Nautel XR12 Operation And Maintenance Manual

Also see for XR12: Installation manual Troubleshooting manual Preinstallation manual

XR12 Operations and Maintenance Manual DescriptionPage 1-4 Issue 3.1 2013-03-14Interphase PDM Driver PWBsThe interphase PDM driver PWBs (A2A3 and A2A5) generate the required interphase PDM drivesignals for the modulator assemblies in the RF power modules. These PDM drive signals determinethe transmitter output power level as well as the output modulation level.The Carrier Ref input is applied from the control/display PWB, via the exciter interface PWB, todetermine the output power of the transmitter. A sample of the B+ supply voltage is applied to thecarrier level control circuit which is designed to hold the transmitter output power constant withvariations in the unregulated B+ supply. An inhibit PDM input is applied from the control/displayPWB to inhibit the interphase PDM drive during a system during alarm/fault conditions. A resetinput provides a reset pulse to reset protection circuits internal to the interphase PDM driver PWB.RF drive buffer PWBThe RF drive buffer PWB (A24) buffers the carrier frequency signal Fc, generated by the active RFsynthesizer PWB (A or B), to provide the RF drive voltages to the RF power stage. The buffered Fcsignal is then applied to the transmitter’s RF power stage.RF power stageSee electrical schematic SD-3. The RF power stage includes the RF power blocks.Each RF power block contains an RF power module, fan tray, relay, and connections to thedistribution PWB. Each RF power module accepts RF drive and control voltages from the exciter andRF drive stages. B+ and +24 V dc voltages are input from the B+ distribution PWB and the +24 Vdc supply in the RF power stage. The outputs of the RF power modules are applied to the RFcombiner/output filter stage.RF power module reset to the RF power stage originates in the control/monitor stage. RF powermonitoring and RF power stage status information are applied to the control/monitor function.