Nautel XL12, Technical Instructions

Page: 46 / 238

12 000 WATT AM BROADCAST TRANSMITTER
XL12
Page 2-22
01 January 2002
Table 2-2 Primary Winding Taps for A23A2T1
NOMINAL VOLTAGE DC PWR SUPPLY PWB
(RMS, PHASE-TO-PHASE)
CONNECT
178-252 360-505 TERMINAL E3 TO
178-203 360-405 E7
204-223 406-450 E6
224-234 451-475 E5
235-252 476-505 E4
2.3.2 EXCITER RF DRIVE PWB OPTIONS:
There are a number of options for the printed wiring
boards which provide the RF drive for the 'A' and 'B'
exciters. Identify and record which option has been
installed for exciter 'A' and for exciter 'B', noting
they are located on the exciter panel:
NOTE
If a C-QUAM AM stereo PWB is installed to
provide exciter A's RF drive, it is located on the
rear of the exciter panel in its A2A2 position. In
this case, a PWB will not be installed in the
exciter panel's A1A1 position.
2.3.2.1 Exciter A's RF Drive PWB :
One of
three RF drive PWBs will be installed on the exciter
panel (A2) to provide exciter A's RF drive. They
are:
NAPE68 RF Drive PWB (standard).
NAPE60 Frequency Synthesizer PWB.
NAPE49 C-QUAM AM Stereo Exciter PWB.
2.3.2.2 Exciter B's RF Drive PWB :
One of two
RF drive PWBs will be installed in the exciter panel's
A1A4 position to provide exciter B's RF drive. They
are:
NAPE68 RF Drive PWB (standard).
NAPE60 Frequency Synthesizer PWB. (A1A4).
2.3.3 INTERNAL/EXTERNAL RF DRIVE
SOURCE:
RF drive and frequency synthesizer
PWBs have provision to use their integral RF
oscillator or an external RF generator as their RF
drive source. The user must identify which RF drive
source is to be used and then configure or verify the
installed PWB is configured to use the desired
source. Refer to the
Preparation for Use
section of
the installed PWB's service instruction manual for
selection instructions. The factory default selection
is the integral RF oscillator.
NOTE
If an external RF drive is used for the 'A' and 'B'
exciters, it is recommended it be duplicated (main/
standby) and connected to changeover when a
failure occurs. If this is not the case, it is
recommended one RF drive/frequency synthesizer
PWB be connected to use its integral oscillator as
its RF drive source. This will ensure continued
operation in the event of an external RF drive
source failure.
2.3.4 FREQUENCY DEPENDENT
VARIABLES:
The printed wiring boards which
provide the RF drive for the 'A' and 'B' exciters
contain components, switch selections and/or
shorting link selections which are dependent on the
carrier frequency. Refer to the
Preparation for
Use
section of the installed PWB's service
instruction manual for selection information to verify
it has been configured for the transmitter's carrier
frequency.
NOTE
Factory installed PWBs will be configured for the
frequency that was identified in contract
documents and will be precisely calibrated for
optimum operation when the transmitter is
operating into a 50-ohm load. Do not change
any adjustment, link selection or switch setting
other than those specified in these
Technical
Pre-commissioning Procedures or the
Commissioning Procedures of paragraph 2.4.
The optimum variable pulse duration modulation
frequency
(
ƒ
PDM
)
was selected during factory
tests. Refer to the Transmitter Configuration
Sheet
,
provided with the Factory Test Results , to
determine switch settings that were established to
obtain this frequency. These settings should be
used unless the assigned carrier frequency is
changed.