Nautel XR12, Руководство по установке

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XR12 Installation Manual Commissioning tasks
Page 11-2 Issue 3.0 2009-07-15
Exciter RF drive board
5. The default is
INTERNAL RF DRIVE
. See Section 8, “Audio and IBOC inputs” on page 8-1
and Section 10, “Other considerations” on page 10-1 for information on using an external
RF drive source.
Internal/external RF drive source
6. RF synthesizer PWBs can use their integral RF oscillator, or an external RF generator, as
their RF drive source. Verify that the transmitter is configured to use the desired RF drive
source.
Audio Lowpass Filter
7. The remote interface PWB
A2A6
on the exciter panel allows you to select one of four audio
bandpass filters by setting the
AUDIO FILTER
switch (
S1
). Determine the most suitable roll-
off frequency and then set the
AUDIO FILTER
switch accordingly. The factory default
selection provides a -1.0 dB roll-off at 16 kHz. This selection is suitable for most
installations.
8. Refer to Table 11.1 to determine the available roll-off frequencies and settings. Record the
selected roll-off frequency and the
AUDIO FILTER
switch settings for future reference.
Note: A three-pole Butterworth filter that can be altered to provide a pseudo-Bessel
response is used as the low-pass audio filter. Reasons for using a lower roll-off
frequency are complex, but may include an antenna with sideband limitations,
square-wave overshoot, or specific properties related to the audio processing.
Nautel's field service department can provide recommendations based on your
installation.
Table 11.1: Audio Pass Band Selection (high frequency audio filter) switch settings
(-1.0 dB) S1-1 S1-2
16.0 kHz CLOSED CLOSED
13.5 kHz OPEN CLOSED
10.5 kHz CLOSED OPEN
7.5 kHz OPEN OPEN