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RF LEVEL ADJUSTMENT

4. RF Level Adjustment

Once you have connected the INPUT and OUTPUT ports to respectively the incoming Cable Feed and the Distribution

System, as well as Audio and Video Source Signals to corresponding Modulator Audio and Video Inputs, while monitoring the

signal level at the IVIS -20 dB RF OUT TEST Point with a Spectrum Analyzer or RF Signal Level Meter, you should be able

to measure the new Modulator’s Video and Audio carrier levels as well as the Video carrier levels for Analog signals or QAM

Power Levels for Digital signals of the existing cable system’s adjacent channels.
While monitoring the meter or analyzer, adjust the Modulator’s Video Carrier Levels by adjusting the common attenuator on

the front of the IVIS unit until you obtain an equal level as the adjacent Cable system’s Analog channel Video Carrier Level,

or 6 dB higher than the adjacent 256QAM Digital signal Power Level or 10 dB higher than the adjacent 64QAM Digital signal

Power Level. If you require additional and/or finer RF Output Level adjustment for either of the two modulators mounted in the

IVIS, adjust the RF Output Level potentiometer on the front panel of the Modulator as described in previous section.

From the factory the modulator front panel RF Output Level potentiometer is set to maximum RF output level, this will give

you the best Signal to Noise Ratio. Always attempt to make all Video Carrier Level adjustments using the common attenuator

on the IVIS front panel.

Verify that the Modulator’s Audio carrier is 15 dB below the Video Carrier. If not adjust the A/V potentiometer on the Modulator’s

front panel until the Audio to Video Ratio is set to -15 dB.
All previous measurements are to be done using a spectrum analyzer or RF signal level meter.

If using Spectrum Analyzer

for measuring Analog and Digital RF Signals: Be sure to have taken into account RBW settings

and have made corrections to the Spectrum Analyzers Reading while measuring Digital QAM Signals. Make use of Band

Power Measurement option for measuring Digital QAM signals, if supported by Spectrum Analyzer.

If using RF Signal Level Meter

for measuring Analog and Digital RF Signals: Be sure to have selected the correct

measurement mode for measuring Analog and Digital Signals.

After RF level adjustment is finished, the Video Carrier Levels of the inserted one or two new Analog signals shall equal the

Video Carrier Levels of the Cable system’s existing adjacent Analog signals Video Carriers or be 6 dB higher than adjacent

256QAM signals or be 10 dB higher than adjacent 64QAM signals.
If required, set the Audio deviation by adjusting the AUDIO potentiometer on the front panel of the modulator as described in

previous section. Also, if required, set the VIDEO Modulation depth by adjusting the VIDEO potentiometer on the front panel

of the modulator as described in previous section.

MDU Solutions

– IVIS Indoor Video Insertion System - Instalation & Operation Manual

4-1

CHAPTER 3: AGILE MODULATOR OPERATION

CHAPTER 4: RF LEVEL ADJUSTMENT

Figure #3: Functional Schematic

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