INSTRUCTION MANUAL 430B 1-kW VHF High Band 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.
1000 Watt VHF High Band 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 Procedure ....................................................... 1-1 Safety.......................................................................................... 1-1 Maintenance..................................................................................
1000 Watt VHF High Band Transmitter Table of Contents TABLE OF CONTENTS (continued) 5.7 Calibration of the Forward Output Power Level of the Transmitter ............. 5-5 5.8 Calibration of the Reflected Output Level of the Transmitter..................... 5-5 5.9 2-Way Combiner Assembly ............................................................... 5-6 5.10 Bandpass Filter Assemblies.............................................................. 5-6 5.11 VHF High Band Amplifier Tray .....................
1000 Watt VHF High Band Transmitter Table of Contents LIST OF FIGURES 4-1 4-2 1 kW Minimum Ventilation Configuration ....................................... 4-4 Chassis Trak Cabinet Slides ........................................................ 4-5 5-1 Waveform ..............................................................................5-12 430B, Rev.
1000 Watt VHF High Band 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 430B Major Trays and Assemblies ................................................ 2-1 VHF Exciter Tray Meters............................................................. 2-3 VHF Exciter Tray Switches .......................................................... 2-4 VHF Exciter Tray Fault Indicators ................................................. 2-4 VHF Exciter Tray Samples ..................
1000 Watt VHF High Band Transmitter Chapter 1, Introduction Chapter 1 Introduction the appendices. Section titles in the text for assembly or tray descriptions or alignment procedures also indicate the associated drawing(s) and the relevant appendix that contains the drawing. Sections describing vendor-supplied items, such as meters and power supplies, do not contain this information. 1.
1000 Watt VHF High Band Transmitter Chapter 1, Introduction aerosol cleaners. Use a damp cloth for cleaning. 1.5 Material Return Procedure To insure the efficient handling of equipment or components that have been returned for repair, Axcera requests that each returned item be accompanied by a Material Return Authorization Number (MRA#). Ventilation – Openings in the cabinets and tray front panels are provided for ventilation.
1000 Watt VHF High Band Transmitter Chapter 1, Introduction Axcera can also be contacted through email at info@axcera.com and on the Web at www.axcera.com. or alteration. Axcera's exclusive liability for any personal and/or property damage (including direct, consequential, or incidental) caused by the breach of any or all warranties, shall be limited to the following: (a) repairing or replacing (in Axcera's sole discretion) any defective parts free of charge (F.O.B.
1000 Watt VHF High Band Transmitter Chapter 2, System Description, Maintenance and Remote Interface Connections Chapter 2 System Description, Maintenance and Remote Interface Connections The 430B is a complete 1000 watt VHF high band solid state internally diplexed television transmitter that operates at a nominal visual output power of 1000 watts peak sync and an average aural output power of 100 watts, at an A/V ratio of 10 dB, 10% sound, or 50 watts at 13 dB, 5% sound. 2.
00 Watt VHF High Band Transmitter Chapter 2, System Description, Maintenance and Remote Interface Connections In the VHF amplifier tray, a forward power sample and a reflected power sample from the 3-way combiner board are connected to the AGC Control Board that peak-detects the samples and connects them to the front panel meter of the tray. Operate, check that a dummy jumper plug, with a jumper between pins 21 and 22, is connected to jack J9 on (A12) the A/V input and remoter interface assembly.
1000 Watt VHF High Band Transmitter Chapter 2, System Description, Maintenance and Remote Interface Connections 2.2.1 VHF Exciter Tray Table 2-2. VHF Exciter Tray Meters METER Meter (A4-A18) 430B, Rev. 0 FUNCTION This meter reads power in terms of a percentage of the calibrated output power level on the upper scale. The voltage level or frequency level is read on one of the bottom two scales. A full-scale reading on the top scale is 120%.
1000 Watt VHF High Band Transmitter Chapter 2, System Description, Maintenance and Remote Interface Connections Table 2-3. VHF Exciter Tray Switches SWITCH Transmitter S1 Operate/Standby Mode Select S2 Auto/Manual Power Adjust (R1) FUNCTION The momentary switch S1 applies a ground to K1, a latching relay on the transmitter control board. K1 will switch either to Operate or to Standby depending on which direction S1 is pushed.
1000 Watt VHF High Band Transmitter Chapter 2, System Description, Maintenance and Remote Interface Connections 2.2.2 VHF High Band Amplifier Tray Table 2-6. VHF High Band Amplifier Tray Switches SWITCH On/Off Circuit Breaker CB1 Switch S1, Meter Switch S2, Meter 430B, Rev. 0 FUNCTION Switches 220 VAC through a 15 amp circuit breaker protection device. The switch lights if AC is present. The AC is applied to the switching power supply in the tray.
1000 Watt VHF High Band Transmitter Chapter 2, System Description, Maintenance and Remote Interface Connections Table 2-7. VHF High Band Amplifier Tray Fault Indicators INDICATOR Overdrive (DS1) Enable (DS2) Module Status (DS3) VSWR Cutback (DS4) Overtemp (DS5) DESCRIPTION Indicates that the level of drive is too high. The protection circ uit will limit the drive level to the set threshold. The fault is generated on the overdrive protection board.
1000 Watt VHF High Band Transmitter Chapter 2, System Description, Maintenance and Remote Interface Connections upper middle facing the rear of the cabinet. The panel contains the terminal block TB1 to which the 220 VAC input connects. lead to a thermal shutdown or premature failure of the affected trays. When the front panels of the trays become dust covered, the top covers should be removed and any accumulated foreign material should be removed.
1000 Watt VHF High Band Transmitter Chapter 2, System Description, Maintenance and Remote Interface Connections Table 2-10. 430B Remote Interface Connections to (A12) the A/V Input and Remote Interface Assembly FUNCTION REMOTE JACK/PIN NUMBER Transmitter Enable Interlock J9-21 Transmitter Enable Interlock Rtn. J9-22 INTERFACE TYPE J9-21 and J9-22 must be jumpered together for normal operation. The (1176-1038) jumper jack should be used.
1000 Watt VHF High Band Transmitter FUNCTION VSWR Cutback Indicator VSWR Cutback Indicator Return Chapter 2, System Description, Maintenance and Remote Interface Connections REMOTE JACK/PIN NUMBER J9-23 INTERFACE TYPE 50 mA max current sink J9-24 Video Loss (Fault) Indicator Video Loss (Fault) Ind. Rtn.
1000 Watt VHF High Band 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 430B 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.
1000 Watt VHF High Band Transmitter Chapter 3, Installation and Setup Procedures determine how to accomplish this. The options are air conditioning, ventilation, or a combination of the two. Air conditioning is always the preferred method and is the only way to create anything close to an ideal environment. transmitter. Condensation may occur on, or worse in, the transmitter under certain conditions.
1000 Watt VHF High Band Transmitter Chapter 3, Installation and Setup Procedures not be carried in with the cooling air. 5. The exhaust should be located as high as possible. Some ducting is usually required to insure the complete flushing of heated air with no stagnant areas. 6. The filter area must be large enough to insure a maximum air velocity of 300 feet per minute through the filter. This is not a conservative number but a neverexceed number.
1000 Watt VHF High Band Transmitter Chapter 3, Installation and Setup Procedures Figure 3-1. 1 kW Minimum Ventilation Configuration Remove the cabinet and the trays from the crates and boxes. Remove the straps that hold the cabinet to the shipping skid and slide the cabinet 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 ma ke assembly of the transmitter much easier.
1000 Watt VHF High Band Transmitter Chapter 3, Installation and Setup Procedures Figure 3-2. Chassis Trak Cabinet Slides Open the rear door. Inspect the interior of the cabinet for packing materials and carefully remove any packing materials that are found. Slowly slide each tray in and out to verify that they do not rub against each other and have no restrictions to free movement. 3.4 Main AC Connection Once the cabinet is in place, and the trays are checked for damage, the main AC hookup can be made.
1000 Watt VHF High Band Transmitter Chapter 3, Installation and Setup Procedures and operation procedures that follow before applying power to the transmitter. approximately 7 seconds, the transmitter will automatically revert to Standby and, when the video signal is restored, the transmitter will quickly return to Operate. 3.
1000 Watt VHF High Band Transmitter Chapter 3, Installation and Setup Procedures If a dummy load is connected to the transmitter, switch the unit to Standby and switch off the main AC circuit breaker. Remove the dummy load and make all of the connections that are needed to connect the transmitter to the antenna. Switch the main AC circuit breaker on and the Operate/Standby switch to Operate. Adjust the output power screwdriver pot to achieve an output of 100%. 100%.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions Chapter 4 Circuit Descriptions approximately 0 dBm, the mini-jumper should be in the high gain position between pins 1 and 2 of jack J11. If the input level is approximately +10 dBm, the mini-jumper should be in low gain position between pins 2 and 3 of jack J11. The balanced audio is then connected to buffer amplifier U2A whose input level is determined by the setting of balanced audio gain pot R13.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions is then applied though the SCA gain pot R24 to the summing point at pin 13 of U2D. 4.5 MHz VCO IC U10; this sets up a phase lock loop circuit. The 4.5 MHz VCO will maintain the extremely accurate 4.5 MHz separation between the visual and aural IF signals; any change in frequency will be corrected by the AFC error voltage. 4.1.1.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions produces a modulated visual IF + aural IF output at output jack J20 on the board. The clamp portion of the board maintains a constant peak of sync level over varying average picture levels (APL). The modulator portion of the board contains the circuitry that generates an amplitude-modulated vestigial sideband visual IF signal output that is made up of the baseband video input signal (1 Vpk-pk) modulated onto an externally generated 45.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions increase or decrease its output, as needed, to bring the peak of sync back to the correct level as set by R152 and R12. This voltage level is applied through U3B to Q2. In the Manual position, jumper W7 on J4 is in the Clamp -Off position, between pins 1 and 2, and adjustable resistor R41 provides the manual clamp bias adjustment for the video that connects to Q2. low-impedance, clamped video output at pin 1. 4.1.2.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions The visual IF from J19 is amplified by U10 and U11 and routed through the vestigial sideband filter network, consisting of T1, FL1, and T2, and produces a vestigial sideband visual IF signal output. The filtered vestigial sideband visual IF is amplified by U7 and connected to a T -type attenuator. R62 can be adjusted to set the visual IF gain; this is the amount of visual IF signal that is coupled to amplifier IC U8.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions 4.1.3 (A6) Delay Equalizer Board (1227-1204; Appendix D) 4.1.4 (A7) IF Carrier Oven Oscillator Board (1191-1404; Appendix D) The delay equalizer board provides a delay to the video signal, correction to the frequency response, and amplification of the video signal. The IF carrier oven oscillator board generates the visual IF CW signal at 45.75 MHz for NTSC system "M" usage.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions Q4 drives two different output circuits. One output is directed through voltage dividers R14 and R15 to jack J2 that can connect to a frequency counter. While monitoring J2 the oscillator can be set exactly on the operating frequency (45.75 MHz) by adjusting C17. The output at J2 is at a power level of approximately -2 dBm, which is sufficient to drive most frequency counters.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions video loss cutback, and the threshold detector circuits will only operate when jumper W3 on jack J6 is in the Auto position, between pins 1 and 2. Without the threshold detector, and with the pindiode attenuator at minimum, when the signal is restored it will overdrive the stages following this board. 4.1.5.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions input signal level to the detector at TP3 falls below this reference threshold, which acts as a loss of sync detector circuit, the output of U9C and U9D goes towards the -12 VDC rail and is split, with one part biasing on transistor Q5. A current path is then established from the +12 VDC line through Q5, the resistors R69, R137, and the red LED DS3 (video loss indicator), which becomes lit.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions The output of U1 is available, as a sample of the pre-correction IF for troubleshooting purposes and system setup, at jack J2. The IF signal is then connected to the linearity corrector portion of the board. corrector is set by controlling where CR4 and CR5 turn on. This is accomplished by adjusting cut-in resistor R34; R34 forms a voltage-divider network from +6.8 VDC to ground.
1000 Watt VHF High Band Transmitter Following the bandpass filter, the signal is split using L24, L25, and R89. The signal passing through L24 is the main IF path through the board. A sample of the corrected IF signal is split off and connected the IF sample jack J10. The IF connects to jacks J27 and J28. These jacks control whether a 6 dB pad is included in the circuit by the positioning of jumpers W9 and W10. The 6 dB pad-in is when jumpers W9 and W10 are connected between pins 2 and 3 on J27 and J28.
1000 Watt VHF High Band Transmitter the ALC detector is offset, or complemented, by current taken away from the summing junction. In normal operation, U10A, pin 2, is at 0 VDC when the loop is satisfied. If the recovered or peak-detected IF signal at IF input jack J7 of this board should drop in level, which normally means that the output power is decreasing, the null condition would no longer occur at U10A, pin 2. When the level drops, the output of U10A, pin 1, will go more positive.
1000 Watt VHF High Band Transmitter This establishes a very fast muting action, by reverse biasing CR3, in the event of an external VSWR fault. 4.1.5.12 ±12 VDC Needed to Operate the Board The ±12 VDC connects to the board at J14. The +12 VDC connects to J14-3 and is filtered by L30, L41, and C80 before it is applied to the rest of the board. The -12 VDC connects to J14-5 and is filtered by L31 and C81 before it is applied to the rest of the board.
1000 Watt VHF High Band Transmitter amplifier U2 to compensate for the loss through the L-pad. U2 is powered through L4 and R10 from the +12 VDC line. After the signal is amplified by U2, it is applied to the second corrector stage through T2 and then to a third corrector stage through T3. The other two corrector stages operate in the same manner as the first; they are independent and do not interact with each other. When jumper W1 on J8 is connected from center to ground, R15 is put in series with ground.
1000 Watt VHF High Band Transmitter loss in level through the L-pad. After the signal is amplified by U6, it is applied to a third stage through T6. The transformer doubles the voltage swing by means of a 1:4 impedance transformation. Resistors R42, R59, R60, and R43 form an L-pad to lower the level of the signal. The signal is applied to amplifier U7 to compensate for the loss in level through the L-pad.
1000 Watt VHF High Band Transmitter The IF input connects to the board at J7 and is fed to mixer Z1 at pin 3 (-3 dBm). Mixer Z1 takes the LO input at pin 1 and the IF input at pin 3 to produce an RF output at pin 8. The RF output at pin 8 (-14 dBm) connects through a pi-type attenuator, made up of R3, R4, and R5, before it is connected to RF output jack J6. Normally, jack J6 is connected by a coaxial jumper to J1 on the board.
1000 Watt VHF High Band Transmitter The +12 VDC needed for the operation of the board is supplied by an external power supply in the tray. The +12 VDC enters the board at J3, pin 3, and is filtered and isolated from the rest of the tray by L5 and C19 before being applied to the entire board. The –12 VDC enters the board at J3, pin 5, and is filtered and isolated from the rest of the tray by L6 and C35 before being applied to the entire board. 4.1.
1000 Watt VHF High Band Transmitter applied to Q2 is also connected to Q5 and Q26, which are biased off, and removes the remote enable at J1-3. The transmitter is now in the Standby mode. 4.1.8.2 Automatic/Manual Switch S2 K2 is a magnetic latching relay that switches the operation of the transmitter to Automatic or Manual using Auto/ Manual switch S2 located on the front panel of the tray.
1000 Watt VHF High Band Transmitter causes the drain of Q18 to go low. The low connects to U3D, pin 12, whose output at pin 14 goes low. The low connects to U5C, pins 8 and 9, which causes its output at pin 10 to go high, and to U5A, pin 1. With Auto/Manual switch S2 in Auto, a low is applied to U5A, pin 2, and to U5D, pin 13. When U5A, pins 1 and 2, is low, its output at pin 3 goes high. When pin 12 of U5D is high, the output of U5D at pin 11 goes low.
1000 Watt VHF High Band Transmitter 4.1.8.6 Overtemperature Fault In this 1 kW VHF transmitter the (A8-A1) thermal switch mounted on the (A8) Combiner Assembly connects to J11-1 & J11-35 on the rear of the VHF Exciter. These connect to J8-1 & J8-35 on the Transmitter Control Board. If the temperature of the thermal switch rises above 170° F, it closes and applies a low to J8-1. The low connects to Q3, which is biased off, and to the red Overtemperature LED DS6, which is biased on.
1000 Watt VHF High Band Transmitter at U3D, pin 14, goes high. A high at this point indicates a fault condition that switches the transmitter to Standby. The low connected to U3A, pin 2, causes its output to go high. The high is connected to Q25, which is biased on, and causes the drain to go low. The low is connected to J8-12, which can light any remote receiver fault indicator that is connected to it. 4.1.8.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions voltage feedback from the external amplifier trays. offset null adjust R48, which are adjusted to set up the visual power calibration. 4.1.9 (A19) Visual/Aural Metering Board (1265-1309; Appendix D) 4.1.9.2 Visual Level Circuit The visual/aural metering board provides detected outputs of the visual, aural, and reflected output samples that are used for monitoring on the front panel meter.
1000 Watt VHF High Band Transmitter that is connected to the plus input of U1C, producing a peak of sync in the signal. The output of U1C is connected to intercarrier notch L3, which is adjusted to filter out the aural and the 4.5-MHz intercarrier frequencies. The visual-withsync output is fed to a peak-detector circuit, consisting of CR5 and U2A, and then fed through visual calibration control R28 to amplifier U2B.
1000 Watt VHF High Band Transmitter The scans in U4 will continue until field effect transistor (FET) Q1 is gated on. The gate of Q1 is connected to pin 13 on U4, which is the maximum count used in the EEPROM, and will provide a reset pulse each time the binary counter goes high on pin 13. The reset pulse, when the drain of Q1 goes low, is applied to the flip-flop and the timer U3, which determines the length of time between the sending of the identification code. R14 is adjusted to set this time interval.
1000 Watt VHF High Band Transmitter occurs, the AGC Control Board generates a Fault Output at J1 that is connected to J4 on the Filter/Amplifier Board. The Fault cuts back the RF Signal level using the Pin Diode Attenuator Circuit located on the Filter/Amplifier Board. The output at J2 of the Phase Shifter Board is directed to J1 the input jack on (A2) an enclosure that contains the filter/amplifier board and the high band driver pallet. 4.2.
1000 Watt VHF High Band Transmitter Chapter 4, Circuit Descriptions 4.2.5 (A3-A2) High Band VHF Amplifier Pallet (P200-VHF-H; Appendix D) RF Output at J5 of the Combiner which connects to J2, the RF Output Jack of the Tray. The RF Output of the Overdrive Protection Board at J5 connects to J1 on (A3-A2) the High Band VHF Amplifier Pallet (P200-VHF-H) made by Delta RF Technology. The pallet amplifies the RF to approximately +45 dBm pk-sync + aural.
1000 Watt VHF High Band Transmitter to Q8. The Low to Q4 turns it Off which extinguishes the Enable Indicator at J108. The Low to Q8 turns it Off which turns On Q7 causing a Low to be applied to Q5 and Q6 that are Biased Off which turns Off the Module Status Indicator. A voltage sample from the Switching Power Supply is applied to Jack J9 Pin 1 of the Board and is connected through R86 to the front panel Meter for monitoring. R86 is adjustable to calibrate the voltage reading on the front panel meter. 4.2.
1000 Watt VHF High Band Transmitter The +28 VDC output of the switching power supply assembly connects to (A8) the Current Metering Board. 4.2.11 (A8) Current Metering Board (1301316; Appendix D) The Current Metering Board distributes the voltages through fuses to the Amplifier Devices on the Filter/Amplifier, High Band Driver Board, the High Band Amplifier Board and the three Final High Band Amplifier Boards. The Fuses F1, F2 & F3 are 15 Amp, F4 is 5 Amp, F6 is 2 Amp and F7 is 1 Amp Fuse.
1000 Watt VHF High Band Transmitter The front panel Meter (A9), using (S1) the Front Panel Selector Switch, monitors the AGC Voltage, % Output Reflected Power, % Forward Power and the Switching Power Supply Voltage (+28 VDC). The Meter in the AGC position will read anywhere from 1 Volts to 2 Volts. The Meter is calibrated in the Power Supply position using R86 located on the AGC Control Board.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures Chapter 5 Detailed Alignment Procedures The 430B transmitter was aligned at the factory and should not require additional alignments to achieve normal operation. jack J3 on (A5) the sync tip clamp modulator board (1265-1302). Connect a baseband audio input (+10 dBm) to the balanced audio input terminal block TB11 (+), TB1-2 (-), and TB1-3 (ground).
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures able to operate using either the separate video and audio baseband inputs or the single 4.5-MHz composite input. The 4.5MHz composite input kit includes a composite 4.5-MHz filter board (12271244) and a 4.5-MHz bandpass filter board (1265-1307). The IF section of the VHF H.B. exciter tray includes adjustments for automatic level control (ALC), linearity (amplitude predistortion), and phase (phase change vs.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures receiver tray is present in the system). DS5 is always on with no receiver. 4.5 MHz bandpass filter board are not used. The tray has been factory tuned and should not need any alignments to achieve normal operation. To align the tray for the 4.5 MHz composite input, apply the 4.5 MHz composite input, with the test signals used as needed, to the video input jack (J1 or J2 [loop-through connections]) on the rear of the tray.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures The output at J6 and J7 on the board should be video only, without the 4.5MHz aural subcarrier. 3. 5.1.4.1.2 (Optional) (A25) 4.5 MHz Bandpass Filter Board (1265-1307; Appendix D) Tune the four stages of the board using the variable inductors (L1-L4) and potentiometers (R7, R12, R17, and R22) until the signal attains the FCC group delay curve. The stages are arranged in order of increasing frequency.
1000 Watt VHF High Band Transmitter 4. Chapter 5, Detailed Alignment Procedures Monitor TP2 with an oscilloscope. Adjust R12, the video gain pot, for 1 Vpk-pk. 5. Change the video input test signal to a multiburst test pattern. While monitoring TP2, adjust C8 and R32 for a flat-frequency response. Change the input video test signal back to the 5-step staircase. 6. Monitor TP2 with an oscilloscope. Adjust pot R41, manual offset, for a blanking level of -0.8 VDC.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures white on the ICPM display, and then adjust R53 for minimum ICPM. 12. Recheck the depth of modulation and, if necessary, adjust R152, depth of modulation. 13. On a spectrum analyzer, adjust pot R70 for a level of approximately -10 dBm at J18. 14. Remove the input video test signal. Place the front panel meter in the video position and, while monitoring the meter, adjust pot R144, zero adjust, for a reading of zero. 15. 16.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures 3. 5. Check the distortion on the aural distortion analyzer (THD=< 0.5%). 6. Disconnect the 600Ω balanced audio input to the tray. Connect a 75Ω stereo audio input (400 Hz at 1 Vpk-pk) to composite audio input jack J3 on the rear of the tray. Follow the procedure in the stereo generator instruction manual for matching the level of the generator to the exciter. Use R17 to adjust the composite audio gain. 7.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures illuminated. Reconnect J32 and make sure that DS1 is extinguished. 3. Jumper W3 on J6 should be in the Manual position. Monitor jack J3 with a spectrum analyzer. 4. With a multiburst video signal present, tune C4 for a flatfrequency response of ±0.5 dB. 5. Before proceeding with the second part of the ALC board alignment, check to see that the IF phase corrector board (1227-1250) is functioning properly.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures correctors. Controls R13, R18, and R23, the magnitude controls, should be set fully CW. Controls R34, R37, and R40 are the linearity cut-in adjustments. 3. 5.1.4.10 (A11-A1) x4 Multiplier Board (1174-1112; Appendix D) 5.1.4.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures 2. The idling current for the amplifier boards are adjusted with no RF drive applied. S1 should be in the Auto AGC position for the normal operation of the transmitter. Adjust C3 and C6 to determine the center frequency. Use C2 and C7 to locate the upper and lower channel-edge shaping. C4 is used to determine the channel bandwidth. 5.1.4.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures The idling current, no RF drive applied, of the device Q1 is set for 250 mA. To set the current, remove the RF drive, measure the voltage across R20 (two 1Ω resistors in parallel on the filter/amplifier board) and adjust R13 for .125 volts (using Ohms’ Law: [E=I x R] : [E=250 mA x .5 Ω] : E=125 mV). This board contains no tuning adjustments. The board takes the +45 dBm input and splits it into three equal +40 dBm outputs. 5.2.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures interface panel. Switch the transmitter to the Operate position. + aural output. However, if the system requires less output power per amplifier tray, adjust each tray by the same amount to give the desired total output power. 3. Adjust the manual gain pot R5 on the AGC control board for: • • Sync + black 0 IRE setup; wattmeter=360 watts Sync + black 7.
1000 Watt VHF High Band Transmitter If the end-of-travel is reached on the phase adjust, reset the phase control CCW and add a 2-inch length of cable to the input of the affected VHF amplifier tray at J1. Readjust the phase of that tray until a peak is reached or until the end-of-travel is achieved. If the end-oftravel is reached, repeat the above procedure and replace the 2-inch length of cable with a 4-inch length of cable.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures control locations drawing, ALC board (1265-1305), to find the adjustments for the first through third linearity corrector stages. Because the stages are cascaded, the order of correction is important. The first stage should cut in near white level, with the cut-in point of the next stage toward black, and with the last stage primarily stretching sync.
1000 Watt VHF High Band Transmitter Chapter 5, Detailed Alignment Procedures located in the VHF exciter. Connect a sync and black test signal to the video input jack of the VHF exciter tray. Switch the transmitter to Operate. and J4, and adjust R39 on the (A19) visual/aural metering board (12651309), in the VHF exciter, for a 20% reading in the Reflected Power position. At this 20% reference power reading, the VSWR LED mounted on the front panel of the exciter should be illuminated.
APPENDIX A SYSTEM SPECIFICATIONS
VHF Solid State Transmitter/Translator 430B/432B - 1000 Watt High Band Transmitter/Translator Visual Performance Aural Performance General Power Output 1000W Power Output (Average) 100W Output Impedance 50 Ω Distortion 0.5% Frequency Range 174 to 216 MHz FM Noise -60 dB Carrier Stability ±250 Hz AM Noise -55 dB Altitude* 8,500 feet Aural to Visual Separation 4.
APPENDIX B SAMPLE LOG REPORT SHEET & TYPICAL OPERATIONAL READINGS
1000 Watt VHF High Band Transmitter Appendix B, Sample Log Report Sheet (A4) VHF Exciter ALC (0 to 1 V) = ____________V % Aural Power (0 to 120) = __________% % Exciter (0 to 120) = ______________% Video (0 to 1 V) = ________________IRE % Reflected (0 to 120) = ____________% Audio (0 to 100 kHz) = ____________kHz % Visual Power (0 to 120) = _________% VHF High Band Amplifier Trays (A6) (A7) AGC Voltage (0 to 10 V) = ___________V AGC Voltage (0 to 10 V) = ___________V % Reflected Power (0 to 120
1000W VHF High Band Transmitter Typical Readings (A4) VHF Exciter ALC = .8 VDC % Exciter = The level needed to attain 100% output power from the transmitter (Typically between 80 & 90%) % Reflected = < 10 % % Visual Power = 100 % (1000 Watts Peak of Sync) % Aural Power = 100 % (100 Watts @ 10 dB A/V Ratio) Video = 1 V at White w/.
APPENDIX C SYSTEM DRAWINGS
1000 Watt VHF High Band Transmitter Appendix C, System Drawings 430B System: 1000 Watt VHF Transmitter Block Diagram ..........................................1303856 1000 Watt VHF Transmitter Interconnect ...........................................1303857 1000 Watt VHF Transmitter Racking Plan ............................................1303855 AC Distribution Assembly Interconnect..............................................................................
APPENDIX D SUBASSEMBLY DRAWINGS
1000 Watt VHF High Band Transmitter Appendix D, Subassembly Drawings AGC Control Board Schematic ..................................................................................1142-3601 Channel Oscillator Board, Dual Oven Schematic ..................................................................................1145-3201 VHF Filter/Mixer Board Schematic ..................................................................................
1000 Watt VHF High Band Transmitter Appendix D, Subassembly Drawings VHF High-Band Filter/Amplifier Board Schematic .....................................................................................1064147 VHF Mixer/Amplifier Enclosure Assembly Interconnect..................................................................................1088069 VHF Filter/Amplifier Board Schematic .....................................................................................
