INSTRUCTION MANUAL DT325B 350 Watt Digital VHF Low 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.
350-Watt Digital VHF LB Transmitter Table of Contents TABLE OF CONTENTS Section Page 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 ..................................................................................................1-2 Contact Information..................................................
50-Watt Digital VHF LB Transmitter Table of Contents TABLE OF CONTENTS (continued) Section Page 4.2 VHF Low Band Amplifier Tray ..................................................................4-5 4.2.1 Phase Shifter Board ......................................................................4-6 4.2.2 Filter/Amplifier Board....................................................................4-6 4.2.3 VHF Low Band Amplifier Board.......................................................4-7 4.2.
350-Watt Digital VHF LB Transmitter Table of Contents LIST OF FIGURES Figure Page 1-1 Brady Marker Identification .............................................................1-1 2-1 2-2 Driver/Amplifier Chassis Assembly Front View ...................................2-1 Rear view Driver/Amplifier Chassis Assembly ....................................2-9 3-1 3-2 3-3 3-4 1 kW Minimum Ventilation Configuration...........................................
350-Watt Digital VHF LB Transmitter Table of Contents LIST OF TABLES Table 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 Page DT325B Assemblies and Trays .........................................................2-1 Controller/Power Supply Front Panel Display .....................................2-2 Controller/Power Supply Front Panel Status Indicators .......................2-2 Controller/Power Supply Front Panel Control Adjustments ..................2-2 VHF Amplifier Front Panel Tray Control Adjustments .........
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction Chapter 1 Introduction This manual explains the installation, setup, alignment, and maintenance procedures for the DT325B 350-watt digital VHF low band 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. diagrams and interconnect drawings provided in the appendices.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction and repair while providing protection from electrical and mechanical hazards. Listed throughout the manual are notes, cautions, and warnings concerning possible safety hazards that may be encountered while operating or servicing the transmitter. Please review these warnings and familiarize yourself with the operation and servicing procedures before working on the transmitter.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction all items sent to the Field Service Department regardless of whether the item was originally manufactured by Axcera. 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, the RMA# is included with the unit. The RMA# is intended to be used for the return of the unit to Axcera.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction F WARNING!!! × HIGH VOLTAGE Ø DO NOT ATTEMPT TO REPAIR OR TROUBLESHOOT THIS EQUIPMENT UNLESS YOU ARE FAMILIAR WITH ITS OPERATION AND EXPERIENCED IN SERVICING HIGH VOLTAGE EQUIPMENT. LETHAL VOLTAGES ARE PRESENT WHEN POWER IS APPLIED TO THIS SYSTEM. IF POSSIBLE, TURN OFF POWER BEFORE MAKING ADJUSTMENTS TO THE SYSTEM.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction EMERGENCY FIRST AID INSTRUCTIONS Personnel engaged in the installation, operation, or maintenance of this equipment are urged to become familiar with the following rules both in theory and practice. It is the duty of all operating personnel to be prepared to give adequate Emergency First Aid and thereby prevent avoidable loss of life. RESCUE BREATHING 1. Find out if the person is breathing. You must find out if the person has stopped breathing.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction dBm, dBw, dBmV, dBµV, & VOLTAGE EXPRESSED IN WATTS 50 Ohm System WATTS 1,000,000,000,000 100,000,000,000 10,000,000,000 1,000,000,000 100,000,000 10,000,000 1,000,000 100,000 10,000 1,000 100 50 20 10 1 0.1 0.01 0.001 0.0001 0.00001 0.000001 0.0000001 0.00000001 0.000000001 0.0000000001 0.00000000001 0.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction USEFUL CONVERSION FACTORS TO CONVERT FROM TO MULTIPLY BY mile (US statute) kilometer (km) inch (in) millimeter (mm) inch (in) centimeter (cm) inch (in) meter (m) foot (ft) meter (m) yard (yd) meter (m) mile per hour (mph) kilometer per hour(km/hr) mile per hour (mph) meter per second (m/s) pound (lb) kilogram (kg) gallon (gal) liter U.S. liquid (One U.S. gallon equals 0.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction RETURN LOSS VS. VSWR 0 -10 -20 R E -30 T U R N dB L O S S -40 -50 -60 -70 1.001 1.01 1.1 VSWR DT325B, Rev. 0 1-8 2.
350-Watt VHF LB Digital Transmitter Chapter 1, Introduction ABBREVIATIONS/ACRONYMS AC Alternating Current FM Frequency modulation AFC Automatic Frequency Control Hz Hertz ALC Automatic Level Control ICPM Incidental Carrier Phase Modulation AM Amplitude modulation I/P Input AGC Automatic Gain Control IF Intermediate Frequency AWG American wire gauge LED Light emitting diode BER Bit Error Rate LSB Lower Sideband BW Bandwidth MPEG Motion Pictures Expert Group DC Direct Current O/P
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections Chapter 2 System Description, Maintenance and Remote Control Connections A1 A5 A4 Figure 2-1: Driver/Amplifier Chassis Assembly Table 2-1: DT325B Major Assemblies and Trays ASSEMBLY DESIGNATION A24 A2 A2-A11 A2-A1 A2-A5 A2-A4 A3 TRAY/ASSEMBLY NAME ASSEMBLY NUMBER Axciter Modulator Driver/Amplifier Chassis Assembly Backplane Board Downconverter Module Upconverter Module Control/Power Supply Mod
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections 2.2.1: (A4) Exciter Control/ Power Supply Assembly, LXB, 220VAC (1310835; Appendix C) w/Switches Board (1307977). The Assembly also contains a switching power supply that provides ±12 VDC to the rest of the modules in the chassis and +32 VDC to the Power Amplifier module if needed. The Assembly provides all transmitter control and monitoring functions.
350-Watt Digital VHF LB Transmitter pin diode circuit is connected to the output of the Upconverter Module, approximately +10 dBm in level, at J23, on the rear panel of the Driver/Amplifier Chassis Assembly. This output is cabled to the (A10) splitter and then the VHF amplifier tray in the system. 2.2.
350-Watt Digital VHF LB Transmitter is controlled by an external bias voltage that connects to the AGC Control Board and adjusts the AGC Pin Attenuator Bias Voltage which is applied to the Filter/Amplifier Board. The RF output of the Filter/Amplifier Board is amplified by the LB Amplifier Board and connected to the Overdrive Protection Board. The overdrive protection board provides a trip point, 110%, for over power conditions which will cut back the output power of the Tray.
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections Table 2-7: VHF Amplifier Tray Switches SWITCH FUNCTION Switches 220 VAC through a 15-amp circuit breaker-type CB1 protection device. The switch lights if AC is present. The On/Off Circuit Breaker AC is applied to the switching power supply in the tray.
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections Table 2-8: VHF Amplifier Tray Fault Indicators INDICATOR DESCRIPTION Indicates that the level of drive is too high. The protection DS1 circuit will limit the drive level to the set threshold. The fault Overdrive is generated on the overdrive protection board.
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections hold the IF Processor module in a mute state. Entering Standby Mode Operate Mode with Mute Condition Similar to the operate mode, the standby mode is entered various different ways. These are: The transmitter will remain in operate mode but will be placed in mute when the following fault conditions exists in the transmitter.
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections on the Controller Module. Since RF performance of the transmitter requires different hardware for different frequency bands, not all frequency configurations are valid for a specific transmitter. The Power detectors in the transmitter are frequency dependent, therefore the detectors of the power amplifiers are calibrated at their frequency of use.
350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance & Remote Control Connections module does not slide in easily, verify it is properly aligned in the nylon tracks, located on both the top and bottom of the module. 2.7: Customer Remote Connections The remote monitoring and operation of the transmitter is provided through jacks TB30 and TB31 located on the rear of the chassis assembly.
350-Watt Digital VHF LB Transmitter Signal Name Pin Designations RMT AUX IO 1 TB30-4 RMT RF System Interlock TB30-5 RMT Transmitter Operate RMT Transmitter Stand-By TB30-6 TB30-7 RMT Power Raise TB30-8 RMT Power Lower TB30-9 RMT System Reflect Power TB30-10 RMT System Forward Power TB30-11 RMT Spare 1 RMT Spare 2 TB30-13 TB30-14 Interlock Rtn TB30-15 +12 VDC TB30-16 Rtn TB30-17 -12 VDC TB30-18 Power Lower TB30-19 Rtn RTN Ground TB31-1,2,6-11 TB31-12 System Reflect Power TB31-
350-Watt Digital VHF LB Transmitter Signal Name Pin Designations Chapter 2, System Description, Maintenance & Remote Control Connections Signal Type/Description (Connects to triple peak detector board.) Analog Input - 0 to 1.00 V- This is the input of the “System TB31-14 Forward Power ” indicating the transmitter's Forward output power. The scale factor is 100 % / 0.80V.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Chapter 3 Installation and Setup Procedures There are special considerations that need to be taken into account before the DT325B 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.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure filtered to ensure that no airborne particulate of any kind will be carried into the transmitter. The combination of air conditioning for summer and ventilation during the cooler months is acceptable when the proper cooling cannot be obtained through the use of ventilation alone and using air conditioning throughout the year is not feasible. back of others.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure 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.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Figure 3-1: Typical 1 kW Minimum Ventilation Configuration Figure 3-2: Front and Rear View of the Driver/Amplifier Reconnection Drawing 3.2 Unpacking and Installation of the Cabinet and Trays cabinets to the shipping skids and slide the cabinet from the skid. Remove the plastic wrap and foam protection from around the cabinets.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure do not rub against each other and have no restrictions to free movement. Adjustments to the position of the trays may be necessary. To accomplish this, loosen the cabinet slide mounting bolts that hold the front of the slide to the mounting frame of the cabinet and move the tray up or down as needed to correct for the rubbing.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Figure 3-4: Rear View of Driver/Amplifier Chassis Assembly J40 J41 TB30 J21 TB31 J13 J68 J23 J10 J1 J32 J33 J34 Table 3-1: Rear Chassis Connections for the Digital Driver/Amplifier Chassis Assembly.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure 3.4 Setup and Operation Procedures as needed to attain a <5% reflected reading. The transmitter should initially be turned on with the RF output of the coaxial switch terminated into a dummy load of at least 350W. If a load is not available, check that the output is connected to the antenna.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure 3.4.1.1: Axciter Upconverter Sled Module LEDs on Front Panel DC OK - This illuminates Green when the DC outputs that connect to the modules in the transmitter are present. Status Indicators: 3.4.2: Front Panel LCD Screen for the Driver/Amplifier Chassis Assembly PLL: This illuminates Green when the phase lock loop circuit is closed, Red if unlocked.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Display Menu Screens for the Driver/Amplifier Chassis Assembly Table 3-2: Menu 01 - Splash Screen #1 This is the first of the two transmitter splash screens that is shown for the first few seconds after reset or after pushing the SPL button on the Main Screen. This screen will automatically switch to the second splash screen. Table 3-3: Menu 02- Splash Screen #2 This is the second of the two transmitter splash screens.
0-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Table 3-6: Menu 12 - Transmitter Device Data Access Screen This screen of the transmitter allows access to various parameters of the transmitter system. This is the entry point to Menu 30, the System Details Screens, by pausing the ENT button. When the ENT button is pushed, Menu 30 is accessed. Go to Menu 30, Table 3-11 for set up details.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Table 3-10: Menu 30-1 – System Details Screen This is first screen of the details screens. The ↓ and ↑ arrows allow you to scroll through the different parameters of each device as shown in Table 3-11. Each System Component is a different screen. The proper modules will be programmed for your system.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Menu 40 (Table 3-12) is entered by selecting ENT at Menu 13. Table 3-12: Menu 40 - Authorized Personnel Screen This screen of the transmitter notifies an operator that they are only to proceed if they are authorized to make changes to the transmitter's operation. Changes made within the following set-up screens can affect the transmitters output power level, output frequency, and the general behavior of the transmitter.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Table 3-14: Menu 40-2 - Transmitter Set-up: Model Select Screen This screen is used to specify which components are expected to be part of the system. By specifying the model number, the transmitter control firmware knows which components should be installed and it will be able to display faults for components that are not properly responding to system commands.
350-Watt Digital VHF LB Transmitter Chapter 3, Installation and Setup Procedure Table 3-19: Menu 40-13 - Transmitter Set-up: Minimum Forward Power Fault Threshold Screen This screen is used to set the minimum forward power fault threshold. When the transmitter is operating, it must operate above this value otherwise the system will shut down with fault for 5 minutes.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions Chapter 4 Circuit Descriptions NOTE: Information and drawings on the Axciter Modulator Tray, the Upconverter Module and the Downconverter Module are contained in the separate Axciter Manual. the AC Line #2 to the Fan. The other line of the split connects to J2. J1-2 is the earth ground input for the AC and connects to J3.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions PS6 protects the +12 VDC 2 Amp circuits for the Remote through J63 pins 17, 18, 19 and 20. If this circuit is operational, the Green LED DS6, mounted on the board, will be lit external watchdog IC (U2), a FET Q1 inverts the reset signal to a high that connects to the control lines of U5, an analog switch. The closed contacts of U5 connects the serial programming lines from J4 to U1. LED DS10 will be lit when programming port J4 is used.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions of the transmitter’s power amplifier are routed to the system power monitoring lines. enabled controller polls the U1 microcontroller on the same serial lines as a remote computer. The controller only gets data and sets conditions through the serial communications port. 4.1.2.2 Schematic Sheet 2 Digital output latch circuits are used to control system devices.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions second serial potentiometer is transferred through the first IC. The wiper position of the digital potentiometer circuit is used to set the gain of the op-amp. Lower digital values for the wiper settings increases the gain of the op-amp. If N=0 then Gain=6.0 and if N=255 then Gain=3.00. If the Vin=1.0 at spare_Ain_1 and N=128 then U21A out=4.0V with gain=4.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions that supplies the information from the selected source to the display. By pushing the button again, a different source is selected. This occurs for each push button. Refer to Chapter 3 for more information on the Display Menu Screens. 4.1.5 RF Output of Driver/Amplifier Chassis Assembly The RF output from the upconverter at the upconverter RF output jack J23, a BNC connector.
350-Watt Digital VHF LB Transmitter A2-A3 A3-A1, A3-A2 and A3-A3 A4-A1 A4-A2 & A4-A3 A5 A8 A10 Chapter 4, Circuit Descriptions 3-way splitter board (mounted in [A2] an RF enclosure assembly) Three low band VHF amplifier pallets (mounted in [A3] an RF enclosure assembly) 3-way combiner board (mounted on [A4] the 3 way combiner enclosure) Low pass filter board (mounted on [A4] the 3 way combiner enclosure) AGC control board Current metering board +30 VDC switching power supply assembly 1198-1608 P400-VHF-
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions The RF output of the filter/amplifier board connects to J2 of (A2) a RF enclosure that contains the VHF low band amplifier board, the overdrive protection board and the 3-way splitter board. to the comparator IC U1B. The trip point for the comparator is adjusted by R12, typically set to 110% output power.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions which are connected to J1, J2 and J3 on (A4-A1) a 3 Way Combiner Board (11981626). at J2 and J6-2 which produces the AGC output at J1 which connects to the automatic level control circuit on the Filter/Amplifier Board for the output power of the tray. 4.2.7 (A5-A1) 3 Way Combiner Board (1198-1626; Appendix D) The reflected power sample connects through J5 to a detector circuit consisting of CR13 and U5B.
350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions LEDs. This +12 VDC is supplied to the tray when the Driver/Amplifier is turned on. jumper from TB1-5 to TB1-6, to the Phase Shifter Board, the Filter/Amplifier Board and the Overdrive Protection Board. The Current Metering Board also supplies sample outputs of the operating currents of the amplifier devices in the Tray to the front panel Current Meter.
350-Watt Digital VHF LB Transmitter transmitter is switched to Operate. The Enable is applied to (A5) the AGC Control Board (1306482), which, if there is no Thermal Fault, connects the Enable from J10 Pins 6 & 7 to J1-18 & 14 on the Switching Power Supply Assembly. The Green Enable Front Panel LED (DS2) will light, indicating an Enable is present.
350-Watt Digital VHF LB Transmitter output of U2D is connected to J5-1, DC O/P 1. The second RF sample input enters the board at the RF I/P 2 SMA jack J2. Resistors R22, R17 and R23 form a 50O input impedance matching circuit. The sample is connected to a detector circuit made up of CR3, R24 C8, R42, and C9. For digital operation the jumpers, W2 on J6 and W5 on J9, are both between pins 1 & 2.
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures Chapter 5 Detailed Alignment Procedures 5.1 System Preparation place and make certain it connects to the backplane board. If the replacement module does not slide in easily, verify it is properly aligned in the nylon tracks, located on both the top and bottom of the module. After positioning, tighten the two grip lock connectors.
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures Remove the Sample Forward Power connection J4 from the board. The Output Power Level should drop to 20 % because of the VSWR Cutback and DS4 should light. The front panel Module Status LED should not be illuminated. RF Drive applied. To set the Bias, remove RF Drive and switch the front panel Current Meter to the ID position. Adjust the Bias Adjustment R4 on the Amplifier Board for 3 Amps on the meter.
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures 5.3.8 (A4-A1) 3 Way Combiner Board (1198-1626; Appendix D) Readjust R5 for 100 % on the Meter for 250 Watts Output. Switch the Tray Off and return the J6 and J7 Cables located on the 3 Way Combiner Board back to their original positions. Switch S1 located on the AGC Control Board to the AGC position, which is the normal operating position, after the set up is completed. There are no adjustments on this board. The three +51.
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures Main Screen. On the Axciter Upconverter Screen set AGC 1 to 1.5 Volts, by selecting 4 on the key board entry. This will cause a detail screen to appear prompting you to enter a number value. Monitor the AGC 1 Gain Value on the screen and increase or decrease the value of the number entered until the monitored reading is 1.5 Volts. 5.5.
350-Watt Digital VHF LB Transmitter Chapter 5, Detailed Alignment Procedures 5.5.3 Axciter Relay K2 Sample Values AGC Reference to the VHF Amplifier Tray and any readjustment may damage the tray. The K2 Relay is mounted on the Lower, Right Side of the Cabinet, accessed through the back. The RF Sample levels must be measured with a power meter before connecting them. Your installation may require RF attenuators to be placed in line with the samples to get them within the desired range. 5.6.
APPENDIX A DT325B SYSTEM SPECIFICATIONS
DT300B/DT400B Series DT334B/DT434B Pictured Low Power VHF DTV Transmitters/Translators 350W - 2.1kW These low power VHF DTV transmitters and translators deliver high quality and performance in a compact and economical package - perfect for broadcasters wishing to get a DTV signal on the air quickly. The time-proven Axcera DT1C modulator or optional DT2B adaptive modulator, generates the ATSC-compliant 8VSB IF signal, which feeds the companion upconverter.
DT300B/DT400B Series Low Power VHF DTV Transmitters/Translators 350W - 2.1kW Performance Options Frequency Range1 Low Band High Band 54 to 88 MHz 174 to 216 MHz Output Impedance 50 Ω Frequency Stability ±250Hz (Max 30 Day Variation) Regulation of RF Output Power 3% Out of Band -Compliant with FCC Mask2 Channel Edge ±500kHz 6MHz from Channel Edge -47 dB or better -110 dB or better Signal to Noise (SNR) 27 dB or better Data Interface Input Rate Input Interface 19.39 Mbps.
APPENDIX B SYSTEM DRAWINGS
350-Watt Digital VHF LB Transmitter Appendix B, System Drawings DT325B DT325B Transmitter w/Axciter Interconnect........................................... 1311143 Triple Peak Detector Board Schematic .......................................................................................... 1160522 DT325B, Rev.
APPENDIX C EXCITER/DRIVER CHASSIS ASSEMBLY DRAWINGS
350-Watt Digital VHF LB Transmitter Appendix C, Exciter/Driver Chassis Assembly Drawings Chassis Assembly, Exciter/Driver, LXB, 220 VAC Block Diagram .................................................................................... 1302139 Interconnect....................................................................................... 1310215 Backplane Board, Innovator LX Schematic ..........................................................................................
APPENDIX D VHF LOW BAND AMPLIFIER TRAY DRAWINGS
350-Watt Digital VHF LB Transmitter Appendix D, VHF LB Amplifier Tray Drawings VHF Low Band Amplifier Tray Block Diagram .................................................................................... 1304364 Interconnect....................................................................................... 1304365 Overdrive Protection Board Schematic ....................................................................................... 1198-3601 Phase Shifter Board Schematic .......................
350-Watt Digital VHF LB Transmitter Appendix D, VHF LB Amplifier Tray Drawings AGC Control Board Schematic .......................................................................................... 1306481 400 Watt VHF Amplifier Assembly (1304348) Delta RF Data Sheet ........................................................................P400-VHF-L DT325B, Rev.
