RADIOBEACON TRANSMITTER
ND500II (125 WATTS) DOUBLE SIDEBAND - NO VOICE
Page 3-9
15 September 2003
WARNING
3.10.2
The second stage consists of a complete
calibration and tuning of the antenna system's tuned
stages (normally an automatic antenna tuning unit),
using the transmitter as the RF power source and the
system antenna as the radiating element.
3.10.3
The third stage consists of performing a
functional test of the transmitter when it is connected
to a properly tuned antenna system. Where range is
the operating criteria in lieu of rated power, range
tests should be conducted to determine the carrier
level that will provide the desired range. Where the
'Q' of the antenna system imposes sideband
limitations, the maximum modulation depth that can
be used without clipping and/or distortion should be
determined.
This transmitter contains many solid state devices
that may be damaged if they are subjected to
excessive heat or high voltage transients. Every
effort must be taken to ensure the circuits are not
overdriven and they are not disconnected from
their loads while turned on. The precautionary
information included in section 4 should be read
and fully understood prior to applying power and
must be observed during operation.
FIRST STAGE (INITIAL START-UP)
3.11
The first stage of the initial start-up is to
perform a visual inspection and then perform a
complete calibration procedure as detailed in
paragraph 5.3. On completion of the calibration
procedure, perform a minimum performance test as
detailed in paragraph 5.4.
Perform the complete calibration procedure in the
order presented. Failure to follow this procedure
may result in a catastrophic failure when the
transmitter's RF output is connected to its antenna
system.
SECOND STAGE (INITIAL START-UP)
3.12
The second state of initial start-up is to
connect the transmitter's output to its antenna system,
interfaced by a suitable antenna tuning arrangement
and to calibrate the antenna tuning unit in accordance
with its instruction manual. The transmitter is used
as the 50-ohm, RF signal source and the following
should be observed:
Do not turn on transmitter until requested by
personnel at the antenna site. Potentially lethal
RF voltages are present in the antenna tuning unit
when an RF signal of any level is being applied.
(a)
Verify the requirements of paragraph 3.11 have
been satisfactorily completed.
(b)
Set all transmitter switches, except
POWER
switch S3, to positions tabulated for
'Calibration Setting' in table 4-1.
(c)
Set
POWER
switch S3 to
OFF
.
(d)
Connect an antenna system, interfaced by a
suitable antenna tuning arrangement, to RF
output coaxial connector A7J2, using a suitable
50-ohm coaxial cable.
(e)
Set or verify
O/P PWR
potentiometer A4R31 is
set fully counter clockwise.
(f)
Set or verify
MOD %
potentiometer A4R31 is
set fully counter clockwise.
(g)
Set
TEST
switch S6 to
FWD PWR
.
(h)
When requested by personnel at antenna tuning
unit site, set
POWER
switch S3 to
ON
and
adjust
O/P PWR
potentiometer A4R31
clockwise for an initial
FWD PWR
indication of
10 watts on
TEST
meter M1.
(i)
Continuously monitor the forward power
indication on
TEST
meter M1 and adjust
O/P
PWR
potentiometer A4R31 to control the RF
output level during calibration of the antenna
tuning unit as requested by personnel at the
antenna tuning unit site. Do not permit the
forward power indication on
TEST
meter M1 to
exceed 125 watts (the maximum rated carrier
power of the transmitter).
