Chapter 4 Transmitter Setup
Setup via HLP 4200 and HLP 4800 Display
© 2009 Harmonic Inc.
24
SPL 7110- Exx, Version 1.0, Rev A
1.
When you enter the Autosetup command via the HLP 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.
Finally, you need to select AGC or MGC mode of operation. See Section
Gain Control and Manual Gain Control
What if the loading is less than factory setup?
The Autosetup procedure will measure the RF input level and adjust the pad value for
operation as close as possible to optimum performance. When the number of analog or
digital channels is less than the factory setup and you require better CNR, you can increase
the input level by decreasing the internal RF pad value as described in section 4.2.
If you plan to add more channels in the future, Harmonic recommends that you use the
following minimum input levels to ensure that the system is easy to upgrade .
■
SPL7110S-EXX15 dBmV per analog channel
■
SPL7110C-EXX16 dBmV per analog channel
4.3.2
Automatic Gain Control and Manual Gain Control
The AGC function operates by measuring the input RF level to the transmitter and
continuously adjusting the RF pad to maintain constant drive level to the laser. When you
select AGC, the input level to the transmitter laser remains at its previously established value.
When you use AGC mode with the SPL 7110- Exx, Harmonic recommends that you drive the
transmitters 3 dB harder so that they can better compensate for the increased variation in the
RF input signal. For example, for 78 NTSC (System M) channels, use an RF input level of 18
dBmV/channel.
In MGC mode, the internal RF pad value of the transmitter is kept at a fixed value regardless
of the input RF level variation.
NOTE:
You can adjust the drive level of the laser in either AGC or MGC mode by changing the RF pad. For
4.2 Fine-Tuning Each Transmitter
on page 23. After you have adjusted the
pad, the transmitter will continue to operate in the same mode (AGC or MGC).
4.4
Setup via HLP 4200 and HLP 4800 Display
This section provides instructions for setting up the SPL 7110- Exx via the push buttons and
LCD display of the HLP 4200 and HLP 4800 equipment platform. To quickly and easily set up
and review the SPL 7110- Exx monitoring and control parameters, use the HLP 4200 and
HLP 4800WD front panel. For a detailed description of this interface, see Section
4.4.1
Step-by-Step Setup Instructions
1.
Verify that the SPL 7110- Exx module is properly installed in the HLP platform.
Instructions are provided in Section
2.2 Installing the Transmitter Module
2.
Verify that the HLP 4200 and HLP 4800 is powered on and that no alarm conditions exist
within the transmitter module; make sure that the Status LED on the front panel is green.
3.
Verify that the RF input level per analog carrier is within the range set in Table 4-1 and
Table 4-2.