PAL SYSTEM TELEVISION MEASUREMENT : V. TRANSMITTER MEASUREMENTS

V. TRANSMITTER MEASUREMENTS

In this section, we discuss two parameters which should be monitored and adjusted at the transmitter depth of modulation and ICPM. These two measurements are commonly made with time domain instruments
such as waveform monitors or oscilloscopes. Most of the other tests for characterizing transmitter performance are made with a spectrum analyzer and are not addressed in this publication.
In order to make these measurements, a high-quality demodulator such as the Tektronix TV1350 or 1450 is required.
These instruments provide envelope and synchronous detection demodulation. Unlike envelope detectors, synchronous detectors are not affected by the quadrature distortion inherent in the vestigial sideband transmission system. For measurement purposes, the effects of quadrature distortion should be removed so
as not obscure distortions from other sources. A quadrature output is available when the instrument is operating in the synchronous detection mode.
Envelope detection is most similar to the demodulation used in most home receivers and is also available in the TV1350 and 1450.
The TV1350 and 1450 produce a zero carrier reference pulse which provides the reference level required for depth of modulation measurements. This pulse is created at the demodulator output by briefly reducing
the amplitude of the RF signal to the zero carrier level prior to demodulation.


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Table of Contents

Preface	3
Good Measurement Practices	4
EQUIPMENT REQUIREMENTS	4
CALIBRATION	6
INSTRUMENT CONFIGURATION	6
DEMODULATED RF SIGNALS	8
TERMINATION	8
DEFINITION OF THE PAL TELEVISION STANDARD	8
PERFORMANCE GOALS	8
Waveform Distortions and Measurement Methods	9
I VIDEO AMPLITUDE AND TIME MEASUREMENTS	9
Amplitude Measurements	10
Time Measurements	12
SCH Phase	15
II LINEAR DISTORTIONS	18
Chrominance-to-Luminance Gain and Delay	19
Short Time Distortion	24
Line Time Distortion	26
Field Time Distortion	28
Long Time Distortion	30
Frequency Response	31
Group Delay	36
K Factor Ratings	38
III NONLINEAR DISTORTIONS	41
Differential Phase	42
Differential Gain	46
Luminance Nonlinearity	50
Chrominance Nonlinear P h a s e	5 2
Chrominance Nonlinear Gain	5 3
Chrominance-to-Luminance Intermodulation	54
Transient Sync Gain Distortion	55
Steady-State (Static) Sync Gain Distortion	56
IV NOISE MEASUREMENTS	57
Signal-to-Noise Ratio	58
V TRANSMITTER MEASUREMENTS	6 0
ICPM	61
Depth of Modulation	63
GLOSSARY OF TELEVISION TERMS	64
APPENDICES
APPENDIX A - PAL COLOUR BARS	67
APPENDIX B - SINE-SQUARED PULSES