Harmonic PWRLink II 4100S Series, Руководство по эксплуатации продукта

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Fine-Tuning Each Transmitter
PWRLink™ II 4100S Series Optical Transmitter Product Manual Rev A (3/06) 4–3
Example
In the case of a transmitter with the following setup:
• Loading: 80 unmodulated NTSC channels from 45 to 550 MHz and
450 MHz from 550 to 1000 MHz -6 dBc down
• NTSC carriers RF input level: +18 dBmV per channel
• Factory optimized pad value at 15 dBmV per channel: 5.5 dB
In this example, the input level at 18 dB per channel is higher than the factory
setting of 15 dBmV per channel.
There are two options for resetting the factory settings:
• If you use MGC
⊕
Reset to Factory Settings
⇒
Pad value will be 5.5 dB.
• If you use AGC
⊕
Reset to Factory Settings
⇒
Pad value will be 5.5 +
(18-15) = 8.5 dB.
If you use MGC
⊕
Reset to Factory Settings, the pad value will be 5.5 dB.
The laser is overdriven. To optimize the transmitter’s performance, you need
to adjust the RF input level to the factory setting, 15 dBmV per channel.
Using AGC
⊕
Reset to Factory Settings provides the adequate drive level to
the laser with a pad value of 8.5 dB.
4.2 Fine-Tuning Each Transmitter
Harmonic recommends fine-tuning each transmitter to fit your specific
requirements and preferences precisely. You can modify the transmitter
configuration to trade off CNR performance for improved CSO and CTB
distortion performance.
If you increase the RF pad by 1 dB, the following results occur:
• Transmitter CNR decreases by 1 dB
• CSO decreases by approximately 1 dB
• CTB decreases by approximately 2 dB
You can adjust the RF level by using any of the three interface options.
For the RF adjustment procedure using each of the interface options, see:
• 4.4.2 Fine-Tuning the Transmitter
• 4.5 Setup via NETWatch Site Controller
• 4.6 Setup via the Transmitter’s Front Panel Controls