Nautel XR12 Installation Manual

Also see for XR12: Troubleshooting manual Operation and maintenance manual Preinstallation manual

XR12 Installation Manual Commissioning tasksPage 11-2 Issue 3.0 2009-07-15Exciter RF drive board5. The default is INTERNAL RF DRIVE. See Section 8, “Audio and IBOC inputs” on page 8-1and Section 10, “Other considerations” on page 10-1 for information on using an externalRF drive source.Internal/external RF drive source6. RF synthesizer PWBs can use their integral RF oscillator, or an external RF generator, astheir RF drive source. Verify that the transmitter is configured to use the desired RF drivesource.Audio Lowpass Filter7. The remote interface PWB A2A6 on the exciter panel allows you to select one of four audiobandpass 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 defaultselection provides a -1.0 dB roll-off at 16 kHz. This selection is suitable for mostinstallations.8. Refer to Table 11.1 to determine the available roll-off frequencies and settings. Record theselected 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-Besselresponse is used as the low-pass audio filter. Reasons for using a lower roll-offfrequency 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 yourinstallation.Table 11.1: Audio Pass Band Selection (high frequency audio filter) switch settings(-1.0 dB) S1-1 S1-216.0 kHz CLOSED CLOSED13.5 kHz OPEN CLOSED10.5 kHz CLOSED OPEN7.5 kHz OPEN OPEN