.
(y) Set
RF
switch to
OFF
.
(z) Disconnect connector P14 from A9A2J1 and
install it on A9A2J2.
(aa) Install connector P13 to A9A2J1.
(ab) Set
RF
switch to
ON
.
(ac) Adjust
O/P POWER
potentiometer A4A2R48
(A5A2R48) for the intended carrier level as
indicated by dummy load's forward power probe
indication.
5.3.17 RF CURRENT THRESHOLD
CHECK:
Verify the modulation peak detector circuit
will cause
RF CURRENT-ALARM
lamp to turn on when
the absolute maximum modulation peaks (500 watts
carrier level with modulation peaks of 100%) are
exceeded, as follows:
NOTE
The modulation peak detector (RF current) circuit has
no influence on the radiated RF output. Its sole
purpose is to alert a maintainer that the modulation
envelope is exceeding 100% when the RF output is set
to the intended carrier level.
(a) Set switches as tabulated for Test Setting in
table 4-1.
(b) Set
RF
switch to
ON
.
(c) Set
MOD
switch A4S2 (A5S2) to
ON
.
(d) Verify the RF output is the intended carrier level
and it is being modulated by the intended
modulation depth.
(e) Adjust
O/P POWER
potentiometer A4A2R48
(A5A2R48) for precisely 500 watts, as indicated
by dummy load's forward power indication.
(f) Set
TEST-Power/Mod
switch to
MOD-SET
.
(g) Adjust
SET 100 % MOD
potentiometer for 100%
modulation depth indication on
TEST-Power/
Mod
meter.
(h)
Set
TEST
-
Power/Mod
switch to
MOD-READ
.
(i) Simultaneously
monitor
TEST-Power/Mod
meter
while adjusting
TONE LEVEL
potentiometer
A4A2R19 (A5A2R19) for 100% modulation
depth indication.
(j)
RF CURRENT-ALARM
lamp shall turn on.
(k) If necessary, adjust
RF CURRENT CAL
potentiometer A10R23 until
RF CURRENT-
ALARM
lamp just turns on.
(l) Connect an oscilloscope between test point
A10TP14 and ground.
(m)
Oscilloscope waveform indication shall be
similar to the waveform depicted in figure 6-13.
(n) Simultaneously
monitor
TEST-Power/Mod
meter
while adjusting
TONE LEVEL
potentiometer
A4A2R19 (A5A2R19) for an indication that is
slightly below 100% modulation.
(o)
RF CURRENT-ALARM
lamp shall turn off.
(p) Adjust
O/P POWER
potentiometer A4A2R48
(A5A2R48) for the intended carrier level, as
indicated by dummy load's forward power
indication.
(q) Adjust
TONE LEVEL
potentiometer A4A2R19
(A5A2R19) for the intended modulation depth,
as indicated by
TEST-Power/Mod
meter.
5.3.18
ALARM SYSTEMS CHECK:
Verify
the following alarm lamps turn on when the
transmitter's parameters are not met: