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500 WATT RADIOBEACON TRANSMITTER
ND2000A-02x-xx0
Page 5-15
15 January 2005
(al)
MONITOR-BYPASS
lamp A1A1DS8 shall turn
off and selected side
A
or
B
shall remain on.
(am) After the delay determined in step (c), the
selected side (main) transmitter will turn off and
STANDBY-ALARM
lamp shall turn on (see note
after step (k).
(an) Set
RF
switch to
OFF
and
MONITOR
switch to
BYPASS
.
(ao) Set
KEYING
switch A4S1 (A5S1) to
OFF
.
(ap) Set
RF
switch to
ON
.
(aq) Adjust
TONE LEVEL
potentiometer A4A2R19
(A5A2R19) for the intended modulation depth,
as indicated by
TEST-Power/Mod
meter.
5.3.16 SWR CUTBACK THRESHOLD
CHECK:
Check that SWR cutback threshold level
represents a reflected power of 55 watts, as follows:
(a) Set switches as tabulated for
Test Setting
in
table 4-1.
(b) Set
O/P POWER
potentiometer A4A2R48
(A5A2R48) fully counter clockwise.
(c) Verify
RF
switch is set to
OFF
.
(d) Disconnect connector P13 from A9A2J1 and
P14 from A9A2J2 (refer to figure MD-30 to
locate fwd/refld power probe A9A2).
(e) Install connector P14 on connector A9A2J1.
(f) Connect a shorting clip across resistor
A4A2R44 (A5A2R44).
(g) Set
RF
switch to
ON
.
(h) Simultaneously monitor dummy load's power
indicator and
SWR-ALARM
lamp while slowly
adjusting
O/P POWER
potentiometer A4A2R48
(A5A2R48) clockwise until
SWR ALARM
lamp
just turns on.
Discontinue adjusting
O/P POWER
potentiometer
A4A2R48 (A5A2R48) when dummy load's forward
power indication exceeds 60 watts.
(i)
Dummy load's forward power indication should
be 55 watts.
(j)
If requirement of step (i) is not met, adjust
O/P
POWER
potentiometer A4A2R48 (A5A2R48)
for precisely 55 watts as indicated by dummy
load's forward power indication.
(k) Set
TEST-Power/Mod
switch to
REFL PWR
.
(l)
TEST-Power/Mod
meter's indication shall be 55
±5.0 watts.
(m) Adjust
SWR CUTBACK THRESHOLD
potentiometer A10R95 until
SWR-ALARM
lamp
just turns on.
(n) Connect a multimeter, which has been set to
measure resistance between TB3-13 and
ground.
(o) Multimeter indication (
SWR Alarm
) shall be
zero ohms.
(p) Connect a multimeter, which has been set to
measure resistance, between TB3-10 and
ground.
(q) Multimeter indication (
SWR Standby
) shall be
zero ohms.
(r) Set
O/P POWER
potentiometer A4A2R48
(A5A2R48) fully counter clockwise.
(s)
SWR-ALARM
lamp shall turn off.
(t) Remove shorting clip from resistor A4A2R44
(A5A2R44).
(u) Slowly adjust
O/P POWER
potentiometer
A4A2R48 (A5A2R48) clockwise until
SWR-
ALARM
lamp just turns on.