RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Page 5-6
15 September 2003
(q)
Connect RF drive to power amplifier/modulator
A6 by connecting connector P11 to its mating
connector (A6J2).
(r)
Connect mod drive to power amplifier/
modulator A6 by connecting connector P10 to
its mating connector (A6J1).
(s)
Monitor RF output by connecting oscilloscope,
using suitable test cable, to
RF MON
connector
J1.
(t)
Set
POWER
switch S3 to
ON
and note that
requirements of steps (k), (l) and (m) in
paragraph 5.3.2.2 are met.
(u)
Oscilloscope waveform should be a straight
trace that may contain some noise.
(v)
Slowly adjust
RAMP ADJ
potentiometer A4R26
counter clockwise until a small amount of RF
output appears on oscilloscope trace.
(w)
Disconnect oscilloscope from
RF MON
connector J1 and connect between ramp
integrator test point A4TP3 and ground.
(x)
Oscilloscope indication should be similar to the
waveform depicted in example 'H' of figure 6-1.
Note the negative peaks should be at or near
ground potential.
(y)
Disconnect oscilloscope from A4TP3.
5.3.5
RF CARRIER CHECKS:
Verify the
power amplifier and tuned RF circuits are operating
within their desired limits and the RF output is
indicating the rated carrier level (maximum of 125
watts), as follows:
(a)
Verify the requirements of paragraph 5.3.2.
through 5.3.4 have been completed.
(b)
Set or verify
O/P PWR
potentiometer A4R31 is
set fully counter clockwise.
(c)
If used, set remote power trim potentiometer to
setting that will provide maximum carrier level
(a15V to A11TB1-23).
(d)
Set all switches, except
TEST
switch S6, to
positions tabulated for
Calibration Setting
in
table 4-1. Set
TEST
switch S6 to
REFL PWR
.
Discontinue adjusting
O/P PWR
potentiometer
A4R31 if reflected power reading on
TEST
meter
M1 exceeds 10 watts.
(e)
Simultaneously monitor reflected power
indication on
TEST
meter M1 and forward
power indication on dummy load's power
indicator and adjust
O/P PWR
potentiometer
A4R31 for a forward power indication of
precisely 125 watts on the dummy load's power
indicator.
(f)
TEST
meter M1's reflected power indication
shall be near zero watts.
(g)
Forward power level shall linearly increase,
from near zero watts to 125 watts, as
O/P PWR
potentiometer A4R31 is adjusted from its fully
counter clockwise position.
(h)
Set
TEST
switch S6 to
DC CURRENT
.
(i)
Indication on
TEST
meter M1's lower scale
shall be between 33 and 37 (3.3 and 3.7
'Amps') for operation between 190 and 650 kHz
or between 26 and 35 (2.6 and 3.5 ‘Amps’) for
operation above 650 kHz.
(j)
Set
TEST
switch S6 to
B+ VOLTS
.
(k)
Indication on
TEST
meter M1's lower scale
shall be between 46 and 52V.
(l)
Set
TEST
switch S6 to
FWD PWR
.
(m) Indication on
TEST
meter M1's upper scale
should be precisely 125 watts.
(n)
If necessary, adjust
FWD PWR CAL
potentiometer A5R21 to meet the requirements
of step (m).
(o)
Connect oscilloscope, using a suitable coaxial
cable, to
RF MON
connector J1.
