Nautel XR6, Operation And Maintenance Manual

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XR6/XR3 Operations and Maintenance Manual Description
Page 1-4 Issue 3.1 2013-03-14
Interphase PDM Driver PWBs
The interphase PDM driver PWBs (A2A3 and A2A5) generate the required interphase PDM drive
signals for the modulator assemblies in the RF power modules. These PDM drive signals determine
the 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, to
determine the output power of the transmitter. A sample of the B+ supply voltage is applied to the
carrier level control circuit which is designed to hold the transmitter output power constant with
variations in the unregulated B+ supply. An inhibit PDM input is applied from the control/display
PWB to inhibit the interphase PDM drive during a system during alarm/fault conditions. A reset
input provides a reset pulse to reset protection circuits internal to the interphase PDM driver PWB.
RF drive buffer PWB
The RF drive buffer PWB (A15) buffers the carrier frequency signal F
c
, generated by the active RF
synthesizer PWB (A or B), to provide the RF drive voltages to the RF power stage. The buffered F
c
signal is then applied to the transmitter’s RF power stage.
The RF drive buffer PWB also serves as an input for the
Phase
signal when IBOC operation is
selected (the
Mag
signal goes to the remote interface PWB).
RF power stage
See 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 the
distribution PWB. Each RF power module accepts RF drive and control voltages from the exciter and
RF drive stages. B+ and +24 V dc voltages are input from the B+ distribution PWB and the +24 V
dc supply in the RF power stage. The outputs of the RF power modules are applied to the RF
combiner/output filter stage.
RF power module reset to the RF power stage originates in the control/monitor stage. RF power
monitoring and RF power stage status information are applied to the control/monitor function.