Harris Platinum HT EL 2000LS Technical Manual

Harris Platinum HT EL 2000LS Technical Manual Manual pdf 49 page image

5.6.2 Visual Peak-sync to Average Power Conver-sion FormulasMeasurement of RF power has historically been done usingdirectional couplers with diode detecting elements that can becalibrated against calorimetric standards. This allows the meas-urement of average RF power. TV transmission systems arerated in peak power, referred to as peak-sync or sync peakpower. The ratio between peak and average power is easilycalculated if the moduletion is simple, consisting only of sync.The formula is shown in Table 5-1.Table 5-1 includes the results of typical calculations.Use values from Table 5-1 or independent calculations in thefollowing power calibrations.5.7 Transmitter Metering and ControlCalibrationMeter board calibration (located in the exciter)Each function on the Digital Display and Bar Graph is individu-ally calibrated as follows:5.7.1 Power Supply Meter Calibration5.7.1.1 PS VOLTS Calibration:a. On the Interface Logic Board connect a Digital Voltmeter(DVM) to 1A3TP10 (50 V Supply Voltage Sample) andGround.b. Turn on the Transmitter. The DVM should read 1.75+/-0.25 volts at 1A7TP10 for a supply voltage of 50 VDC.c. Select PS VOLTS on the Exciter Meter.d. On the Exciter Meter set R1 (PA V CAL) for 50% on theBar Graph, 10 segments illuminated.e. Adjust R95 (PA V CAL) for and indication of 50.0 on theDigital Display.5.7.1.2 PS CURRENT CalibrationThis is factory adjusted. Use a precision current shunt and meterif recalibaration is needed.a. Select PS CURRENT on the Exciter Meter.b. On the Exciter Meter set R2 (PA I CAL) to match themeasured current on the Bar Graph. The Bar Graph reads120 A full scale (20 segments).c. Adjust R94 (PA I CAL) for numeric indication the sameas the measured current.5.7.2 Exciter RF Output Meter Calibration5.7.2.1 Exciter Visual Power Calibrationa. Connect an RMS low power wattmeter to 1A8J2 (VIS RFOUT).b. Using black picture power operating conditions, adjustvision exciter power output to the average value deter-mined in paragraph 5.6.2.c. Select EXC VIS on the Exciter Meter.d. On the Exciter set R3 (EXC VIS CAL) for full scale onthe Bar Graph.e. Adjust R97 (EXC VIS CAL) for a numeric indication of1.000 watts.5.7.2.2 Exciter Aural Power Calibrationa. Connect an RMS low power wattmeter to 1A8J3 (AURRF OUT).b. Adjust the aural power to 1.00 watts on the power meter.c. Select EXC AUR on the Exciter Meter.d. On the Exciter set R4 (EXC AUR CAL) for full scale onthe Bar Graph.e. Adjust R96 (EXC AUR CAL) for a numeric indication of1.000 watts.5.7.3 Transmitter RF Output Meter CalibrationInitial Setup for Calibration:Preset the following Jumpers:Jumper PositionJP1 Visual Foldback 2-3JP2 Aural Foldback 2-3JP3 Aural AGC 2-3JP12 Visual AGC 2-3JP16 High VSWR Shutdown 2-3The transmitter must be operational with visual and aural con-nected to a calibrated load and wattmeter. The visual modulatedwith a black picture, 40 units of sync.Table 5-1. Peak to Average RatioSection V - Maintenance888-2457-001 5-3WARNING: Disconnect primary power prior to servicing.