Elettronika S r l TXUP500 500 Watt Analog TV Broadcast Transmitter User Manual APT139B VEGA Rev0 Date100604

Elettronika S.r.l. 500 Watt Analog TV Broadcast Transmitter APT139B VEGA Rev0 Date100604

Users manual Exciter Part 2

57_______________________________________________________________________________________________Section 3 - DiagramContents:- Cable diagram- APT139NM2 VEGA Component list- Modules description
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59Part Name Code Description QtyS0007 MODULAR STRUCTURE 1MTG0077AR0 POWER SUPPLY MODULE 1MTG0076AR0 EXTERNAL REFEREMENT MODULE 1MTG0078AR0 MULT. AUDIO STEREO MODULATOR - OPT. 1MTG0072AR0 MULT. VIDEO MODULATOR MODULE 1MTG0073AR0 MULT. IF PRECORRECTOR MODULE 1MTG0084AR0 MULT. LOCAL OSCILLATOR MODULE 1MTG0075AR0 MULT. CHANNEL FILTER MODULE 1MTG0079AR0 DISPLAY AND POWER SUPPLY MODULE 1MTF0088BR0 15W UHF AMPLIFIER MODULE 105352 SAW FILTER SF0036BA01033T (EX 523) B/G 1OPT016 OPTION NOTCH FILTER UHF VEGA 1S0007 VEGA StructurePart Name Code Description Qty05627 BOARD GUIDE cod. 010Z000 1005616 FRONT METAL SIDE M 2.5 cod. 000EA084 205552B 3-4U HANDLE KIT cod. 235.012 2DET1010 DET1010R1 DOWN DIN GUIDE FOR VEGA 105611A FRONT METAL SIDE cod. 000DA084 205611B REAR METAL SIDE cod. 000DA085 2CON0256 CON0256R0 LEFT SIDE FOR VEGA 105609A ANGULAR FOR HANDLE cod. 116ZF001 205617 REAR METAL SIDE M 2.5 cod. 000EA085 2SCH0194AR1 BUS STRUCTURE 105636A PERFORATED COVER RACK cod. 405MB084 202699 10 WAYS FEMALE CONNECTOR cod. IDS10FSR1 402867 20 CONT. FEMALE CONNECTOR cod. IDS20FSR1 402884 6 WAYS MALE KSC 6 EXTR. CLAMP-HOLDER 202881 4 WAYS MALE KSC 4 EXTR. CLAMP-HOLDER 202897 2 WAYS MALE 90° KSCO2 EXTR. CLAMP-HOLDER 1VEN00004 PAPST FAN mod. 4184NXH 24V 107596 FAN GRID LZ 201 1DET0875I DET0875R1 CONVEYER FAN FOR VEHA INOX P.2678 1CON0239 CON0239R0 RIGHT SIDE FOR VEGA 108878 RG316 50W 41626-SMB 90° 260mm DIN CABLE 108879 RG316 50W 41626-SMB 220mm DIN CABLE 208880 RG316 50W 41626-41626 120mm CABLE 3DET1056 DET1056R1 UP DIN GUIDE FOR VEGA 102513 SMB 90° R114186000 SOCKET 102515 SMB R114313000 SOCKET 108502 RG316 50W CABLE 1Component list APT139NM2 - VEGA
60MULT. AUDIO MONO MODULATOR MODULE MTG0071AR1DESCRIPTIONThe audio signal enters the module through one 600W balanced or 10kW unbalancedXLR connection, which may be placed either on the front or rear panel and software-selected. It is conditioned by a digital power-meter with a ±8dB 0.5dB-step dynamic andmuting. Then there are the emphasis and clipping stages (which can be inserted via software),before the frequency modulation of the audio carrier.The control system of the audio subcarrier is a PLL which locking frequency can be selectedvia software depending to the transmission standard, while the reference frequency comesfrom the video module.The control frequency comes from a VCTCXO inside the module to foresee the possibilityof a separated-audio system, for which the 20MHz may be locked to a more precisesystem coming from the 5/10MHz bus.The carrier obtained this way is modulated in frequency and level-conditioned by an IF gain stage trough adigital power-meter with a ±3dB dynamic in fine tuning before being added to the video carrier.The following control signal for the modulator operation are present on the board: PLL lock status of theaudio subcarrier, Overload on the audio input, Peak level of the deviation of the audio subcarrier.All of the operating parameters of the board are managed by the built-in micro-processor. Communication tooutside are performed trough RS485 bus.TECHNICAL CHARACTERISTICSInput impedance 600W - 10kW selectableNominal level 2Vpp -¥/+8dBInput Front and back XLR selectableEmphasis FLAT-50msec (FLAT-75usec)Deviation limiter SelectableLow-pass filter 15kHz excludibleFrequency response < ±0.5dBTHD < 0.5%Intermodulation < 60dB (d2,d3)Synchronous AM S/N > 50dBAsynchronous AM S/N > 70dBFM S/N CCIR > 72dBAnalog measures Carrier FM deviationCarrier frequency synthesis PLLAudio carrier characteristics On/Off selection and level adjustment > ±3dBFrequency reference Internal TCXO externally lockableExternal interface Microprocessor with RS485 protocolFirmware Re-configurable through RS485
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62The module contains the following blocks:1. Input relay  chooses the audio source between the XLR on the front panel of the module and the oneon the back of the apparatus and selects the input impedance to 600W or 10kW; both switching aremanaged by the software.2. Audio level regulation stage  regulates the level of the audio signal by means of a digital potentiometerwhich can be programmed trough a uWIRE interface (with 0.5dB step between -8dB and +8dB).3. Emphasis stage  inserts an emphasis curve on the audio signal with a time constant depending on thestandard (50,75us); the choice can be selected via software.4. Deviation limiter  cuts the audio level to limit the FM deviation; its intervention is handled by thesoftware and the intervention of the clipper, if any, is signalled by a red LED on the front panel.5. Low-pass filter  filters the audio signal before the modulation to suppress external residues from theaudio band (20Hz-15kHz); the filter can be inserted by means of jumpers on the board.6. Audio signal level measurement  this stage detects the peak level of the audio signal providing aconditioned analog voltage for the A/D conversion; the voltage will be processed by the microcontrollerof the display board (see MTG0079) to be shown as VU-METER.7. Frequency modulator  converts to intermediate frequency the audio signal as FM modulation of acarrier.8. Carrier level regulation stage  switches on and off the audio carrier and the regulation within at least±3dB of the level referring to the video carrier.9. IF amplifier  amplifies the audio carrier to obtain an output level of -6dBm.10. Output low-pass filter  filters the harmonics of the audio carrier.11. Audio IF oscillator  generates the audio carrier performing the PLL frequency synthesis; the selectablestandards and the lock indication are handled by the software.12. 20MHz reference  the frequency reference for the PLL synthesis of the carrier is generated by aTCXO which may be locked to a more precise 5/10MHz external reference (see MTG0076).13. Controller  all of the described operations are managed by a microcontroller communicating to the userinterface board (see MTG0079) by RS485 protocol; the local controller stores the status of the moduleand a reprogramming of the firmware (possible via RS485 from the display board) does not alter itscontents.
63CALIBRATION PROCEDURE- Instrument listDescription of the adjustment pointsMEASURE INSTRUMENTLock of the carriers and reference- Spectrum analyser- Oscilloscope- TesterCalibration of the audio parametersafter the FM modulation- Audio generator- FM Audio receiver- Audio parameters analyserCOMPONENT DESCRIPTIONR6 FM deviation levelR36 UnusedR37 Audio carrier level (-6dBm)R99 VU-METER deviationC17 Tuning of the local oscillator of the audio carrierL5 Fine tuning of the local oscillator of the audio carrierJ7 IF video testpoint (50kHz)J10 UnusedJ3 VCO control voltage testpoint (7...8V)J6 TCXO testpoint (50kHz)J11 UnusedJ12 External reference testpoint (100kHz)J2 Audio input (panel)J5 IF Monitor (panel)
64Component layout for adjustment points
65The calibration procedure of the module requires a complete structure of display board (see MTG0079)and extension module (see MTG0095) in order to perform the software selection which will be referredto later and power the module itself.Menu of the Multistandard Mono Audio Modulator ModuleVerification of the IF oscillator section  connect a spectrum analyser to the monitor of the J5 moduleand check the sections in it:qConfigure the module with IF On and IF Level at ½ of the scale and calibrate C17, L5 to lock the audiocarrier to the intermediate frequency of the set standard (to change the standard refer to the standardchange procedure) and obtain a lock voltage between 7V and 8V on J3, checking that SC is on Lock inthe menu of the display.qIn case of problems in obtaining the lock, check that on J6, J7 and J12 there are the frequencies listed inthe table of the description of the adjustment points.Verification of the audio base-band section  connect an audio source to J2 and an FM demodulatorwith audio parameters measurement capability to the IF monitor of J5 and check the sections in it:qConfigure the module with Audio Lvl at 0dB, Zin on 600W, Limiter off, Emph present and Sourcefront.qCalibrate R6 to obtain the correct level of audio deviation.qIncrease Audio Lvl to +6dB and set Limiter on, chect that the over LED lighted up and that Overloadindicates Pres, restore Audio Lvl to 0dB and check that the LED becomes unlit and Overload indicatesTrig, if needed reset this indication with Reset Trig and check that it goes to Abst.qCalibrate R99 for the correct indication of the VU-METER.
66Component layout SCH0198AR3 - Bot layerComponent layout SCH0198AR3 - Top layer
67MULT. AUDIO STEREO MODULATOR MODULE (Option) MTG0078AR0DESCRIPTIONThis modulator allows the Mono, Stereo and Dual Sound coding of TV audio signal.The boards accept two input audio channels with a nominal amplitude of 2Vpp ±8dB ona selectable impedance of either 600W balanced or 10kW unbalanced. The selection ofthe input impedance is made by means of a relay, the adjustment of the input level is madeby means of a digital power-meter. The audio inputs are trough balanced XLRF audioconnectors on the front panel or trough the bus connector. The audio source, either fromfront or back, is switched by a relay.The modulator allows to add a pre-emphasis circuit, which time constant can be set infactory to either 50 or 75 microseconds.It is possible to add a deviation circuit to prevent an overdrive of the modulator by anexcessive-level base-band signal.The base-band audio signals are limited in frequency through low-pass filters which suppress frequencieshigher than 15kHz.The deviation level is monitored by two peak detectors, one for each audio channel.The Mono, Stereo or Dual Sound coding is analog. The pilot tone identifying the codification is overlapped tothe audio signal which modulates the secondary audio subcarrier. This tone is represented by a 54.6875kHzpilot frequency, synthesised locally and locked by a PLL to the line frequency of the video signal in base band.The coding requires this pilot frequency to be non-modulated for monophonic audio. The pilot frequency isAM modulated with a frequency equal to 117.5Hz, 50% modulation depth, for Stereo. It is AM modulatedwith a frequency of 274.1Hz, 50% modulation depth, for Dual Sound audio.The coded audio signal modulates the two subcarriers generated by the VCO, PLL locked to a referencefrequency of 20MHz. Each of the subcarriers can be disabled, and the nominal level can be changed by±3dB. On the board there is an IF input for the 38.9MHz video carrier. The latter is added to the two audiosubcarriers and sent to the output.The following control signal for the modulator operation are present on the board:- PLL lock status of the primary audio subcarrier.- PLL lock status of the secondary audio subcarrier.- PLL lock status of the pilot tone.- Overload on the main audio input.- Overload on the secondary audio input.- Peak level of the deviation of the primary audio subcarrier.
68- Peak level of the deviation of the secondary audio subcarrier.All of the operating parameters of the board are managed by the built-in micro-processor. Communication tooutside are performed trough RS485 bus.TECHNICAL CHARACTERISTICSInput impedance 600W - 10kW selectableNominal level 2Vpp -¥/+8dBInput Front and rear XLR selectableEmphasis FLAT-50msec (FLAT-75usec)Deviation limiter SelectableLow-pass filter 15kHz excludableFrequency response < ±0.5dBTHD < 0.5%Stereo crosstalk < -40dBIntermodulation < 60dB (d2,d3)Synchronous AM S/N > 50dBAsynchronous AM S/N > 70dBFM S/N CCIR > 72dBAnalog measures FM deviation of the carriersCarrier frequency synthesis A PLLAudio carrier characteristics On/Off selection and level adjustment > ±3dBPilot tone characteristics 54687.5Hz (3/2fs) ±10HzPilot tone modulation AM 50%Modulation frequency 274.12Hz (1/57fs) 117.48Hz(1/133fs)Frequency reference Internal TCXO externally lockableExternal interface Microprocessor withRS485 protocolFirmware Re-configurable via RS485
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70The module contains the following blocks:1. Input relays (2)  chooses the audio source between the XLR on the front panel of the module and the one onthe back of the apparatus and selects the input impedance to 600W or 10kW; both switching are managed bythe software.2. Audio level regulation stages (2)  regulates the level of the audio signal by means of a digital potentiometerwhich can be programmed trough a uWIRE interface (with 0.5dB step between 8dB and +8dB).3. Emphasis stages (2)  inserts an emphasis curve on the audio signal with a time constant depending on thestandard (50,75us); the choice can be selected via software.4. Deviation limiters (2)  cuts the audio level to limit the FM deviation; its intervention is handled by thesoftware and the intervention of the clipper, if any, is signalled by a red LED on the front panel.5. Low-pass filters (2)  filters the audio signal before the modulation to suppress external residues from theaudio band (20Hz-15kHz); the filter can be inserted by means of jumpers on the board.6. Stereo matrix  encodes the two audio signals depending on the transmission mode set and adds the modulatedpilot tone to define the transmission standard as either mono, stereo or dual sound; the selection can be madevia software and is indicated by three yellow LEDs on the frontal panel.7. 14MHz quartz oscillator  generates the clock needed to synthesise the pilot tone locked to the line-synchronismfrequency of the video signal coming from the video modulator module (see MTG0072).8. Synthesised pilot tone generator  synthesises the pilot tone by means of DDS programmed trough anuWire interface.9. Audio signal level measurement  this stage detects the peak level of the audio signal providing two conditionedanalog voltages for the A/D conversion; the voltages will be processed by the microcontroller of the displayboard (see MTG0079) to be displayed as VU-METERS.10. Frequency modulators (2)  converts to intermediate frequency the audio signal as FM modulation of acarrier.11. Carrier level regulation stages (2)  switches on and off the audio carrier and the regulation within at least±3dB of the level referring to the video carrier.12. IF amplifier  amplifies the audio carrier to obtain an output level of -6dBm.13. Output low-pass filter  filters the harmonics of the audio carrier.14. Audio IF oscillators (2)  generates the audio carrier performing the PLL frequency synthesis; the selectablestandards and the lock indication are handled by the software.15. 20MHz reference  the frequency reference for the PLL-synthesis of the audio carrier is obtained from thevideo module (see MTG0072) to keep a perfect intercarrier lining.16. Controller  all of the described operations are managed by a microcontroller communicating to the userinterface board (see MTG0079) by RS485 protocol; the local controller stores the status of the module and areprogramming of the firmware (possible via RS485 from the display board) does not alter its contents.
71CALIBRATION PROCEDURE- Instrument list- Description of the adjustment pointsMEASURE INSTRUMENTLock of the carriers and reference- Spectrum analyser- Oscilloscope- TesterCalibration of the audio parametersafter the FM modulation- Audio generator- FM Audio receiver- Audio spectrum analyserCOMPONENT DESCRIPTIONR161 Clipper symmetry, left channelR176 Clipper symmetry, right channelR13 Indication of the main carrier deviationR134 Indication of the secondary carrier deviationLP1, LP2, LP3, LP4 Frequency response adjustmentR41, R42, C42 Crosstalk adjustmentR103 Pilot tone level adjustmentR29 Adjustment of the main carrier deviationR104 Adjustment of the secondary carrier deviationC30, L7 Adjustment of the main carrier frequencyC102, L14 Adjustment of the secondary carrier frequencyR37 Adjustment of the main carrier output levelR76 Adjustment of the secondary carrier output levelR70 Adjustment of the video carrier (Unused)R72 Adjustment of the carriers output level
72Component layout for adjustment pointsCOMPONENT DESCRIPTIONMF1, MF2 Adjustment of the output filterJ2, J7 Audio inputs (panel)J4 IF monitor (panel)The calibration procedure of the module requires a complete structure of display board (see MTG0079)and extension module (see MTG0095) in order to perform the software selection which will be referredto later and power the module itself.
73- Menu of the Multistandard Stereo Audio Modulator ModuleVerifica sezione oscillatore a IF  collegare un analizzatore di spettro sulla monitoria del cassetto J5 econtrollare la funzionalità delle sezioni in esso presenti:qConfigure the module with IF1 and IF2 On and IF1 Level and IF2 Level at ½ of the scale andcalibrate C30 and L7 (C102 and L14) to lock the audio carriers to the intermediate frequency of the setstandard (to change the standard refer to the standard change procedure) and obtain a lock voltagebetween 2V and 3V on C4 (C113), checking that SC1 and SC2 are on Lock in the menu of the display.qConnect a spectrum analyser in tracking mode between J3 and the output of the J1 module and checkthe response of the filter calibrating MF1 and MF2 to the minimum ripple.qCalibrate the R37 trimmer to obtain on J1 the maximum level of the main carrier in output and calibrateR76 for a level of the secondary carrier -7dBc compared to the main, then calibrate R72 to obtain a levelof the main carrier of -6dBm.Verification of the audio base-band section  connect an audio source to J2 and J7 and an FMdemodulator with audio parameters measurement capability to the IF monitor of J4 and check the sections init:qConfigure the module with Mode DualSound, Audio1 Lvl 0dB, Audio2 Lvl 0dB, Zin 600W, Limiteroff, Emph present and Source front.qCalibrate R29 and R104 to obtain the correct level of audio deviation for both subcarriers.qIncrease Audio1(2) Lvl to +6dB set Limiter on, chect that the over LED lighted up and thatOverloadL(R) indicates Pres, and that the limitation circtuit acts symmetrically on both polarities of theaudio signal, using an oscilloscope on pin3 of JP1 (JP3), and retouch if needed R161 (R176), restoreAudio1(2) Lvl to 0dB and check that the LEDs become unlit and OverloadL(R) indicates Trig, ifneeded reset this indication with Reset Trig and check that it goes to Abst.qCalibrate R13 and R134 for the correct indication of the VU-METERS.qConfigure the module with Mode Mono and calibrate R103 to a 2.5kHz deviation of the pilot tone withno audio sources connected on J2 and J7.qConfigure the module with Mode Stereo and connect an audio signal to J7, calibrate R41, R42 and C42to maximise the crosstalk of the right channel over the left channel.
74Component layout SCH0210AR1 - Bot layer
75Component layout SCH0210AR1 - Top layer
76MULT. VIDEO MODULATOR MODULE MTG0072AR0DESCRIPTIONThe video signal enters the module trough a 75W BNC connection which can be selectedvia software on either the front or rear panel of the apparatus, and is conditioned to thestandard value of 1Vpp by a digital power-meter with a maximum dynamic of +/-6dB. Asample&hold system allows to set the black level independently from the video informationin order to perform clipping operations of the synchronism and luminance levels (whichcan be disabled via software).An electronic switch (selectable via software) allows to add the video pre-correction stage,made up by the synchronism regenerator and the video group delay pre-corrector. Theformer allows to regenerate a normal synchronism level for remarkably degraded videosignals, while the latter allows to correct the shape of the audio trap contained in the TVreceivers. If the synchronism regenerator is not needed, it can be disabled even if the videopre-correction stage is enabled, but it cannot be used without the latter. The processed video signal modulatesthe amplitude of the audio carrier generated by an internal local oscillator and controlled by a PLL whichlocking frequency can be selected via software in accordance with the transmission standard.The amplitude modulation of the carrier is performed by a Gilbert dell controlled in current to obtain aneffective modulation linearity. After this, there are the vestigial filter and an UF gain stage which also sums theaudio subcarriers, if any. The whole modulation system is locked to an internal 20MHz reference made up bya VCTCXO, which may in turn be locked to an external 5/10MHz reference present on the control bus, incase the precision offset support is needed.This 20MHz reference is also used in the audio modulation module in order to obtain the perfect distancebetween the audio and video carriers even without the external precision reference.TECHNICAL CHARACTERISTICSInput impedance 75W - ROS>25dBNominal level 1Vpp ±6dBInput Front and back selectable BNCGroup delay < 50nsecppFrequency response < ±0.5dBDifferential gain < ±1%Differential phase < ±2°Luminance non-linearity < ±2%k-Factor < 1%Tilt < 1%ICPM < 2°S/HUM > 48dBS/Nunwgt > 60dBS/Nwgt > 68dBClamping S/H to backporchClipper intervention On synchronism and luminanceSynchronism regenerator Effective within ±6dBGroup delay pre-corrector 8-celle, excludibleAnalog measures Synchronism andluminance levelCarrier frequency synthesis PLLFrequency reference Internal TCXOexternally lockableExternal interface Microprocessor withRS485 protocolFirmware Riconfigurabile tramite RS485
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78The module contains the following blocks:1. Input relay  chooses the video source between the BNC on the front panel of the module and the oneon the back of the apparatus; the switching is managed by the software.2. Video level regulation stage  regulates the level of the video signal by means of a digital potentiometerwhich can be programmed trough a uWIRE interface.3. Clamping stage  uses the timing information of the synchronism extraction stage (see below) to performthe sample & hold of the black level at backporch.4. Synchronism and luminance limitation  clips the synchronism and luminance levels without distortingthe crominance signal; the intervention is handled by the software and shown by a yellow LED on thefrontal panel, the intervention of the clipper, if any, is shown by two red LEDs (one for synchronism andone for luminance) on the front panel.5. Synchronism extraction stage  extracts from the video signal the synchronism timing to perform theclamping, the regeneration and the lock of the pilot tone of the stereo audio modulator (see MTG0078).6. Synchronism regeneration stage  starting from the timing information extracted by the previous stage,this processes a new synchronism pulse corrected both in level, timing and shape (rising and loweringtimes); the intervention is handled by the software and signalled by a yellow LED on the frontal panel.7. Group delay pre-corrector  performs the pre-correction of the notch filter on the audio carrier in thedemodulator of the receiver in order to equalise its group delay.8. Synchronism insertion stage  cuts the existing synchronism of the video signal and superimposes theregenerated one; due to the need of a delay in the video signal to perform the cut compared to theextraction timing of the synchronism, this stage is related to the insertion of the group delay pre-correctorwhich inserts this delay.9. Video switch  this stage chooses between the processed video signal (pre-corrected and regenerated insynchronism if needed) and the non-processed one, at this stage there is the monitor for the video baseband with 75W output with SMB connector on the frontal panel; the choice is handled by the softwareand signalled by a yellow LED on the front panel.10. Video signal level measurement  this stage detects the peak of the synchronism and luminance levelsproviding two analog voltages for the A/D conversion; the voltages will be processed by the microcontrollerof the display board (see MTG0079) to be displayed as VU-METERS.11. Synchronism level clamper  once all needed processing have been performed with the clamping atblack level, a new clamping operation at the synchronism level is made in order to perform the subsequentnegative AM modulation.12. Amplitude modulator  converts to the intermediate frequency the video signal referring to the synchronism
79peak with a modulation depth of 90% at white level.13. Vestigial SAW filter  filters the double side-band to the broadcast carrier in order to obtain a vestigialmodulation (the upper side-band is partially broadcast).14. IF Amplifier  performs the amplification after the vestigial filtering and sums the audio subcarrier(s)coming from the audio modulator module (see MTG0071/78).15. Output low pass filter  filters the presence of harmonics of the audio and video carriers.16. IF video oscillator  generates the video carrier by performing the PLL frequency synthesis; the selectablestandards and the lock indication are handled by the software.17. Riferimento a 20MHz  the frequency reference for the PLL synthesis of the video carrier is generatedby a TCXO which may be locked to a more precise 5/10MHz external reference (see MTG0076), thisreference is buffered and used as reference by the audio modulator (see MTG0071 /78) to synthesise thefrequency of the audio carrier so that there are no frequency offsets between the two carriers, even whenthere is no common external reference.18. Controller  all of the described operations are managed by a microcontroller communicating to the userinterface board (see MTG0079) by RS485 protocol; the local controller stores the status of the moduleand a reprogramming of the firmware (possible via RS485 from the display board) does not alter itscontents.CALIBRATION PROCEDURE- Instrument listMEASURE INSTRUMENTLock of the carriers and reference- Spectrum analyser- Oscilloscope- TesterCalibration of the video parametersin base bandand after the AM modulation- Video generator with VITS- AM Video receiver- Video parameters analyser
80- Description of the adjustment pointsCOMPONENT DESCRIPTIONR71 White clipper levelR92 Level of the video signal in base band (0dB on dig. pot.)R156 AM modulation depth (90%)R196 Video carrier level (-6dBm)R32, R45, R63, R81,R37, R50, R68, R86 Control of the passing band of the pre-corrector cellsR39, R54, R73, R88,R44, R59, R78, R91 Control of the group delay of the pre-corrector cellsR98 Level of the regenerated synchronismR14, R16 Timing of the cut window of the synchronismR162, R163 Shape adjustment of the synchronismC49 Control of the passing band of the pre-correctorC113 Tuning of the local oscillator of the video carrierMF1, MF3, MF5, MF8,MF2, MF4, MF6, MF9 Tuning of the group delay pre-corrector cellsMF7 Tuning of the filter on the chrome carrier of the white limiterL5 Fine tuning of the local oscillator of the video carrierJ4 IF video testpoint (50kHz)J5 UnusedJ6 VCO control voltage testpoint (7...8V)J7 TCXO testpoint (50kHz)J8 UnusedJ9 External reference testpoint (100kHz)J1 Video input (panel)J2-J13 Video link for rear inputJ11-J14 IF link for audio carrier inputJ12 IF monitor (panel)
81Component layout for adjustment points
82The calibration procedure of the module requires a complete structure of display board (seeMTG0079) and extension module (see MTG0095) in order to perform the software selection whichwill be referred to later and power the module itself.- Menu of the Multistandard Video Modulator ModuleVerification of the video base-band section  connect a video source with VITS to J1 and a videoparameter measurer to the video base-band output and check the sections included:qConfigure the module with Video Level at ½ of the scale, Clipper off, Precorr off, Sync.Restore offand Source front.qCalibrate R92 to obtain the correct levels of synchronism (Fig.1), luminance (Fig.2) and color burst(Fig.3).qIncrease Video Level to ¾ of the scale and set Clipper to on, calibrate R71 for the intervention of thewhite limitation circuit, check that the over LEDs light up and that White Clip and Sync Clip are onPres, restore Video Level to ½ of the scale and check that the LEDs become unlit and that White Clipand Sync Clip are on Trig, if needed reset this indication by means of Reset Trig anc check that WhiteClip and Sync Clip are on Abst.qConfigure the module with Precorr on and calibrate R39, R54, R73, R88, R44, R59, R78 and R91to obtain the desired group delay mask, if needed calibrate R32, R45, R63, R81, R37, R50, R68,R86 and C49 to make the passing band flat; in case this cannot be done in the base band (the videoparameters analyser has no group delay mask for the required standard) the calibration of the IF pre-corrector can be made using the AM receiver set with the trap on the audio carrier enabled, equalising thegroup delay in order to make it flat as in Fig.10 (thus automatically compensating the trap on the audiocarrier of the receiver).qConfigure the module with Sync.Restore on and calibrate R14 and R16 for the correct timing of thesynchronism pulse (Fig.5) and color burst (Fig.6) and R98 for the correct level of the synchronism(Fig.1); only if needed, calibrate R162 and R163 to equalise the rising and lowering time of the synchronismpulse.Verification of the IF oscillator section  connect a spectrum analyser on the monitor of the J12 moduleand check the sections within:
83Fig. 1 Fig. 2Fig. 3 Fig. 4Fig. 5 Fig. 6qCalibrate C113 and L5 to lock the video carrier to the intermediate frequency of the set standard (tochange the standard refer to the standard change procedure) and obtain a lock voltage between 7V and8V on J6 checking that Video is on Lock in the display menu.qIn case of problems in obtaining the lock, check that on J4, J7 and J9 there are the frequencies listed inthe table of the description of the adjustment points.Verification of the AM modulation section  connect a video source with VITS to J1, a spectrumanalyser to the monitor of the J12 module and an AM video receiver with video parameters analyser to theoutput of the J15 module, anc check the sections within:qCalibrate R196 for a level of 6dBm of the video carrier and check that the video parameters describedin the technical specifications table are obtained (see Fig.1 to Fig.14).
84Fig. 7 Fig. 8Fig. 9 Fig. 10Fig. 11 Fig. 12Fig. 13 Fig. 14
85Component layout SCH0172AR3 - Top LayerComponent layout SCH0172AR3 - Bot Layer
86MULT. IF PRECORRECTOR MODULE MTG0073AR0DESCRIPTIONThe non-linearity IF pre-correction is performed by two distinct stages which act on differentcharacteristics of the signal. The first stage works on ICPM and differential phase and gain(DGDP) of the video signal, which are small signal characteristics and thus need a pre-correction based on adapted filtering cells.The second stage works on intermodulation, which is a large signal characteristic andneeds a pre-correction based on the intervention on non-linear stages.In consideration of this, the work of the second stage is assured by am automatic gaincontrol system which comes before and after the correction cells, and which is needed tohave the system work correctly for each type of pre-correction adopted.The whole pre-correction stage can be enabled and disabled via software with a switchingsystem which prevents the overshoot at IF-level, dangerous for the final stages.TECHNICAL CHARACTERISTICSInput impedance 50W - ROS > 25dBOutput impedance 50W - ROS > 25dBNominal level -6dBmGroup delay < 10nsecppFrequency response < ±0.2dBI.C.P.M. pre-correction 3 cells: (-) (+) (level)D.P. pre-correction 3 cells: (-) (+) (level)IMD1 pre-correction 3 cells: (knee) (slope) (phase)IMD2 pre-correction 3 cells: (knee) (slope) (phase)Video signal for ICPM and DP Internal envelopment demodulatorAutomatic gain control Before and after the IMD1 cells, 2Pre-correction Excludible via softwarePre-corrector intervention Can be enabled even when powered, without overshootAnalog measures ---
87
88The module contains the following blocks:1. Input amplifier  de-couples the input of the module from the internal pre-correction sections.2. Input/output relay  inserts or excludes the pre-corrector from the IF chain with the timing needed to avoidpower overshoot due to the internal AGC stages; the switch is handled by the software and signalled by ayellow LED on the frontal panel.3. Envelopment demodulation stage  extracts the video information from the AM modulation in order toprocess the interventions on the pre-correction of ICPM and DP.4. Conditioning stages of the video signal (2)  these use the information extracted by the demodulator andprocess it by inserting some deformation stages of the video signal which parameters (lower cut, upper cut andlevel) depend on the controls on the frontal panel.5. Equalisation cell  equalises the passing band of the IF pre-corrector by inserting a band-pass filter cellbetween the ICPM (set on the video carrier) and DP (set on the audio carrier) pre-correction cells.6. ICPM pre-correction cell  performs the intervention set by the ICPM conditioning stage on the band-passfilter cell set on the video carrier.7. DP pre-correction cell  performs the intervention set by the DP conditioning stage on the band-pass filter cellset on the audio carrier.8. Automatic gain control stage (in)  performs the gain control on the IF signal in order to have the IMD pre-correction cells always work on the optimal point.9. Intermodulation pre-correction cells (2)  pre-correct the three-tones intermodulation by inserting twonon-linearity stages which parameters (knee, slope and phase) depend on the controls on the frontal panel.10. Automatic gain control stage (out)  performs the gain control on the IF signal in order to obtain an outputsignal which level does not depend on the inserted pre-correction.11. Output low-pass filter  filters the presence of harmonics inserted by the linearity pre-corrector.CALIBRATION PROCEDUE- List of instrumentsMEASURE INSTRUMENTCalibration of the pre-correction cellsand envelopment demodulator- Spectrum analyser with tracking- OscilloscopeCalibration of the video parametersafter the pre-correction- Video generator with VITS- AM Video receiver- Video parameters analyser
89- Description of the adjustment pointsCOMPONENT DESCRIPTIONR12 IF level without pre-correction (-6dBm)R123 IF level before the IMD pre-corrector (0dBm)R126 IF level after the IMD pre-corrector (-6dBm)C57, L11 Band-pass filter on the video carrier of the envelopment demodulatorC14, L10 Notch filter on the audio carrier of the envelopment demodulatorC23, L9 Tuning of the equalisation band-pass filterR7, C4 Merit and gain factor of the equalisation band-pass filterC20, L7 Tuning of the ICPM band-pass filterR5, C3 Merit and gain factor of the ICPM band-pass filterC17, L5 Tuning of the DP band-pass filterR3, C1 Merit and gain factor of the DP band-pass filterL1, L2, L3 Need no calibrationR187, R188, R189 Calibration of the ICPM parametersR190, R191, R192 Calibration of the DP parametersR193, R194, R195 Calibration of the IMD1 parametersR196, R197, R198 Calibration of the IMD2 parametersJP1, JP2 Jumpers to calibrate the IF filter concerning the ICPM and DP cellsJ2 IF input of the filter concerning the ICPM and DP cellsJP3, JP4, JP5 Jumpers to esclude the cells of the ICPM and DP IF filtersJ1, J9 IF link (J1 is also the output of the ICPM and DP filter)JP10, JP11 Configuration jumpers of the IMD cells (do not use)J4, J11 IF linkJ8 IF moni tor (panel)JP6, JP9 Configuration jumpers of the intervention of the DP pre-correctionJP7, JP8 Configuration jumpers of the intervention of the ICPM pre-correction
90Component layout for adjustment points
91The calibration procedure of the module requires a complete structure of display board (see MTG0079)and extension module (see MTG0095) in order to perform the software selection which will be referredto later and power the module itself. Besides a video modulator module (see MTG0072) and an audiomodulator module (see MTG0071/78) already calibrated are needed to calibrate, if neededm theenvelopment demodulator (only for the first calibration or to change the standard).- Menu of the Multistandard IF Precorrector ModuleVerification of the ICPM and DP pre-correction section  connect a spectrum analyser with trackingbetween J2 and J1 and check the sections therein:qCalibrate C20 and L7 to tune the cell of I.C.P.M. to the frequency of the video carrier summing about750kHz (Fig.1) with JP4 on and JP3 and JP5 off.qCalibrate C17 and L5 to tune the cell of D.P. to the frequency of the audio carrier subtracting about750kHz (Fig.2) with JP3 on and JP4 and JP5 off.qCalibrate C23, L9 to tune the equalisation cell to the middle of the intermediate frequency (Fig.3) withJP5 on and JP3 and JP4 off.qSet JP3, JP4 and JP5 on and check the response of the filter curve (Fig.4) to the desired passing band,if needed retouch R3, R5 and R7 to correct the ripple in band and C1, C3 and C4 to equalise the groupdelay of the filter obtaining a frequency response as in Fig.5.Verification of the envelopment demodulator section  connect the module to the frame provided withvideo modulator by means of the extension board and check the sections therein:qCalibrate C57 and L11 to obtain the best demodulation of the video signal by connecting an oscilloscopeto C44 (only if changing the IF standard).qCalibrate C14 and L10 to obtain the best attenuation of the audio signal superimposed to the video signalconnecting an oscilloscope to C44 (only if changing the IF standard and with at least one audio module inthe frame).Verification of the IMD1, 2 pre-correction sections  connect a spectrum analyser with tracking betweenJ9 and J10 and check the sections therein:
92Fig. 1 Fig. 2Fig. 3 Fig. 4Fig. 5 Fig. 6qConfigure the module with Prec enabled.qCalibrate R123 to an IF level of 0dBm on R178 and calibrate R126 to an IF level of -6dBm on J10 withthe tracking on -6dBm.qCheck that the passing band of the section is similar as the one in Fig.6 and able to cover the whole IFband from 30MHz to 50MHz.Verification of the module without pre-correction  connect a spectrum analyser with tracking betweenJ3 and J10 and check the sections therein:qConfigure the module with Prec disabled.qCalibrate R12 to an IF level of -6dBm on J10 with the tracking on -6dBm.qCheck that the passing band of the section is flat within 0.2dB on the whole IF from 30MHz to 50MHz.
93The testing procedure of the linearity pre-corrector is the consequence of a series of subsequentinterventions on the pre-corrector cells in order to achieve a good compromise of the video parametersof the amplifier at the working power.A calibration technique for the cells allowing to satisfy these requirements is proposed below; thechoice of the good compromise on the video parameters is anyway entrusted to the skill of the tester.IMD1, 2 pre-correction - the intermodulation pre-correction inserts distortions in the negative Am modulationlinear characteristic of the video signal in order to compensate the distortions due to the power amplifier.These are characterised by three parameters: Knee, Slope and Phase, and introduce some deviations fromthe input/output linear characteristic of the pre-corrector.For a more complete possibility of shaping the non-linearity characteristic, there are two pre-correction cellsin two particular regions of the characteristic: 50% APL (cell 1) and 100% APL (cell 2).The suggested procedure to compensate the characteristic of the final power stage is to start positioning cell1 (by acting on the K and S trimmers) in order to find a minimum point for the intermodulation, then positioncell 2; retouch the P trimmer if needed to refine the pre-correction.Usually cell 1 only is needed to pre-correct A-class final stages, while for AB-class ones both cells areneeded.In order to exclude one of the cells (or both at the beginning of the pre-correction procedure) it only takesdecreasing the K, S and P trimmers to the minimum.Perform the pre-correction procedure for the intermodulation with the red bar video signal and repeat it forthe other colours if needed, refining the pre-correction.ICPM pre-correction  a catalogue of the different kinds of pre-correction which can be introduced on theICPM parameter is given below. Once the measure has been taken, the situation which better approximates50%APL 100%APL IN OUT AM-AM 50%APL 100%APL IN OUT AM-PM
94the compensation has to be found, then the figure reproducing the measure in a specular way is to beconsidered.In the catalogue there are also the positions of the trimmers and the jumpers to obtain all proposedconfigurations, of course intermediate solutions are possible and the intensity of all solutions may be scaled bymeans of the level trimmer which is considered to be at the maximum intervention in the catalogue.DP pre-correction  a catalogue of the different kinds of pre-correction which can be introduced on the DPparameter is given below. Once the measure has been taken, the situation which better approximates thecompensation has to be found, then the figure reproducing the measure in a specular way is to be considered.In the catalogue there are also the positions of the trimmers and the jumpers to obtain all proposedconfigurations, of course intermediate solutions are possible and the intensity of all solutions may be scaled bymeans of the level trimmer which is considered to be at the maximum intervention in the catalogue.
95 - I.C.P.M. Pre-correction catalogue with: JP7 ®1-2; JP8 ® 1-2
96- I.C.P.M. Pre-correction catalogue with: JP7 ®2-3; JP8 ® 1-2
97- I.C.P.M. Pre-correction catalogue with: JP7 ®1-2; JP8 ® 2-3
98- D.P. Pre-correction catalogue with: JP6 ®1-2; JP9 ® 1-2
99- D.P. Pre-correction catalogue with: JP6 ®2-3; JP9 ® 1-2
100- D.P. Pre-correction catalogue with: JP6 ®1-2; JP9 ® 2-3
101Component layout SCH0209AR1

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