Nautel NX5 AM Manual

3: OPERATION & MAINTENANCE
MANUAL
NX5 AM
TRANSMITTER
Document ID: NHB-NX05-OPS
Version: 0.1
Issue Date: 2015-08-01
Status: Preliminary

VERSION 0.1 2015-08-01 PAGE III
NX5 OPERATION & MAINTENANCE MANUAL
Contact Information
Nautel Limited
10089 Peggy’s Cove Road
Hackett’s Cove, NS Canada B3Z 3J4
Toll Free: +1.877.6NAUTEL (662.8835)
(Canada & USA only) or
Phone: [phone] or
Fax: [phone]
Nautel Inc.
201 Target Industrial Circle
Bangor, Maine USA 04401
Phone: [phone]
Fax: [phone]
Customer Service (24-hour support)
+1.877.628.8353 (Canada & USA only)
+1.902.823.5100 (International)
Email: [email protected]
Web: www.nautel.com
The comparisons and other information provided in this document have
been prepared in good faith based on publicly available information.
For verification of materials, the reader is encouraged to consult the
respective manufacturer's most recent publication on the official
website or through contact with Customer Service.
© Copyright 2015 NAUTEL. All rights reserved.

NX5 OPERATION & MAINTENANCE MANUAL TABLE OF CONTENTS
VERSION 0.1 2015-08-01 PAGE 3.V
CONTENTS
Contact Information 3.1.iii
Release Control Record vii
Description 3.1.1
Ac-Dc Power Stage 3.1.2
Exciter Stage 3.1.3
Control/Monitor Stage 3.1.5
RF Power Stage 3.1.7
RF Output Network 3.1.8
Operating the Transmitter 3.2.1
User Interface Options 3.2.4
Viewing Transmitter Log 3.2.22
Viewing Instrument Panels 3.2.31
Available Instrument Panels 3.2.35
Viewing Real-Time Meters 3.2.48
Presets - Editing Operational Settings 3.2.58
Resetting Alarms 3.2.84
Viewing Transmitter Status - Remote AUI 3.2.85
User Settings 3.2.87
User Settings - Front Panel UI 3.2.111
Precorrection Settings 3.2.114
User Accounts 3.2.123
System Settings - Remote AUI 3.2.127
System Settings - Front Panel UI 3.2.134
Factory Settings 3.2.147
Configuring Remote Inputs and Outputs 3.2.163
Preset Scheduler 3.2.173

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Audio Player 3.2.176
Changing Exciter Transfer Settings 3.2.182
Routine maintenance 3.3.1
Upgrading Software 3.3.1
Scheduled Maintenance 3.3.5
Replacing the Air Filter 3.3.6
Performing On-Air Checks 3.3.8
Replacing the Control/Interface PWB Battery 3.3.9
Inspecting Lightning Protection Systems 3.3.11
List of terms 3.4.1

NX5 OPERATION & MAINTENANCE MANUAL
VERSION 0.1 2015-08-01 PAGE 3.VII
Release Control Record
ISSUE DATE REASON
0.1 2015-08-01 Initial Release of manual. Supports NX5 hardware NARA66.
Supports NX SW version 4.5 and higher.

NX5 OPERATION & MAINTENANCE MANUAL
PAGE 3.VIII VERSION 0.1 2015-08-01

NX5 OPERATION & MAINTENANCE MANUAL DESCRIPTION
VERSION 0.1 2015-08-01 PAGE 3.1.1
SECTION 3.1: DESCRIPTION
This section provides a high-level description of the transmitter’s key sections. The transmitter circuitry
is subdivided into five basic stages.
Ac-Dc Power Stage
Exciter Stage - see page 3.1.3
Control/Monitor Stage - see page 3.1.5
RF Power Stage - see page 3.1.7
RF Output Network - see page 3.1.8 (includes combiner and filter)
Refer to the functional block diagram: Figure 3.1.5 on page 3.1.13.
NX5 Electrical Schematics
Some descriptions in this section refer to electrical schematics (SD-#s) . These are located at the end of
the NX5 Troubleshooting Manual .
Redundancy
The NX5 features redundancy in the following key systems:
Exciters (optional)
RF power modules
Cooling fans

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PAGE 3.1.2 VERSION 0.1 2015-08-01
Ac-Dc Power Stage
See Figure 3.1.5 on page 3.1.13 and electrical schematic SD-1. The ac/dc power supply stage contains
the input power transformer that receives the main ac input to the transmitter. It also contains the
transmitter’s low voltage power supplies and rack interface PWB. The ac/dc power supply stage also
includes a three-phase SCR rectifier assembly, B+ current sensor, B+ distribution assembly and arc
detector assembly.
Ac Power Transformer
The NX5’s power transformer can be set to use a range of input voltages. See Section 2.4, “Connecting
Ac Power” on page 2.4.1 in the NX5 Installation Manual .
High Voltage B+ Supply
The secondary of the power transformer is applied to the SCR rectifier assembly to create the
transmitter’s B+ voltage. The output of the rectifier assembly is fed through the B+ current sensor,
which supplies a B+ current sample to the rack interface PWB. The rectifier assembly output is applied
to a choke input filter and the B+ distribution assembly, which then provides the B+ voltage to the RF
power modules.
The B+ discharge relay, which is part of the B+ distribution assembly, opens when ac power is applied
and closes and ac power is removed, applying a high power discharge resistor across the B+ bus to
quickly discharge the voltage. When the discharge relay closes, a microswitch ensures the SCR rectifier
is immediately inhibited.
Low Voltage Power Supplies
One phase of the power transformer’s secondary is also used to provide a source for the low voltage dc
power supplies and an ac sample for the rack interface PWB. The low voltage power supply outputs
(+48 V and +15 V) are distributed throughout the transmitter via the rack interface PWB. The +48 V
power supply sources the transmitter’s cooling fans. An inhibit signal, controlled by the rack interface
PWB, is applied to the +48 V power supply to turn the fans on and off. The +15 V power supply sources
all of the low voltage control circuitry.

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VERSION 0.1 2015-08-01 PAGE 3.1.3
Rack Interface PWB
The rack interface PWB provides various functions for the ac-dc power stage, including:
Monitors the B+ voltage and regulates the SCR rectifier’s output via the B+ level control
signal applied to the rectifier’s SCR control board.
Monitors the SCR rectifier’s temperature and phase loss indication and provides this
information, along with data received over a serial bus from the RF power modules, to the
transmitter controller.
Uses the Fast Shutback signal, if necessary, to request a transmitter shutback.
Monitors the arc detector assembly.
Generates the +30 V dc supply used by the SCR rectifier’s controller and the -15 V dc supply
used by the Hall Effect B+ current sensor
Accepts the RF drive signals from the control/interface PWB and distributes them to the power
module interface PWB.
Exciter Stage
See 3.1.1 on page 3.1.4, Figure 3.1.5 on page 3.1.13 and electrical schematic SD-2. The exciter stage
consists of digital AM exciter PWBs A (A5) and B (A6, optional) and control/interface PWB (A4). The
dual digital AM exciter PWBs provide two independent exciter sections (A and B), which can be
selected automatically or by local or remote control. The control/interface PWB acts as an interface
point for audio inputs and RF drive and PDM outputs.
Digital AM Exciter PWB(s)
The digital AM exciter PWBs [A (A5) and B (A6, optional)] accept audio signals for analog modulation,
I/Q over AES signals for DRM modulation, audio data over I2S from the audio player and IBOC signals
over I2Sfrom an integrated Exgine card, and generate fully digital RF drive and interphase PDM drive
signals for the power amplifiers and modulators in the RF power modules.
Audio signals for analog AM modulation can be applied as balanced analog (600 ohm impedance) or
digital (AES/EBU format). All audio inputs are digitized and sample rate converted. A DSP provides
initial data conditioning, including the initial filtering and interpolation of incoming audio or digital
radio data.
An FPGA generates the digital PDM signals and synthesizes the carrier frequency RF drive signal. It also
performs digital up-conversion, reverse path demodulation and downconversion and B+ voltage
compensation.

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Figure 3.1.1: Exciter Stage
The digital PDM component consists of six phased PDM signals, each separated by 60 electrical
degrees. These PDM drive signals determine the transmitter output power level as well as the output
modulation level. Three of these phases, each separated by 120 electrical degrees (e.g., 1, 3 and 5), are
applied to a given RF power module. To achieve optimal harmonic cancellation, three different phases
(e.g., 2, 4 and 6) are applied to the adjacent module.
Samples of the RF output voltage, RF output current, SCR rectifier temperature and RF power module
temperature are monitored. If a parameter exceeds an acceptable limit, the active exciter attempts to
compensate by decreasing its output power to restore the parameter to an acceptable level.
A sample of the B+ supply voltage is monitored. A B+ compensation circuit adjusts the PDM duty cycle
to compensate for variations in the B+ supply in order to maintain constant transmitter output power
and mimimize hum.
A PDM inhibit (A or B) input is applied from the control/interface PWB to inhibit the PDM drive for a
specific exciter during certain alarm/fault conditions.
RF Drive Distribution
The control/interface PWB (A4) accepts the RF drive (+ and -) signals from the digital AM exciter PWBs
(A and B) and buffers the individual RF drive 1 and 2 outputs that are provided to the rack interface
PWB.
Digital AM
Exciter A
+15 V dc
-15 V dc
+5 V dc
Analog/
Digital
Modulation
Inputs
Digital AM
Exciter B
Control/Interface
Analog/
Digital
Modulation
Inputs
Control/Interface
RF Drive (A)
RF Drive (B)
PDM (A)
PDM (B)
RF Drive 1
RF Drive 2
PDM 2/4/6
To RF Power Modules
PDM 1/3/5

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.
Accepts +15 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.

NX5 OPERATION & MAINTENANCE MANUAL DESCRIPTION
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Accepts customer D-sub connections for digital remote inputs, digital remote outputs and
analog outputs.
Accepts customer connections to complete the external interlock and transmitter (PDM)
inhibit circuits.
Accepts customer Ethernet connection to allow access to the transmitter’s remote AUI feature.
Accepts customer USB connections for audio playlist.
Contains a microcontroller that: manages presets, scheduler and exciter changeover; controls
RF on/off status, controls RF symmetry, controls RF monitor level, stores network settings;
manages the transmitter’s response to certain alarm/fault conditions.
Contains a CPLD that: performs basic logic operations on logic inputs to produce logic
outputs; latches off RF drive during certain alarm/fault conditions; routes program inputs and
synchronization signal to the exciter(s); muliplexes exciter A and B’s PDM outputs.
Contains an ARM processor (host)that: runs the operating system and server that provides
remote AUI functionality; accepts USB and Ethernet inputs.
Local and Remote Interfacing
The transmitter’s local interface is provided via the front panel UI display (U3) - a 4 x 20 graphic LCD
display - and its adjacent keypad. The front panel UI contains a menu-based series of pages that serve
specific functions. Similar interfacing, as well as more advanced functionality, is available on a remotely
accessed AUI. The AUI is a flash graphic that can be accessed via an Ethernet connection on any web-
based PC or handheld device.
The UI interface PWB (A3) provides an interface between the front panel display (U3) and the control/
interface PWB (A4). It also contains the pushbutton switches (RF ON, RF OFF and LOCAL/REMOTE)
and associated status LEDs that protrude through the front panel, below the UI.

NX5 OPERATION & MAINTENANCE MANUAL DESCRIPTION
VERSION 0.1 2015-08-01 PAGE 3.1.7
RF Power Stage
See Figure 3.1.5 on page 3.1.13 and electrical schematic SD-4. The RF power stage contains two RF
power modules (A12 and A13) two fan tray assemblies (A16 and A17), power module interface PWB
(A10), rack interface PWB (A9) and RF combiner transformer (A21).
Each RF power module accepts RF drive from the rack interface PWB through the power module
interface PWB and PDM from the exciter stage. B+ and +15 V dc voltages are applied to the RF power
modules via the B+ distribution assembly, the rack interface PWB and power module interface PWB.
+48 V dc voltage is applied to the fan trays via the rack interface PWB and the power module interface
PWB. The output of each RF power module is applied to a primary winding of a series combining
transformer. The resultant combined output is applied to the RF output network.
Each RF power module also:
monitors the tachometer signals from the two fans on its associated fan tray - applied through
the power module interface PWBs - and will shut down if one of the fans fail.
controls its associated RF relay on the power module interface PWB, ensuring the relay is
closed when the RF power module is disabled, allowing combiner current to continue flowing
in the primary of its associated combiner transformer.
provides status information to the rack interface PWB over a serial bus connection.

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RF Output Network
See Figure 3.1.2, Figure 3.1.5 on page 3.1.13 and electrical schematic SD-5. The combined RF output is
filtered through an RF network consisting of two “T” networks with a shunt third harmonic trap, and
then provided to the antenna system. The RF output is monitored by an RF current probe, RF voltage
probe and directional coupler. Samples from these probes are provided for control and monitoring
purposes (see “VSWR Protection” on page 3.1.9). A static drain choke provides a dc short to ground to
dissipate static build-up on the antenna system, and an adjustable spark gap provides protection for
the transmnitter output from lightning events on the antenna.
Figure 3.1.2: RF Output Network
RF Pwr Mdl 1
RF 1 (+)
A23 Directional Coupler
Forward Power
RF Current Sample
RF 1 (-)
L
Shunt Capacitor Bank
A22 Static Drain
E1 Spark gap
RF Out
to Antenna
LL
Series Combining Transformer
Shunt Capacitor Bank
Sample
Reflected Power
Sample
Part of A20 - Current Probe
RF Pwr Mdl 2
RF 2 (+)
RF 2 (-)
Part of A20
Voltage Probe
L
C
Surge Arrestor
RF Voltage Sample

NX5 OPERATION & MAINTENANCE MANUAL DESCRIPTION
VERSION 0.1 2015-08-01 PAGE 3.1.9
VSWR Protection
The transmitter uses an advanced DSP based VSWR protection system. Circuitry in the RF output
network (see 3.1.2 on page 3.1.8) samples the RF voltage and RF current at the input to the harmonic
filter. These current (I) and voltage (V) samples are applied to ADCs on the digital AM exciter PWBs. The
digitized I and V signals are used to calculate the impedance (Z) at the combiner output. An FPGA
performs high-speed calculations, so there is minimal response delay.
There are several types of VSWR protection, which continuously operate:
Peak Reflected Power from Directional Coupler
Fast VSWR protection is used to detect transient faults when the reflected power quickly increases due
to arcing, lightning or short circuits. The protection circuit is set at 1.5:1 at 5 kW plus 100% peak
modulation using the reflected power sample from the directional coupler (see 3.1.2 on page 3.1.8) and
triggers the controller’s Fast SWR Shutback alarm, designed to shutback PDM (reduce power to zero)
and disable RF drive in less than 100 ns. This protection ensures that the RF drive to the RF power
modules is disabled in less than one RF carrier period, preventing the amplifier from operating into a
potentially harmful load.
Calculated Reflected Power from I and V Samples
The peak reflected power calculated by the FPGA is supplimentary to the fast SWR protection, allowing
the exciter to detect and control the repsonse to the event. The peak reflected power limit - based on a
VSWR of 1.5:1 at rated power plus 100% peak modulation - is 16 % of the ransmitter’s rated power
(i.e., 800 W). If this limit is exceeded, the transmitter’s output power instantly reduces to 0 W. This
triggers the exciter’s SWR Shutback alarm.

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Shutback:
Shutbacks can be caused by the following alarms: SWR Shutback (exciter), Fast SWR Shutback
(controller), Over-Current Shutback (exciter), Over-Voltage Shutback (exciter) and Arc Shutback
(controller).
During a single shutback event (see 3.1.3 on page 3.1.10), the transmitter reduces the output
power to 0 W, and remains in that state for 100 ms. This allows time for an arc or transient
fault to clear. After 100 ms, the output power exponentially ramps up (to the power set point
or the power limit set by the exciter, whichever is lower).
After 30 s, the transmitter returns to full power under control of the normal ALC. When a
shutback occurs, the cutback accumulator is set to a normalized value of 1. This value decays
at a rate of 1/60 of a second (0.0167 s) so after 60 s, the accumulator value returns to 0 and
the shutback event is no longer in memory.
Figure 3.1.3: Shutback Event

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VERSION 0.1 2015-08-01 PAGE 3.1.11
Cutback:
A cutback occurs after multiple shutback events. When three shutback events occur within a 15 s
period, the cutback accumulator exceeds its threshold. The transmitter responds by limiting the output
power to 85% of the previous power set point or the power at which the shutback event occurred,
whichever is lower. When multiple cutback events occur, the output power is reduced by 85% of the
current level after each event. The minimum cutback power level is 2% of full carrier power. Further
cutbacks will not decrease the power beyond this point. When the transmitter is recovering from a
cutback event, the accumulator must first reach 0, which takes 60 s. After that, transmitter power is
gradually restored to full power according to the curve shown in 3.1.4 on page 3.1.11.
Figure 3.1.4: Cutback Recovery Time

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Average Reflected Power Foldback
If the average reflected power, calculated over a nominal 5 s period, exceeds a limit of 4% of rated
power, the output power is gradually reduced in order to maintain a reflected power that is less than
this limit. This gradual reduction in power into high VSWR allows the transmitter to continue to operate
into VSWR levels as high as 1.5:1 at full carrier power and even higher VSWR levels when the carrier
power is reduced. This VSWR protection is intended to protect against short or open circuits when the
transmitter is turned on, as well as non-transient faults such as a poorly tuned antenna system.