Évaluations - 1, GPA: 4
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Facilité d'utilisation
When the instrument is in NICAM mode and the FM modulation is switched off (for example, by selecting the external modulation or by switching off the FM carrier), the RSSF bit is automatically set to LOW. The TEST key selects three special data sets. The TEST key has a stepping function and by repeatedly pressing the key, the signals DATA 1 - DATA 2 - DATA 3 are switched on. For DATA 3, both LEDs next the key are lit. The data sets do not comprise real NICAM data; they contain bit patterns to enable the check of NICAM modules. The data sets are as follows: DATA 1 NICAM demodulator test DATA 2 NICAM decoder test DATA 3 unmodulated carrier In the test mode only the unmodulated FM sound carrier is available. 10.2.3 Applications The color TV pattern generators including NICAM sound make it possible to check conventional TV sets with analog sound facilities in mono, dual, and stereo modes. In addition the NICAM-728 signal allows you to check the complete digital sound channel in the same operating modes. By selecting different NICAM amplitudes (AMPL LOW/AMPL high) you can check the expander of the NICAM decoder. In this part the scale factors are recovered and an expansion of the audio data from 10 to 14 bits is realized. For checking the de-emphasis of the NICAM receiver you can use the 1 kHz and 3 kHz sound frequencies. It is possible to select the RSSF bit for all NICAM modes. By doing this, switching from NICAM to analog sound can be checked in the receiver. Test functions The test signals are ideally suited for checking single functions or circuitries in the sound part of NICAM receivers (see Fig. 1 block diagram of a NICAM receiver for TV sets). The test signal DATA 1 is used for checking the 4QPSK demodulator. By this method atriggerable signal at the data output of the NICAM demodulator circuit TDA 8732 can be displayed on the screen of an oscilloscope. The subsequent circuit SAA 7280 (Terrestrial Digital Sound Decoder) in this case sends an error message (error flag) and thus indicates faulty NICAM data. PM 5415 / PM 5418 NICAM DIGITAL SOUND / STEREO SOUND (GB) 10-7 1^ (to MICROPROCESSOR) Fig. 1 NICAM Receiver for TV Set (Philips) Similar circuit design is also used by other manufacturers, for example the demodulator circuit from Toshiba TA 8662N or the decoder circuit CF 70123 from Texas Instrument. The test DATA 2 checks NICAM decoders, for example it sends a continuous 32 kHz square wave signal at the l2S bus output of the SAA 7280, which can easily be displayed on the screen of an oscilloscope. Test DATA 3 sends an unmodulated NICAM sound carrier that is suited for adjustment and level measurements. 10-8 NICAM DIGITAL SOUND / STEREO SOUND PM 54Î5 / PM 5418 10.3 10.3.1 10.3.2 CHARACTERISTICS Video Part Video modulation TV systems Polarity RF sync, level RF blanking level RF white level Chroma Part PAL/NTSC TV systems Subcarrier frequency - Tolerance - Temperature drift - Aging Subcarrier frequency - Tolerance AM all except L SECAM L negative positive 100% 5... 20 % 30% 10...30% 100% B,D,G,H,I,M,N M 4.433619 MHz 3.579545 MHz 3.575611 MHz 3.582056 MHz <1 ppm 2 ppm 2 ppm/year 4.433619 MHz <100 ppm internal/external switchable SECAM only PM 5418 PAL NTSC coupled with line frequency according to system selected PAL B,D,G,H,I NTSC PALM 1 only PM 5418 TDSI PAL N J at 23 °C system NTSC/4.433 MHz; not coupled with line frequency at 23 °C Subcarrier blanking according to TV system PM 5415/PM 5418 NICAM DIGITAL SOUND / STEREO SOUND 10-9 10.3.3 Sound Part Analog AM/FM sound (analog) see analog stereo sound, Section 9.3 Following additions and changes: Sound carrier frequency Sound carrier 1 Tolerance Temperature drift Aging 4.5 MHz 5.5 MHz 6.0 MHz 6.5 MHz <1 ppm 2 ppm 2 ppm/year on/off switchable; coupled with line frequency system M,N B,G,H I D,K,K1,L (SECAM sound system only PM 5418) at 23 °C FM frequency modulation FM INTERN 1 kHz ±3 ppm 3 kHz ±3 ppm FM deviation 15 ±5 kHz 30 ±6 kHz 31 ±6 kHz 27 ±6 kHz Sound carriers Carrier 1 FM deviation (B/G) 30 ±6 kHz 15 ±3 kHz 30 ±6 kHz Carrier 2 30 ±6 kHz 30 ±6 kHz system M,N B,G,H I D,K,K1 internal source 1 kHz, measured with deemphasis DUAL, 1 kHz STEREO, right carrier off STEREO, both carriers on Modulation of the AM/FM sound carriers, NICAM off see Section 9.3, except specifications in this section. Modulation of the AM/FM sound carrier, NICAM on AM/FM MONO carrier remains, FM STEREO carrier off sound carrier 1 sound carrier 2 Sound carrier 2 5.7421875 MHz system PAL B,G - Tolerance <3 ppm 10 - 10 NICAM DIGITAL SOUND / STEREO SOUND PM 5415 / PM 5418 10.3.4 Internal MONO and DUAL STEREO FM deviation Sound channel 1 Sound channel 2 - Tolerance channel 1, 2 Test mode same contents as NICAM channel 1 sum of NICAM channel 1 + 2 ±30 kHz 1 kHz or 3 kHz 1 kHz <3 ppm modulation off sinewave, on/off switchable sinewave, on/off switchable for the NICAM-Te...
Ce manuel est également adapté pour les modèles :Electricité - PM5415 (35.7 mb)
Electricité - PM5415 (35.7 mb)
Electricité - PM5418 (35.7 mb)