NV30/NV40 Operations and Maintenance Manual Non-standard maintenance
Page 4-4 Issue 3.3 2014-12-10
Improving transmitter performance for IBOC presets
After a power or frequency change to an operating FM+HD or HD preset, optimize the transmitter’s
performance as follows:
Parts and tools
– Transmitter’s AUI
Preliminary checks
1. Verify the transmitter is operating without fault at the licensed RF output power in FM+HD
or HD mode, with standard modulating audio present.
2. Observe (maximize the display size) and save the AUI’s existing Spectrum intrument panel
(set to display transmitter output) and record the meter readings for Controller - DC-RF
Efficiency and Controller - PA Volts (see “Identifying meter information on a specific sub-
device” on page 2-42). Save the Spectrum display by remotely connecting to the AUI and
using your keyboard’s Print Screen button to copy the image, then paste the image into a
compatible application (Paint, Word, etc.). The spectrum plot should indicate at least 3 dB of
margin between the IBOC intermodulation products and the blue mask limit lines (see
Figure 4.1 on page 4-5). Maximize the spectrum display size and measure points on the
spectrum plot using the cursor (see “Spectrum Analyser” on page 2-30 for details).
Improving performance
1. From the transmitter’s AUI, select Local control and then go to the Menu - Presets page.
The active preset is displayed.
2. Click in the HD PA Volts field in the Mode section (see Figure 4.1 on page 4-5) and reduce
the voltage value by 1 V (e.g., change 48.0 to 47.0). Press
Activate.
3. Observe the Spectrum intrument panel again. Repeat Step 2, as necessary, until the
Spectrum’s intermodulation products are within 3 dB of the blue mask limit line or at
-77 dBc.
4. Verify that the Controller - DC-RF Efficiency meter reading has increased from the value
recorded in Step 2 of “Preliminary checks”.
5. Repeat this procedure for all FM+HD or HD presets and if the licensed power level
changes.
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