ADVANCED TV LINE Model AT7400 400W ATSC UHF Transmitter OWNERS MANUAL Linear Industries Incorporation www.linear-tv.com Made in USA AT7400 Owner Manual Rev. 2.
AT7400 400W ATSC DTV TRANSMITTER ADVANCED TV LINE Owner Manual Table of Contents AT7400 Section 1: Technical Specifications Typical Final Test Report Section 2: Master Control Unit Section 3: Exciter Drawer Section 4: Intermediate Directional Coupler Section 5: 220W UHF Power Amplifier Section 6: Output Directional Coupler, and Filtering Section 7: Energy Distribution and Control Annex A: Schematics Diagrams Owner Manual Rev. 2.
User Notices and WARNINGS USER NOTICES IT IS VERY IMPORTANT TO READ THE FOLLOWING MANUAL SECTIONS PRIOR TO OPERATION OF THIS TRANSMITTER! Notice 1 The transmitter main operating voltage setting is marked on the rear of the AT7250 chassis. Notice 2 The transmitter operating frequency is set from the factory. Notice 3 For adjusting the RF output power setting a qualified technician should always employ the use of an RF Wattmeter and a calibrated dummy load.
WARNING! THE VOLTAGES AND CURRENTS IN THIS EQUIPMENT ARE DANGEROUS. PERSONEL MUST, AT ALL TIMES, OBSERVE SAFETY WARNINGS, INSTRUCTIONS, AND ANY REGULATIONS. THIS OWNER’S MANUAL IS INTENDED AS A GENERAL GUIDE FOR TRAINED AND QUALIFIED PERSONNEL WHO ARE AWARE OF THE DANGERS THAT ARE INHERENT IN THE HANDLING AND OPERATION OF POTENTIALLY HAZARDOUS ELECTRICAL AND ELECTRONIC CIRCUITS.
Returns and Exchanges Equipment (Damaged or undamaged) should not be returned unless written approval and a Merchandise Return Authorization (MRA Number) is received from your Linear Sales representative or Linear Customer Service. Special shipping instruction will be provided which will assure proper handling. The circumstances and reasons for the return must be included in the request for return. Equipment that is special or “custom” ordered may be not returnable.
Section 1 – AT7400 Technical Specifications 1. Introduction The AT7400 is a 400W UHF ATSC/8VSB transmitter assembled and tested in United States by LINEAR INDUSTRIES INC. (www.linear-tv.com). Fig1.1: AT7400 Front View, cabinet wheels are optional. AT7400 Owner Manual Rev. 2.
2. AT7400 RF line Up 3. AT7400 Cabinet Air Flux: 0.25m3/sec. - 21ft3/sec. Air Outlet Cold Air Inlet Fig. 1.4: Air flux path at AT4700 cabinet, (lateral view). Darker area denotes the internal heat source, or the RF drawers, (1) Exciter and (2) PA’s. AT7400 Owner Manual Rev. 2.
4. AT7400 – 400W UHF ATSC/8VSB Transmitter - Technical Specifications Electrical Main Consumption PFC Signal Input Transport Stream Input Input Data Rate External Reference Signal Input Connector Reference Input Connector RF RF Output Power Modulation Mode IF Channel Bandwidth Test Signal Frequency Range Frequency Step Symbol Rate Digital/Analog Converter All –Digital Linear.
5. AT4700 Available Models and Options Models A B C Options: 01 02 03 04 05 Mono-phase; 220Vac. 3-phase; 220Vac – 380Vac; 3 wires. 3-phase; 220Vac – 380Vac; 4 wires. Integrated GPS receiver Adaptive digital pre-correction Dual Exciter Analog Transmission Mode Cabinet 4 wheels 6. AT7400 Typical Test Report 6.1.Out of Channel Emissions AT7400 Owner Manual Rev. 2.
6.2.Frequency Response and Group Delay 6.3.Carrier Phase Noise AT7400 Owner Manual Rev. 2.
6.4.Digital Modulation Error Rate AT7400 Owner Manual Rev. 2.
6.5.Conducted Spurious Emissions AT7400 Owner Manual Rev. 2.
Section 2 – Master Control Unit Module 4459 1. General Description The main control unit, MCU, is the logical master unit acting all over the transmitter operational functions. The MCU is constantly connected and exchanging information via RS485 with the UHF power amplifiers units and the UHF exciter unit. External keyboard allows local changing on parameters and monitoring, displayed on a LCD screen.
2.6.Module 4459 Block Diagram Fig.2.2: – Module 4459 block diagram and PCBs displacement. AT7400 Owner Manual Rev. 2.
Owner Manual Rev. 2.0 – October 2006-10-23 RS2 32 1 RS48 5 .. 6 CON-7 DS2 29 6 . 1 CON- 8 MC9S 12A128B 9 1 CI -6 CON-12 3 1 J4 J5 CON-6 8 VM A B GND 1 1 6M Hz X TAL1 1 ( BL) RS4 85 A ? PI N 8 – P3 ( GY) RS48 5 B ? PIN 7 – P3 PI N 1 – CON 1 – KEYBOARD – CIM 31 12 PI N 2 – CON 1 – KEYBOIARD – CIM 31 12 PI N 3 – CON 1 – KEYBOARD – CIM 31 12 PIN 4 – CO N 1 – KEYBOA RD – CI M31 12 CON-5 8 BDM I N ( BK) ? ( BL) ? ( RD) ? (B R) ? CON- 4 1 CON-9 DS22 9 .
Fig.2.4: – Module 4459, CIM 3297 the transmitter main microcontroller. 2.7.1. Digital Control o The integrated circuit CI-4 (A128) is a 16 bit microcontroller, programmed on assembler language. This integrated circuit controls this module, 4459, and also the entire transmitter. This IC carries a controlled software version, and is programmed on factory.
2.7.2. Analog Readings Information on analog format is available at the connectors P1 and P2 on the module 4459’s panel, which are routed to CON-9 at the PCB CIM3297. On P1-P2 connectors are available the following analog reading from external measurements: Fig. 2.5: - Module 4459 external connections and internal connections view. AT7400 Owner Manual Rev. 2.
2.7.2.1 Direct RF power, and reverse RF power. From the RF output directional coupler, module 4429. 2.7.2.2 Direct RF driver power, and reverse RF driver power. From the RF intermediate directional coupler, module 4429. 2.7.2.3 +8V, from the DC/DC converter; module 4147. 2.7.2.4 +15V, from the DC/DC converter; module 4147. 2.7.2.5 The 12V/7Ah battery voltage. From the connector CON-9 these readings feed the microcontroller CI-4, from where those are digitalized and processed.
2.7.4. RS485 Communication bus On the PCB CIM3297, pin 1 and pin 2, at the CON-12 perform the RS485 communication link among the MCU, the UHF exciter driver drawer and the UHF power amplifier drawers. 2.7.5. Interface SNMP The interface SNMP is the PCB CIM3453. The connectors CON-4 and CON-10 located at the PCB CIM 3297 links the 2 PCBs. Fig. 2.6: - Module 4459 SNPM interface, PCB CIM3453, internal and external view. AT7400 Owner Manual Rev. 2.
2.7.6. Displaying the Exciter and Power Amplifier Drawers Alarms Each drawer has its own local control units. The local processed data is link to the MCU via RS485 protocol. The MCU unit analyze, command actions and display at the LCD, the overall system status. Alarms from the drawers, are displayed as drawers alarms, followed by one of each signs “!”, or “#”.
2.7.9. Module 4459 Internal Wiring Fig. 29: - Module 4459 wiring diagram. 2.7.10. Module 4459 Schematic Diagrams: SEE ANNEX A 2.7.10.1 - PCB CIM3297 2.7.10.2 - PCB CIM3112 2.7.10.3 - PCB CIM3108 2.7.10.4 - PCB CIM3453 AT7400 Owner Manual Rev. 2.
Section 3 – 20W UHF ATSC Exciter Unit/Drawer GAV4452 1.General Description The 20W UHF ATSC exciter drawer performs several important functions, as follows: a. The 8VSB modulation. Incoming SMPTE310 data stream, over an IF carrier, 21.52MHz. b. Insert the pre-distortion function over the modulated IF signal. Fig.3.1: Top GAV4452 front view, bottom GAV4452 rear view. c. Up-convert the IF signal on UHF ATSC broadcast channel. d. The output RF power control. e.
The modules assembled into the GAV4452 are: x x x x x x 01 Module 4454 - 8VSB Modulator and MASTER Clock Generator 01 Module 4453 - IF/UHF Up-Converter 01 Module 4466 - DDS 01 Module 4464 - 20W UHF / ATSC 01 Module 4456 - Power Supply 01 Subordinate Control Unit (SCU) – CIM3297 Fig.3.2: GAV4452 modules displacement, top view. AT7400 Owner Manual Rev. 2.
P HA S E 1 Owner Manual Rev. 2.0 – October 2006-10-23 • PHASE 1 / PHASE 2 :1 2 0V AC +32V 20 8V AC + 15 V + 5V +2 .5V MO DULE 4470 PH A S E 2 OR N E UT RA L ON/ OFF S WI TC H F AN 1 4 3 +32V 20 8V MO NOPHASIC AND 36 0 VTRIPHASIC EQUIPAMENTS: • PHASE 1: 20 8 V AC •NE UTRAL 20 8V BIPHASIC AND 2 08 VTRIPHASIC EQUIPAMENTS: FAN 2 1 0 AFUSE 2 1 5 6 4 2 3 +1 .
3.GAV4452 - Module 4454 – 8VSB Modulators and Master Clock 3.1. General Functional Description The module 4454 can be break down in 2 printed circuit boards. These boards are physically located as the figure below: CON-7 (WH) GROUND ? CON-5 – CIM3458 – MOD.4470 – VOLTAGE REGULATORS (BR) +5V ? CON-2 – CIM3459 – MOD. 4456 – POWER SUPPLY (BK) -15V ? CON-3 – CIM3461 – MOD. 4456 – POWER SUPPLY (BL) +15V ? CON-2 – CIM3461 – MOD. 4456 – POWER SUPPLY (OR) +3.3V ? CON-8 – CIM3458 – MOD.
CIP8357 SMPTE 310 External Reference 10MHz 8VSB Modulator & pre-distortion Master Clock 172.16MHz CIP8358 Sub-module 4454 CIP8355 I I' Q Q' Mixer & ALC RF UHF -2.3dBm PLL + DDS 4 x VCO/off set CIP8356 Sub-module 4453 Fig.3.4: Module 4454- 8VSB Modulation and IF/UHF up-conversion structure 3.1.1. Module 4454 - PCB CIM3444: 8VSB Modulator/Pre-Corrector The PCB CIM3444, is part of the Module 4454.
3.1.1.1 PCB CIM3444 – General Functional Description The ADVANCE TV series is designed to receive as input signal, programming stream, standard SMPTE310M,with 19.39M bps, amplitude of 800 mVpp, @75ȍ. The input BNC connector is located on the top cover of the transmitter rack. First the circuit to recover the clock rate used to perform the protocol interface.
3.1.1.1.7. Pilot Insertion This part of the circuit adds a small DC level into the carrier to allow a safer and robust reception of the signal. This DC level is equivalent to 1.25 CU (Constellation Units). The entire modulation process is digital. This process includes the FIR filters, and do not uses SAW filters to create the VSB band. Digital modulation increase the quality of the modulated signal measured via a proportional increase of the MER, (Modulation Error Rate).
3.1.3. PCB CIM3445 – Master Clock - Block Diagram 3.1.4. PCB CIM3445 – General Functional Description The 172.16MHz frequency is synthesized via a PLL, a VCO and a DDS circuit. The 10MHz reference is one out of the two inputs of the phase comparator. This signal comes to CIP8358 via a SMB connector, CON-2. The second one is also a 10MHz generated by the DDS circuit out from the free running 172.16MHz oscillator.
3.2.1. Module 4453 - External Connections CON-2 (WH) GROUND ? CON- 5 – CIM345 8 – MOD.4470 – VOLTAGE REGUL ATORS (OR) +3.3V ? CON- 8– CIM345 8 – MOD.4470 – VOLTAGE REGUL ATORS (BK) -15V ? CON-3 – CIM3461 – MOD. 445 6 – PO WER SUPPLY (BL) +15V ? CON- 2 – CIM3461 – MOD. 4456 – POWER SUPPL Y (VM) +32 V ? CON- 10 – CIM34 47 – MOD.
3.2.2. PCB CIM3443 – Local Oscillator The local oscillator is designed based on a PLL circuit. This oscillator is able to synthesize frequencies within the band from 450MHz up to 900MHz. To guarantee a high quality signal generation out from the local oscillator, 4 VCO’s (voltage controlled oscillator) were implemented with a shift frequency range of 125MHz each. Just one VCO works at the time to avoid interferences. On this arrangement, a 102dBc@20Hz phase noise is achieved.
3.3.1. PCB CIM3442 – UHF Mixer – Block Diagram AT7400 Owner Manual Rev. 2.
3.3.2. PCB CIM3442 – UHF Mixer – Test Points Diagram AT7400 Owner Manual Rev. 2.
3.3.3. PCB CIM3442 – UHF Mixer – Adjustment Procedures The mixer-ALC circuitries have 2 types of adjustments. The first one is a DC level that polarizes each branch of the input of the complex mixer. Each one of the DC levels must be adjusted seeking for the max rejection on the un-desired vestigial side band, in conjunction with the LO rejection as well. The level adjustments are performed by the trim pots: TPO-1, TPO-2, TPO-3, and TPO-4. Voltage range of +1.4V to +1.
3.5. Module 4466 – External Connections AT7400 Owner Manual Rev. 2.
3.6. Module 4464 – 20W UHF ATSC Power Amplifier The RF/UHF signal, already set to the assigned channel, is than power amplified up to 20W. The RF amplifier is type class AB. LDMOS transistors are also used on this amplification stage. Fig.:3.2; illustrates the RF chain of the module 4464. Module 4455: 20W power amplifier Printed Circuit Board CIM 3440 BLF861A Printed Circuit Board CIM 3446 H RF UHF -2.3dBm SG9289 H BLF861A BLF1822 RF UHF 0.
3.1.3.1 General Functional Description The PCB CIM 3390 delivers is the output nominal ATSC UHF 20W output power for the module 4455 – intermediate directional coupler.
3.9.1. Module 4464 – Technical Specifications CHARACTERISTIC SPECIFICATION SMPTE310M INPUT FREQUENCY 470 - 862MHz IMPEDANCE 75 Ohms CONNECTOR BNC FEMALE RETURN LOSS ³ 22dB RF OUTPUT GAIN FROM 45 TO 48dB ATSC AVERAGE POWER UNTIL 20W HARMONICS £ -60dB SPURIOUS EMISSION < -54dB INTERMODULATION < -52dB CONECTOR N FEMALE GENERAL AT7400 POWER SUPPLY +32V / +12V / +5V CONSUMPTION 14A (AB CLASS) Owner Manual Rev. 2.
3.9.2. Module 4464 – PCB CIM3446 – 32dB Gain Driver 0.5w Amplifier The PCB CIM 3446 is the driver amplifier for the 20W final amplifier. This circuit is 2 parallels cells, type class A polarization, 90 degree out of phase, able to delivery up to 1W of power usable for DTV/ATSC standard over the 470MHz – 806MHz UHF band. Fig.3.9: Module 4464 – CIM3446 – block diagram Each amplification cell is composed first by a BJT transistor followed by a LDMOS transistor.
3.9.3. Module 4464 – CIM 3446 – Technical Specifications AT7400 Owner Manual Rev. 2.
3.9.4. Module 4464 – PCB 3446 – Adjustment Procedures The PCB CIM3446 can be adjusted either locally, meaning inside of the equipment, (recommended for simplicity) or outside of the equipment. On either situation, one MUST always use a 50ȍ load connected at the RF output.
3.9.4.1.1. Transistor T2 1 – Turn TPO-1’s knob all way counter clock wise, no T2-ID will be present. 2 – Connect the multi-meter over the terminals of R13, the T2-drain resistor. 3 – Slowly start to turn TPO-1 knob clock wise up to the point that T2 starts to conduct, meaning few mili-volts will be read at the multi-meter. Continue it up to a 3Vdc reading be shown over R13. 3.9.4.1.2. Transistor T4 1 – Turn TPO-2’s knob all way counter clock wise, no T4-ID will be present.
AT7400 +15V +1 2V +12 V +12 V +32V (VA) Owner Manual Rev. 2.
3.9.5.1 RF Hybrid Input This hybrid equally splits the incoming RF signal, keeping the input impedance at 50ȍ level on an eventual amplification cell malfunction. This hybrid is built out of 2 coupled transmission lines. In one end of the first transmission line is connected the RF input signal, and on the other end a 50ȍ/10W (R1 parallel with R2) resistive termination. On the ends of the second transmission line the coupled RF signal feeds the 2 amplification cells. Fig.3.
3.9.5.3 UHF 12.5W Driver Amplifier – Cell B, Transistor 2 On this cell, the trim-pot TPO-3 at the same time adjusts the VGS2 voltage for T2, and the drained current ID. The trimmers C35, C39 and C43, tunes and adjusts the input impedance. A combination among the trimmers’ physical position and transmission lines’ length determines the bandwidth behavior. At the input, the capacitor C31 is a input DC de-coupling, and at the output C56 as well. 3.9.5.4 Output Combiner The 12.
3.9.6. Module 4464 – PCB CIM3440 – Technical Specifications FEATURE SPECIFICATION INPUT FREQUENCY 470 - 862MHz IMPEDANCE 50 Ohms RETURN LOSS ³ 22dB OUTPUT GAIN 13 TO 16dB RF POWER UNTIL 20WRMS HARMONICS £ -60dB SPURIOUS EMISSION < -54dB INTERMODULATION < -46dB IMPEDANCE 50 Ohms GENERAL VOLTAGE SUPPLY +32V CONSUMPTION 12A (AB CLASS) 3.9.7.
3.9.7.1 Drain Current ID, Adjustment Turn the unit ON and wait 3 minutes for thermal stability. Use a good quality multi-meter able to read mVdc, avoid to used auto-range multi-meters. 3.9.7.1.1. Transistor T1 1 - Set the trim-pot TPO-1 all way counterclockwise. On this condition no current flow over the transistor. 2 – Measure the voltage drop over R9. Set the multi-meter for 100mVdc full scale. 3 – Slowly start to turn the TPO-1 trim-pot clockwise up to the point one read 60mVdc over R9. 3.9.7.1.2.
NETWORK ANALYZER RFIN RFOUT 30dB / 50W ATTENUATOR T1 T3 . CI-2 HC-1 HC -1 . .. --C4I4 . .. CI-1 R9 +32V / 2A T4 RFIN CC4 42 22 C 4 C3 9 C3 9 ID1 ID2 TEMP R10 +32V CON-2 +32V / 2A RFOUT BLF861A BL F8 61 A C3 5 CI-5 CI-8 TPO-2 TPO-2 T2 VG S ADJ CON-2 +32V . CI-7 S1 S1 CI-3 -CON 3 3 CON C1 C1 C1 33 C9 TPO-1 VG S ADJ T1 BLF8 6 1A C5 C5 R11 T2 MODULE 4464 Fig. 3.
Fig. 3.13: Module 4456 – 60A multiple power supply The module 4456 generates the following voltage values for this drawer internal use only: Voltage +32V Fixed +32V ON/OFF according to command. +15V Direct +15V -15V +5V +2.5V Current 2A 15A 1A 2A 200 mA 5A 5A Table 2 - Module 4456: Listing of Voltage and current, per each power supply. The multiple power supply module 4456 is composed by the following PCB’s: AT7400 Owner Manual Rev. 2.
Fig. 3.13: Module 4456 - Circuit functions: electrical schematic diagram, (CIM), and printed circuit board, (CIP). AT7400 Owner Manual Rev. 2.
3.10.1. AT7400 Module 4456 – Block Diagram Owner Manual Rev. 2.
