Transmitter Model Output Power Rating Amplifier Module Style Bias Protection Board 5721 2.
Bias Protection Board The RF power transistors contained in the amplifier module are supplied current and voltage through the bias protection board. The number of transistors contained in the amplifier module determines the size of the Bias Protection Boards as listed in the previous table. Logic circuitry on this board protects the transistors by shutting off power to the module in the event that the gate bias voltage is lost.
Test Points Description FWD DET LEV T/P Forward Power Detection Level Test Point provides a DC voltage that is proportional to the forward output power of the transmitter. (1V=100%) REFL DET LEV T/P Reflected Power Detection Level Point provides a DC voltage that is proportional to the reflected output power of the transmitter.
LO / Upconverter Module LO Sample - SMA connector RF Output - SMA connector Sample - SMA connector 34
This module consists of the A1, LO/ Upconverter board, a channel filter, and an output amplifier board. This module takes an external IF and converts it to the final RF output frequency using an internally generated local oscillator. The local oscillator consists of a VCO that is phase locked to an external 10 MHz reference. The 10 MHz reference and the VCO are both divided down to 500kHz and compared by the phase lock loop.
IF Processor Module The IF Processing module provides frequency response, group delay, and linearity equal ization for the transmission system. This module also monitors and controls the level of output power generated by the power amplifier. I/P - red LED indicates an input fault P/A - red LED indicates a PA fault (peak to ave) ALC - red LED indicates an ALC fault MUTE - red LED indicates loss of video or IF when in ALC Mode. Frequency Response Equalization - ALC -sets reference level of the ALC circuit.
The circuitry of the IF Processor Module goes through the following stages as described in the text that follows. Impedance Matching and Gain Selection Circuitry The IF input signal is applied from the backplane connection to J1-32B, the DIN connector located at the back of the module. An input impedance transformer can be set to 50Ω or 75Ω using jumper J28 and J29. The input range is selected with the I/P gain jumpers J8, J9, J10, and J11.
Input Signal Detection Circuitry A sample of the IF input signal that is taken through a directional coupler after passing through the impedance matching and gain circuitry, is applied to an envelope detector. The average and peak amplitudes of the envelope are measured and sent to a set of comparator circuits. These circuits will detect the following fault conditions if present.
Automatic Level Control Circuitry A voltage controlled attenuator placed after the frequency response equalization circuit allows dynamic adjustment of the IF signal gain and provides a means of controlling the level of output power generated by the power amplification stages of the system.
Group Delay Equalization Circuitry A set group of delay equalizer circuits can be inserted into the signal path after the ALC attenuator circuit. These have been designed for improved group delay performance for certain filtering and channel combining schemes. A description of these circuits are given below.
Linearity Equalization Circuitry After the filtering circuitry a linearity equalization circuit can be placed in the signal path to compensate for nonlinear distortions that may appear at a later stage in the transmission system. These distortions are the result of gain compression in high power amplifier stages. The linearity equalization circuit will offset gain compression by increasing signal gain through the module as the signal increases in power.
IF Processing Module Controls LED Indicators Description I/P Fault Illuminates when there is a loss of IF input signal P/A Fault Illuminates when the peak to average power ratio of the IF input signal exceeds the safety threshold.
Control and Monitoring Module The control and monitoring module interfaces with all other modules. Refer to the tables on the following pages for specific details about the functions of this module. ACTV - green LED that is dim during microprocessor boot up and bright when active.
IF Processor Module Interface Signal Name Backplane Outer loop Mon J19-11A Backplane Signal Type IF Processor Pin J20-26C Analog Input 0-1.25V Forward Power Metering J19-13A J20-23C Analog Input 0-1.25V Indicates the output power of the PA. Also referred to as the internal loop monitor, the factor of this input is 100% / V IF Processor Interlock J19-17A J20-12C Discrete contact closure input Provides a pull down to indicate that the IF processor module is installed.
Modulator Module Interface Signal Name Backplane Modulator Interlock J19-27B Backplane Modulator Pin J18-1C Unlock Mute J19-28B External IF present Video Loss Signal Type Description Discrete Contact Closure Input Provides a pull down to indicate that the modulator module is installed. A low level indicates the module is installed J18-1B Discrete Open Collector Input A low indicates the modulator PLL is unlocked.
Front Panel Interface Signal Name Backplane Fault Anode J19-1C Backplane Front Panel Pin J22-26 Fault Cathode J19-2C Operate Anode Signal Type Description Drive voltage to the fault LED Voltage is derived from the +5 supply which is passed through a resistor to supply the anode of the fault LED J22-25 Discrete open collector output Provides a pull down to turn on fault LED J19-3C J22-24 Drive voltage to the operate LED Voltage is derived from the +5 supply which is passed through a resisto
Control and Remote Interface Signal Name Backplane J19-29C Backplane Signal Type Control/Remote Pin J12-1 Discrete open collector input Standby CMD (FA) Low indicates FA requests the xmrt go to standby Operate CMD (FA) J19-30C J12-3 Discrete open collector input Low indicates FA requests the xmrt go to operate Aural / Visual Mute (FA) J19-31C J12-5 Discrete open collector input Low indicates FA requests an aural visual mute Visual Mute (FA) Ext Ref Present (FA) J19-32C J19-2B J12-3 J12-9 A
Frequency Generator /Upconverter Module Interface Signal Name Backplane External Ref Indicator J19-4A Backplane Signal Type U/C Pin J21-26C Discrete Open Collector Input Logic Enable J19-5A J21-25C Discrete CMOS Output Provides a load enable signal to PLL in the freq synthesizer chip. A transition from low to high loads data stored into synthesizer latches. Data J19-6A J21-24C Discrete CMOS Output Provides serial data to the freq synthesizer chip.
LCD Display Connections The LCD display assembly is located on the front panel behind the display. It interfaces with other devices through a ribbon cable.
INDEX/APPENDIX Typical Transmitter Site Typical 5720 transmitter site 2.5-2.
Troubleshooting Typical troubleshooting of the 5700 series entails module replecement, however some circumstances may require adjustments to the unit. Refer to the charts that follow for troubleshooting guidance.
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Material Return Procedure/Exchanges In order to efficiently handle equipment or components returned for repair or sent out on loan, Axcera requests that each returned item be accompanied by a Material Return Authorization Number (MRA#).
Proper Packing Of Materials When returning materials to Axcera, it is extremely important to pack them properly. Due to the delicate nature of components contained within the equipment, major damage can occur without proper packing. Please adhere to the following guidelines when returning materials. o Save the boxes that the transmitter is shipped in. Each tray is sent double boxed and enclosed in foam padding. Use the same packing method when returning materials.
LIMITED WARRANTY ONE YEAR Seller warrants each new product manufactured and sold by Seller against defects in material and workmanship under normal use and service, for a period of one (1) year from the date of shipment from Seller’s plant, when operated in accordance with Seller’s operating instructions. This warranty shall not apply to tubes, fuses, batteries, or bulbs.
WARNING!!! 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. 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.
ABBREVIATIONS/ACRONYMS A/D Analog to digital RF Radio Frequency AC Alternating Current SAW Surface Acoustic Wave AFC Automatic Frequency Control SNR Signal to Noise Ratio ALC Automatic Level Control USB Upper sideband AM Amplitude modulation VCXO Voltage Controlled Crystal Oscillator AGC Automatic Gain Control VSB Vestigial Sideband AWG American wire gauge VSWR Voltage Standing-wave Ratio BER Bit Error Rate BW Bandwidth DC Direct Current D/A Digital to analog dB Decibel
Index A M ABBREVIATIONS/ACRONYMS 60 Audio Jumpers 26 Automatic Level Control Circuitry 39 Material Return Procedure/Exchanges 56 Modulator Module 24 Modulator Module Interface 45 Module Replacement 21 B Backplane Board 22 Backplane Board Connections 23 Band Pass Filtering 40 Bias Protection Board 32 C Control and Monitoring Module 43 Control and Remote Interface 47 D Dip Switch Settings 25 Dual Power Detector 32 E EMERGENCY FIRST AID 59 English 11 External Amplifier 14 F Fault Condition 18 Frequency
