Nautel NX5 AM, Operation & Maintenance Manual

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NX5 OPERATION & MAINTENANCE MANUAL DESCRIPTION
VERSION 0.1 2015-08-01 PAGE 3.1.5
PDM Distribution
The control/interface PWB (A4) accepts the six PDM (1, 2, 4, 5, 7 and 8) signals from the digital AM
exciter PWBs (A and B) and splits the active exciter PDM signals into two (+ and -) differential outputs
that are provided to the RF power stage.
Other Functions
The exciter stage interfaces with the transmitter controller to perform various other functions, including:
 Provides an RF Drive Latch signal to the transmitter controller to inhibit the RF drive for a set
period of time during specific alarm/fault conditions.
 Provides a PM Enable signal for the RF power modules to monitor the PDM cable status. This
signal is held “low” (0 V) by the exciter.
 Provides real-time telemetry of exciter samples over a streaming bus to the transmitter
controller for use by various instruments on the remote AUI such as the spectrum analyzer,
Smith chart, signal constellation, audio levels, etc.
 Accepts 10 MHz, 1 PPS and 1 kHz synchronization signals from the selected source (Ext 10
MHz, GPS Sync PWB or Combiner) for synchronizing the RF carrier frequency and phase.
Control/Monitor Stage
See Figure 3.1.5 on page 3.1.13 and electrical schematics SD-2 and SD-3 .
The control/monitor stage monitors critical signal samples and status/alarm signals from the exciter
stage, RF power stage, and ac/dc power stage. It also provides customer interfaces for monitoring
transmitter status and accepts customer inputs for distribution to other system components. The
control/interface PWB (A4) is the primary component of the control/monitor stage. It provides various
functions, including:
 Accepts all analog and digital modulation inputs and synchronization signals (10 MHz, 1 PPS,
1 kHz) and distributes them, along with RF voltage and current samples, to the exciter stage.
 A15 V from the rack interface to generate on-board power supply requirements.
 Monitors the forward and reflected power samples from the directional coupler and initiates a
shutback when the reflected power exceeds the factory set threshold.
 Amplifies the forward and reflected power samples for the RF monitor output.
 Monitors shutback requests from the rack interface for arc detector and low B+ shutdown
events.