INSTRUCTION MANUAL DT830A 300-WATT DIGITAL UHF TRANSMITTER AXCERA, LLC 103 FREEDOM DRIVE, P.O. Box 525 LAWRENCE, PA 15055-0525 USA (724) 873-8100 • FAX (724) 873-8105 www.axcera.com • info@axcera.
300-Watt Digital UHF Transmitter Table of Contents TABLE OF CONTENTS CHAPTER 1 INTRODUCTION 1.1 1.2 1.3 1.4 1.5 1.6 Manual Overview...................................................................................1-1 Assembly Designation Numbers ..............................................................1-1 Safety ..................................................................................................1-1 Maintenance ...........................................................................
00-Watt Digital UHF Transmitter Table of Contents TABLE OF CONTENTS (continued) 4.2 8-VSB Digital Modulator ....................................................................... 4-20 4.2.1 Vector Modulator Board .............................................................. 4-20 4.2.2 Switch Board ............................................................................. 4-21 4.2.3 Local Oscillator Board ................................................................. 4-21 4.2.4 LED Board .........
300-Watt Digital UHF Transmitter Table of Contents TABLE OF CONTENTS (continued) 5.3 8-VSB Modulator....................................................................................5-8 5.3.1 VSB Modulator Interface Board ......................................................5-9 5.3.2 VSB Symbol Generator Board ........................................................5-9 5.3.3 VSB Filter Board......................................................................... 5-11 5.3.4 Switch Board ...............
300-Watt Digital UHF Transmitter Table of Contents LIST OF FIGURES 2-1 Remote Interface Panel...................................................................2-8 3-1 1 kW Minimum Ventilation Configuration ..........................................3-4 5-1 Typical Digital Spectrum .................................................................5-3 DT830A, Rev.
300-Watt Digital UHF Transmitter Table of Contents LIST OF TABLES 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 2-14 2-15 DT830A Major Assemblies and Trays ................................................2-1 Digital Modulator Display ................................................................2-3 Digital Modulator Control Pushbuttons ..............................................2-4 Digital Modulator Status Indicators...................................................
300-Watt UHF Digital Transmitter Chapter 1, Introduction Chapter 1 Introduction This manual explains the installation, setup, alignment, and maintenance procedures for the DT830A 300-watt digital UHF transmitter. It is important that you read all of the instructions, especially the safety information in this chapter, before you begin to install or operate the unit. associated part number(s) and the relevant appendices.
300-Watt UHF Digital Transmitter Chapter 1, Introduction thermal shutdown or the premature failure of the affected trays. Ventilation – Openings in the cabinets and tray front panels are provided for ventilation. To ensure reliable operation, and to protect the unit from overheating, these openings must not be blocked. When the front panels of the trays become dust covered, the top covers should be removed and any accumulated foreign material should be removed.
300-Watt UHF Digital Transmitter Chapter 1, Introduction Note: To prevent damage to the product during shipping, Axcera will supply a shipping container to the customer at no cost. under normal use and service for a period of one (1) year from the date of shipment from Axcera's plant, when operated in accordance with Axcera's operating instructions. This warranty shall not apply to tubes, fuses, batteries, or bulbs. When equipment is sent to the field on loan, an MRA# is included with the unit.
300-Watt Digital UHF Transmitter Chapter 2, System Description Chapter 2 System Description The DT830A is a complete 300-watt (average) UHF solid-state digital television transmitter that operates at a nominal average output power of 300 watts. 2.1 System Overview The DT830A consists of the assemblies and trays listed in Table 2-1. Table 2-1.
300-Watt Digital UHF Transmitter Chapter 2, System Description The (A14-A1) 10-MHz reference generator board (1519-1126) is located in (A10) the 10-MHz reference kit (12861108). The board contains a highstability crystal oscillator that provides a 10-MHz output that is used as reference frequency for the transmitter. The board is mounted within an enclosed assembly that helps to maintain the operating temperature of the oscillator board. to approximately 300 watts.
300-Watt Digital UHF Transmitter Chapter 2, System Description of the (A2) AC distribution panel. The AC distribution panel contains four circuit breakers, six in the upgradeable version, which supply the AC to the rest of the transmitter. 2.2 Control and Status Control and status indications of the transmitter are provided by the meters and LED indicators on the front panel of the UHF exciter.
300-Watt Digital UHF Transmitter Chapter 2, System Description Table 2-3. Digital Modulator Control Pushbuttons PUSHBUTTON Menu Up Arrow (↑) Down Arrow (↓) FUNCTION Controls which menu is displayed on the LCD readout Moves the active line up one position on the LCD display Moves the active line down one position on the LCD display There are four front panel status indicator LEDs. Table 2-4.
300-Watt Digital UHF Transmitter METER % Exciter (0-120) % Output power (0-120) % Reflected (0-120) Chapter 2, System Description FUNCTION Reads the % Exciter Output Power level needed to attain 100% output of the transmitter on the top scale Reads the % Output Power of the transmitter on the top scale Reads the % Reflected Output Power, <5%, on the top scale Table 2-7.
300-Watt Digital UHF Transmitter Chapter 2, System Description Table 2-9. UHF Exciter Tray Samples SAMPLE f(s) Exciter O/P Transmitter O/P DESCRIPTION A sample of the channel oscillator output, taken from the sample jack of the channel oscillator assembly An output power sample of the exciter taken from the UHF upconverter board A forward power sample of the transmitter taken from the visual/aural metering board before the signal reaches the bandpass filter 2.2.
300-Watt Digital UHF Transmitter Chapter 2, System Description Table 2-11. UHF Amplifier Tray Status Indicators INDICATOR Enable (DS4 green) Overdrive (DS2 red) VSWR cutback (DS1 red) Overtemp (DS3 red) Input fault (DS5 red) FUNCTION Indicates that an Enable, Operate, command is applied to the UHF amplifier tray from the UHF exciter tray Indicates that the level of the drive is too high. The protection circuit will limit the drive to the set threshold.
300-Watt Digital UHF Transmitter Chapter 2, System Description Figure 2-1. Remote Interface Panel The remote connections shown in Tables 2-14 and 2-15 are made if (A12) the input and remote interface assembly is present in the system. The remote DT830A, Rev. 1 connections are made to jacks J9 and J10 on the assembly. Refer to the interconnect drawing (1127833) for the proper pin remote connections.
300-Watt Digital UHF Transmitter Chapter 2, System Description Table 2-14. Remote Interface Panel Connections FUNCTION Transmitter Enable Interlock Transmitter Enable Interlock Rtn REMOTE JACK/PIN NUMBER J9-21 J9-22 INTERFACE TYPE J9-21 and 22 must be jumpered for normal operation; (1176-1038) jumper jack is used.
300-Watt Digital UHF Transmitter FUNCTION Chapter 2, System Description REMOTE JACK/PIN NUMBER Remote Metering INTERFACE TYPE Digital Output Power Digital Output Power Rtn J9-1 J9-2 1V full scale at 1kΩ source resistance Reflected Power Reflected Power Rtn J9-5 J9-6 1V full scale at 1kΩ source resistance Exciter Output Power Exciter Output Power Rtn J9-7 J9-8 1V full scale at 1kΩ source resistance Table 2-15.
300-Watt Digital UHF Transmitter Chapter 3, Installation and Setup Procedures Chapter 3 Installation and Setup Procedures There are special considerations that need to be taken into account before the DT830A can be installed. For example, if the installation is completed during cool weather, a heat-related problem may not surface for many months, suddenly appearing during the heat of summer. This section provides planning information for the installation and set up of the transmitter. room.
300-Watt Digital UHF Transmitter Chapter 3, Installation and Setup Procedures Ventilation will work quite well if the ambient air temperature is below 100° F, or about 38° C, and the humidity is be kept at a reasonable level. In addition, the air stream must be adequately filtered to ensure that no airborne particulate of any kind will be carried into the transmitter.
300-Watt Digital UHF Transmitter Chapter 3, Installation and Setup Procedures filter. This is not a conservative number but a never-exceed number. In a dusty or remote location, this number should be reduced to 150 CFM. 7. The inlet and outlet(s) must have automatic dampers that close any time the ventilation blower is off. 8. In those cases in which transmitters are regularly off for a portion of each day, a temperature-differential sensor that controls a small heater must be installed.
300-Watt Digital UHF Transmitter Chapter 3, Installation and Setup Procedures Figure 3-1. 1 kW Minimum Ventilation Configuration 3.2 Unpacking the Cabinets from the skid. Remove the plastic wrap and foam protection from around the cabinet. Do not remove any labeling or tags from any cables or connectors; these are identification markers that make assembly of the transmitter much easier.
300-Watt Digital UHF Transmitter Chapter 3, Installation and Setup Procedures Caution: Each UHF amplifier tray has a hardline coaxial cable connected to the bottom panel. The tray will not slide out unless this cable is first removed. To pull the tray out for test purposes, use the extender coaxial cable included in the installation material kit for connections from the tray to the output cable. the AC distribution panel near the rear door of the transmitter.
300-Watt Digital UHF Transmitter Chapter 3, Installation and Setup Procedures of the cabinet and mounted behind the rear door. On the UHF exciter tray, switch the Operate/Standby switch to Standby. The gain and phase controls on the front panel of the UHF amplifier tray were adjusted at the factory to attain 100% output of the transmitter and should not need to be readjusted.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions Chapter 4 Circuit Descriptions 4.1 (A4) UHF Exciter Tray (12941111; Appendix C) voltage measured at TP2 is typically +1.2 VDC. The next doubler stage consists of Z2 with bandpass filter C40 and L12 tuned to the fourth harmonic of the fundamental frequency (268 MHz to 528 MHz). The fourth harmonic is then amplified by U5 and fed through another bandpass filter tuned to the fourth harmonic consisting of L14 and C44 (268 MHz to 528 MHz).
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions exactly on frequency. Capacitors C4 and C5 provide the positive feedback necessary for oscillation. VCXO frequency. The PLL board uses an external 10-MHz signal as the reference unless it is missing, then an internally generated 10-MHz signal is used. The two 10-MHz reference signals are connected to the K1 relay and the selected reference to U1.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions is above the reference set by R13 and R14, which is connected to pin 2 of U3A, the output of U3A stays high. The high connects to gates of Q4 and Q9, which are biased on and cause their drains to go low. The low from the drain of Q9 is wired to J8, pin 6, for connection to a remote external 10-MHz present indicator.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions bias is set by R12. The AFC output at J6 on the board connects to the VCXO on the UHF generator board. The PLL circuit will maintain the very accurate VCXO output because any change in frequency will be corrected by the AFC error voltage. 4.1.5 (A1) Power Entry Module Assembly (1227-1206; Appendix D) The power entry module assembly provides overvoltage and surge protection for the input AC lines that connect to the exciter tray.
0-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions has three stages of correction. Each stage has a variable threshold and magnitude control. The threshold control determines the point where the gain is changed and the magnitude control determines the gain change once the breakpoint is reached.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions VDC and diodes CR11 and CR12 provide a .9-VDC reference voltage that is used to temperature compensate for the two diodes in the corrector stage. and R40 form an L-pad that lowers the level of the signal. The signal is applied to amplifier U6 to compensate for the loss in level through the L-pad. After the signal is amplified by U6, it is applied to a third stage through T6.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions select enable/disable jumper W11 on J29 controls whether the Modulator Select command at J30 controls the operation of the relays. With jumper W11 on J29, pins 1 and 2, the Modulator Select command at J30 controls the operation of the relays but, with jumper W11 on J29, pins 2 and 3, the modulator is selected all of the time. the tray cover is off and the tray is in a high RF environment.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions VDC line. When the detected input signal level at U9A, pin 2, falls below this reference threshold, approximately 10 dB below the normal input level, the output of U9A, pin 1, goes to the +12 VDC rail. This high is connected to the base of Q2, which is forward biased, and creates a current path from the -12 VDC line, through the red Input Level Fault Indicator LED DS1 (which lights), resistor R54, and transistor Q2 to +12 VDC.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions series diode CR3, and finally through R9 to ground. This path forward biases CR3 and causes it to act as a relatively lowvalue resistor. The larger current flow increases the voltage drop across R9 and tends to turn off the diodes CR1 and CR2, causing them to act as high-value resistors.
300-Watt Digital UHF Transmitter reference voltage is then connected to diode CR5 through choke L11. Chokes L11 and L12 form a high impedance for the RF that serves to isolate the op-amp ICs from the IF. After the signal is amplified by U2, it is applied to the second corrector stage through T2. This corrector and the third corrector operate in the same fashion as the first. All three corrector stages are independent and do not interact with each other.
300-Watt Digital UHF Transmitter motor-driven pot controlled by switch S1 on the board or screwdriver adjust pot R1 on the front panel of the UHF exciter tray. An external power raise/lower switch can be used by connecting it to jack J10, at J10-11 power raise, J10-13 power raise/lower return, and J10-12 power lower on the rear of the UHF exciter tray. S1, or the remote switch, controls relays K1 and K2 which, in turn, the control motor M1 that moves variable resistor R75.
300-Watt Digital UHF Transmitter ALC circuit as well as the AGC reference to the transmitter control board (12651311). Voltage TP4 should be the same in either the normal or the encoded video mode. Monitor J9, pins 3 and 4, with a spectrum analyzer, check that the board is in the AGC mode, and tune C103 to notch out the aural IF carrier. 4.1.7.11 Fault Command The ALC board also has circuitry for an external mute fault input at J19, pin 6.
300-Watt Digital UHF Transmitter (digital) calibration control that is adjusted for a 100% digital reading, to amplifier U2B. The amplified digital output is connected to comparator U2C. The other input to U2C is the level set by aural null adjust R51, which is not used with digital. Pots R51 and R20 should be set full CCW. The offset null adjust R48 is adjusted for 0% digital power with the transmitter in Standby. The adjusted output is amplified by U3D and connected to the other input of U2C.
300-Watt Digital UHF Transmitter leak from one input port to any of the other ports. This property is enhanced by having inputs and outputs of the mixer at 50Ω impedance. The reactive filter that is externally connected to J3 of the board does not appear as a good 50-Ω load at all frequencies. The pad, in the output line of the board, consists of R5, R4, R6, and R7. The pad buffers the bad effects of the reactive filter load and makes it appear as a 50-Ω impedance.
300-Watt Digital UHF Transmitter -12 VDC line that is external to the UHF upconverter board; the -12 VDC is then applied to the rest of the board. 4.1.10 (A17) Transmitter Control Board (1265-1311; Appendix D) The transmitter control board provides the system control functions and the operational LED indications that can be viewed on the front panel of the transmitter. The main control functions are for Operate/Standby and Auto/Manual selection.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions Auto/Manual switch S2 on the front panel of the tray. 4.1.10.3 Automatic Control of the Transmitter When the S2 switch is set to the Auto position, the operation of the transmitter is controlled by the fault circuits and will stay in Operate even if Operate/Standby switch S1 is switched to Standby.
300-Watt Digital UHF Transmitter 13. With U5A, pins 1 and 2, low, the output at pin 3 goes high. With pin 12 of U5D high, the output of U5D at pin 11 goes low. When U5A, pin 3, is high, it biases on Q20, which applies a pull-down enable to the Operate switch. A low at U5D, pin 11, biases off Q19, which removes any pull-down to the Standby switch. The transmitter is switched to Operate. 4.1.10.
300-Watt Digital UHF Transmitter above 170° F, it closes and applies a low to J8-1 or J12. The low connects to Q3, which is biased off, and to the red Overtemperature LED DS6, which is biased on. The drain of Q3 goes high and connects to pins 11 and 12 of U4B. The high at the input to U4B causes it to go high and switches the system to standby. This removes the Operate enable commands to any external amplifier trays.
300-Watt Digital UHF Transmitter J8-12, which can light any remote receiver fault indicator that is connected to it. 4.1.10.5 Metering The front panel meter connects to J3-1(-) and J3-2(+) on the board; this is the output of switch S3. The front panel meter has four metering positions that are controlled by switch S3: % Forward Power, % Reflected Power, % Exciter, and ALC.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions to U3 and U4; U3 and U4 are voltageregulator ICs for the +12 VDC. The voltage-regulated and current-limited +12-VDC output of U3 connects to J4, pins 1, 2, 3, and 4, which is one of the +12-VDC outputs of the board. The green LED DS3 will be lit if +12 VDC is present to J4; C7 and C8 are bypass capacitors. The +12 VDC output of U4 connects to J5, pins 1, 2, 3, and 4, which is another one of the +12-VDC outputs of the board.
300-Watt Digital UHF Transmitter signals. The board also provides for the frequency response and gain adjustment of the IF signal. The circuitry for the I and Q signals to the mixers is identical. The I signal enters the board at J3-2. Diodes CR1 to CR3 provide surge protection to buffer U4. The output of U4 is fed through variable resistor R32, the gain pot for the unmodulated signal. The circuit consisting of U1 and its associated components provides the DCoffset adjustment at the input of U5.
300-Watt Digital UHF Transmitter indicator is driven from U4, pin 60, through field effect transistors (FETs) Q2 to J9-4. The 10-MHz reference present indicator is driven from the collector of Q1 through transistor Q3 and associated components to J9-2. Chapter 4, Circuit Descriptions 4.2.4 (A3) LED Board (1561-1204; Appendix D) J13 and J14 on this card select between the various input formats. These jumper settings are outlined in Chapter 5, Detailed Alignment Procedures, of this manual.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions 4.2.7 (A10) DC Power Supply Board (1047033; Appendix D) 4.2.9 (A4) VSB Symbol Generator Board (1049396; Appendix D) The DC power supply board generates both positive and negative 12 and 5 VDC, as well as positive 3.3 VDC, at a current level that is sufficient to operate the other boards in the modulator tray. Visual indicators, using LEDs, are provided on the board to show the normal operation of each voltage regulator.
300-Watt Digital UHF Transmitter frequency of the channel of operation, the assembly has approximately 9 dB of gain. Chapter 4, Circuit Descriptions voltage before it is connected to the base. The +28-VDC bias voltage connects through FL1, an RF bypass feed-through capacitor, that is mounted on the amplifier assembly to E1 on the board. The board has a self-bias protection circuit that uses zener diodes VR1 and VR2.
300-Watt Digital UHF Transmitter The RF input to the board is connected to the input of the first 2-way splitter that contains R1. R1 is a balancing resistor in which any RF due to mismatching in the first splitter will be dissipated. One of the two outputs from the splitter connects to another 2-way splitter that contains R2. R2 is a balancing resistor in which any RF due to mismatching in the splitter will be dissipated.
300-Watt Digital UHF Transmitter J4-2. U3 has a very high input impedance that makes the IC less sensitive to changes in the video level. Diode CR4 provides temperature compensation for diode CR3. An input signal level of approximately +17 dBm is enough to give a 1-VDC level at the output of U1B. The +12 VDC needed for the operation of U1 IC on the board is generated from the +28 VDC which enters at J4, pin 7.
300-Watt Digital UHF Transmitter the bias, operating currents of the transistors. The base voltage is RF bypassed by C229, C202, C207, C208, C209, and C210 and applied to the bases through R202 and R203. The collectors are impedance matched to 12.5Ω by C216, C220, C222, C223, and C219, which can be adjusted for peak output with best linearity and lowest current. C225 provides AC coupling and DC blocking for the output signal to the combiner.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions Table 4-1. Fuses, Idling Currents, and Voltage Settings for the Class AB Amplifier Devices SWITCH POSITION AMPLIFIER MODULE TRANSISTOR DEVICE BIAS ADJUST POT IDLING CURRENT VOLTAGE SETTING FUSE I1 A4-A1 Q1 R6 *5 Amps 50 mV F1 I2 A4-A3 Q201 R206 600 mA 6.0 mV F2 I3 A4-A3 Q101 R106 600 mA 6.0 mV F3 I4 A5-A2 Q201 R206 300 mA 3.0 mV F4 I5 A5-A2 Q101 R106 300 mA 3.
300-Watt Digital UHF Transmitter 4.3.11.1 Phase Control The phase control pot on the front of the tray connects to J8-1 (+26 VDC), J8-3 (phase I/P), and J8-4 (RTN) on the board. The phase-control output connects from J7 on the board to the input of the phase-control circuit on the variable gain/phase board (1265-1425). 4.3.11.2 Automatic and Manual Gain Control Circuits The amplifier control board contains the AGC function for the UHF amplifier tray in which it is mounted.
300-Watt Digital UHF Transmitter A sample of the reflected power output of the tray is applied to jack J2-1 and J2-2 of the board from the dual peak detector board, single supply. The reflected power sample is connected through R21 and R22 to U1B, a buffer amplifier. The output of U1B is split, with one part going to the VSWR threshold circuit, another sample connected to J2-5 for remote metering, and the final sample applied to the meter at position 2 on S2, the front panel meter switch.
300-Watt Digital UHF Transmitter the branch consisting of R10 and DS1, a green LED current indicator; as a result, it has the same voltage across it. The collector bias voltage drop biases on the green LED DS1. The current flow through R10 and DS1 gives a visual indication of the current draw of Q1 by the relative brightness of DS1. The higher the collector current of the transistor, the larger the voltage drop across the metering resistor. This, in turn, increases the voltage across DS1 and R10.
300-Watt Digital UHF Transmitter Chapter 4, Circuit Descriptions amplifier control board connects to FL4 and FL5 on the assembly and is wired to J5 on the board. The phase control input from the amplifier control board connects to FL2 and E1 on the assembly and is wired to J4 on the board. The input fault to the amplifier control board connects to FL3 on the assembly and is wired to J6-1 on the board. E1 on the assembly connects to J3-4 on the board.
300-Watt Digital UHF Transmitter The output connects to J2 on the board. A sample of the output is detected by CR10 and connected to TP4. A DVM can be connected to TP4 to give a voltage indication of the RF output level. The +26 VDC connects to the board at J3-3 and is split, with one half connected to the two, class A amplifier circuits. The other half of the +26-VDC input is filtered, isolated by L4 and C13, and connected to U1.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures Chapter 5 Detailed Alignment Procedures This transmitter was aligned at the factory and should not require additional alignments to achieve normal operation. The digital IF connects to J6 on the rear of the UHF exciter, which is cabled to the delay equalizer board, and then to the IF relays on the ALC board. To operate using the digital input, the modulator select must be present.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures phasing adjustments to the four UHF amplifier trays. operating position. The detected IF signal level at J19-2 of the ALC board is connected to the transmitter control board. This board distributes the level to the two UHF amplifier trays where it is used as a reference for the automatic gain control (AGC) in each amplifier tray. Verify that all red LEDs on the ALC board are extinguished.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures Table 5-2. Center Frequencies for the Delay Equalizer Sections DELAY EQUALIZER SECTION 1 2 3 4 5 CENTER FREQUENCY 46.5 MHz 44 MHz 44 MHz 41.5 MHz 44 MHz 5.1.2 IF Phase Corrector Adjustment output signal. A typical digital spectrum is shown in Figure 5-1.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures 5.1.3 (A15-A1) UHF Generator Board (1565-1109) voltmeter is used, the harmonic frequencies must be minimized to prevent interference with other channels. The (A15-A1) UHF generator board is mounted in (A15) the UHF generator enclosure. This procedure should be performed to align this board.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures Table 5-3. Switch Positions SWITCH SW1-8 SW1-7 SW1-6 SW1-5 POSITION N5 N4 N3 N2 SW2-8 SW2-7 SW2-6 SW2-5 N1 N0 A5 A4 SW3-8 SW3-7 SW3-6 SW3-5 A3 A2 A1 A0 Table 7-2 shows the proper switch positions according to channel frequencies. Note: N7 and N6 are fixed values and can not be programmed. Table 5-4.
300-Watt Digital UHF Transmitter CHANNEL 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 FREQUENCY (MHz) 655 661 667 673 679 685 691 697 703 709 715 721 727 733 739 745 751 757 763 769 775 781 787 793 799 805 811 817 823 829 835 841 847 Chapter 5, Detailed Alignment Procedures N N7-N0 A A5-A0 81 82 83 84 84 85 86 87 87 88 89 90 90 91 92 93 93 94 95 96 96 97 98 99 99 100 101 102 102 103 104 105 105 01010001 01010010 01010011 01010100 01010100 010101
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures (A8) the amplifier control board (12651414), to the AGC On position. power screwdriver adjust pot on the front panel of the UHF exciter tray. The amplifier tray can then be adjusted as needed to achieve the 100% output. As shipped, the exciter was preset to include linearity (gain vs. level) and phase (phase vs. level) pre-distortion.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures of that tray until a peak is reached or until the end-of-travel is achieved. If the end-of-travel is reached, repeat the above procedure, replacing the 2-inch length of cable with a 4-inch length of cable. Once a peak is reached, move the phase control that is full CCW up two turns and repeat it using the phase control on the other tray. This allows both trays to have some range of adjustment. 5.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures 5.3.1 (A11) VSB Modulator Interface Board (1561-1205; Appendix D) signal-processing functions outlined in the ATSC specification for 8-VSB modulation. These functions involve data randomization, the Reed Solomon encoder, data interleaver, and the trellis encoder. These functions are implemented in programmable logic chip U1 on the symbol generator card. In addition, this card performs the linear equalization function.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures Table 5-6. Jumper Configurations for the Symbol Generator Board REFERENCE DESIGNATOR J5 J8 J11 J23 J24 J26 J27 J28 J29 SW1 DT830A, Rev. 1 FUNCTION SETTING 19.39M/2.42M clock select: Used for test purposes only. 1-2 selects 2.42 MHz, 2-3 selects 19.39 MHz /DPWEN, 2.69 MHz clock select: Used for test purposes only. 1-2 selects 2.69 MHz, 2-3 selects /DPWEN clock. 10.76 MHz/32 MHz clock select: Used for test purposes only.
300-Watt Digital UHF Transmitter REFERENCE DESIGNATOR Chapter 5, Detailed Alignment Procedures FUNCTION SETTING 4-position DIP switch: Used to adjust the gain of the linear equalizer when J28 is set to 1-2. SW2 Positions 1-4: All positions should remain off during normal operation. Divide – Sw 1,2 On, On – divide by 1 On, Off – divide by 2 Off, On – divide by 4 Off, Off – divide by 8 Divide – Sw 3,4 On, On – multiply by 1 On, Off – multiply by 1.25 Off, On – multiply by 1.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures Table 5-7. Jumper Configurations for the VSB Filter Board REFERENCE DESIGNATOR J2, J3 J6-J9 J10, J12 J11, J13 J14 J15 J16 J17 J19 J19 J25 J28 DT830A, Rev. 1 FUNCTION SETTING Impulse Select/Clock Select: Used for board testing purposes. When both are placed in position 2-3, the impulse response of the I and Q filters appear at the I and Q even in the absence of any input to the board.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures The potentiometers on this board consist of the I and Q gain and offset adjustments. Since the overall gain balance between the I and Q channels will be adjusted in the vector modulator, the gain is not critical. As a result, gain potentiometers R50 and R71 should be set to the middle of their range. The offset potentiometers are adjusted in the following order: There is one jumper, J2, to enable or disable the TEST mode.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures Once the DIP switches are set, and there is a 10-MHz reference source present at the rear of the tray, the board will begin the process of phase locking the VCXO. There are three amber LEDs on the board that indicate the progress of the PLL circuit. These LEDs have been designated Step 1, Step 2, and Step 3. combined with combiner Z2 to produce the final IF signal centered at 44 MHz.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures The DC outputs (+15, +5, and -15 VDC) from the switching power supply (1049886) are directed to jack J1. The voltages are then filtered by C1 to C6 and fed to voltage regulators U1 to U7. The outputs are protected from overcurrent conditions by the regulators. The regulators are designed to fold back the voltage if a short-circuit condition occurs externally and will continue to do so until the short is eliminated.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures are adjusted until there is no leakthrough of the 46.69056 MHz on the spectrum analyzer. 5.3.12 I and Q Baseband Frequency Response Adjustments 1. With the setup in the same configuration as it was in step 3 of the Local Oscillator Leak-Through Adjustment procedure, move the spectrum analyzer back to J5. 2. Using the MENU button, go to the OPERATING MODE menu. Use the up arrow to select NORMAL. 3.
300-Watt Digital UHF Transmitter Chapter 5, Detailed Alignment Procedures 5.4 Output Power Level assembly. Adjust R39 on the visual/aural metering board for a 20% reading in the Reflected Output Power position. Using a forward-calibrated coupler and an HP power meter, or equivalent, adjust the output power for a reading of 500 watts out of the bandpass filter on the true average power meter.
APPENDIX A SAMPLE LOG REPORT SHEET
300-Watt Digital UHF Transmitter Appendix A, Sample Log Report Sheet UHF Exciter % Output Power (0-120)= ____________% ALC (0-1 V)= ____________________V% % Exciter (0-120)= ______________% Reflected (0-120)= ______________% UHF Amplifier Trays (A6) AGC Voltage (0-10 V)= _____________V % Reflected Power (0-120)= ________% % Output Power (0-120)= ___ _____% Power Supply Voltage (0-30 V)= ______V (A7) AGC Voltage (0-10 V)= _____________V % Reflected Power (0-120)= ________% % Output Power (0-120)= ___
APPENDIX B TYPICAL OPERATIONAL READINGS
300-Watt Digital UHF Transmitter Appendix B, Typical Operational Readings UHF Exciter ALC=.8 VDC. % Exciter=The level is as needed to attain 100% output power from the transmitter.
APPENDIX C ASSEMBLY DRAWINGS
300-Watt Digital UHF Transmitter Appendix C, Assembly Drawings and Parts Lists DT830A Transmitter Block Diagram.........................................................1127833 Transmitter Interconnect ...........................................................1127837 Rack Plan for DT830A ................................................................1127836 AC Distribution Assembly, Narrow Interconnect.........................................................................
APPENDIX D SUBASSEMBLY DRAWINGS
300-Watt Digital UHF Transmitter Appendix D, Subassembly Drawings UHF Filter Schematic........................................................................................ 1007-3101 +12-Volt, 2-Amp Power Supply Board Schematic........................................................................................ 1128-3504 IF Phase Corrector Board Schematic........................................................................................ 1227-3250 1-Watt Amplifier Board Schematic.................
300-Watt Digital UHF Transmitter Appendix D, Subassembly Drawings Single Stage Amplifier Assembly, High Band, Class A (Made from a Generic Single Stage Amplifier Board, Class A [1265-1415]) Schematic........................................................................................ 1265-3417 Single Stage Amplifier Assembly, Low Band, Class A (Made from a Generic Single Stage Amplifier Board, Class A [1265-1415]) Schematic................................................................................
300-Watt Digital UHF Transmitter Appendix D, Subassembly Drawings LED Board Schematic........................................................................................ 1561-3204 8-VSB Modulator Interface Board Schematic........................................................................................ 1561-3205 VSB Filter Board Schematic........................................................................................ 1561-3301 UHF Generator Board Schematic................................
APPENDIX E DT830A SYSTEM SPECIFICATIONS