TDA5667-5 Datasheet, PDF (14/22 Pages) Siemens Semiconductor Group – Video Modulator for FM/AM-Audio

TDA 5667-5
Test Circuit 4
Description of the Measurement Configuration to Measure the Audio and/or Noise
in Video during FM- and AM-Modulation of the Audio Carrier
Calibration: AF-signals are switched off, video signal is present at video input, modulation
measurement device set at AM is adjusted to video carrier; filter: 300 Hz...20 kHz;
detector: (P+P)/2; Wave analyzer at video signal level (16 kHz) adjusted and
resultant level as reference a_v defined.
1) Measurement of audio interference product ratio in video while the audio carrier FM modulated:
AF-signal is connected to FM-audio input; video signal is present at video input; Modulation
measurement device set at AM; filter: 300 Hz...20 kHz; detector: (P+P)/2; the automatic RF-level
position of the measurement device is switched off; wave analyzer at video signal level 1 kHz or
2 kHz or 3 kHz adjusted and resultant level is set to a_A. The audio noise ratio in video results
from a_A/V = a_A-a_V (dB).
2) Measurement of signal-to-noise ratio in video without FM-modulation of audio carrier: AF-signals
are switched off; video signal is switched on; modulation measurement device set at AM; filter:
300 Hz...3 kHz; detector: RMS ^x 2 ; Wave analyzer at video signal level (16 kHz) detuned; read
out in dB to reference level of calibration is a_N/V.
3) The noise limit of the measurement device is approx. 85 dB.
Semiconductor Group
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