Transmitter Setup
4–4
Copyright © 2002 Harmonic Inc.
4.3.1
Autosetup
What does Autosetup achieve?
The Autosetup feature calibrates and automatically adjusts the internal
RF pad for very close-to-optimum modulation performance.
How does Autosetup operate?
Figure 4-1. Autosetup via the HLP 4200 front panel
The Autosetup procedure works in three steps:
1. When you enter the Autosetup command via the HLP 4200WD front
panel, the transmitter’s internal microprocessor measures the input drive
level to the transmitter. Then, it sets the attenuator pad so that the average
RF drive level to the laser is at the same optimal value determined at the
Harmonic factory using CW carriers.
2. Once this is done, the menu asks you to choose between CW Mode and
Video Mode.
- By entering CW Mode, you leave the current internal RF pad value as it
stands.
- By entering Video Mode, you add 3 dB to the current internal RF pad
value.
3. Finally, you need to select AGC or MGC mode of operation. See Section
4.3.2 Automatic Gain Control (AGC) and Manual Gain Control (MGC)
What if the video loading is less than 76 PAL B/G carriers?
When the number of video channels is below 76 and you require better CNR,
you can increase the input level as shown in Figure 4-2 on page 4-5. The
Autosetup procedure will measure the RF input level and adjust the pad
value for operation as close as possible to optimum performance.
