8

Freescale Semiconductor

MC44C402

SETTING LEVEL FOR MODULATOR/ENCODER

INTERFACE

1.

Verify calibration of the equipment. This requires a

modulator and precision signal source. The audio signal

cannot be passed through the stereo encoder for this

setup. Suggest using 10396.48 Hz audio test signal

directly into first Bessel null on a spectrum analyzer.

The null will occur at precisely 25 KHz deviation of the

10396.48 Hz audio test signal. Please see Figure 8 for

test equipment setup.

2.

Input 1800 Hz @ 0.4 V p-p into left channel and set

adjust attenuation between stereo encoder and the

modulator for optimum separation using calibrated

demodulator and decoder.

Figure 8. MC44C402 Level Setup

Audio Generator

Precision

Demoodulator

TEK 1450-1

Precision MTS Decoder

Modulation Sciences SRD1

Audio Spectrum

Analyzer

Modulator

No Audio Pre-emphasis

Stereo Encoder

Spectrum Analyzer

Audio Analyzer

Audio Precision SYS2

Wide Band

Output

Composite Video

Left In

Right In

Adjust for optimal

separation with

only Left channel

driven 1800Hz

44C402 Level Setup

Input Left Channel only

1800Hz 400 mV p-p

CVBS in

4.5MHz

Notch Filter

0db / 25KHz deviation =

1.45Vp-p @ 1KHz Mono

(both channels driven)

Demodulator / MTS Decoder Calibration

25KHz deviation Check = 1 0396 Hz

@25KHz deviation gives bessel nul l and

Ref Level on SRD-1

Composite Video

Attenuator

1) Calibrate MTS Decoder to Demodulator connection using Bess el Null Technique

2) input 1.8KHz 0.4 V p-p on left channel only and optimiz e stereo separation with

attenuator.