Nautel NX50 – 50kW AM Transmitter

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nautel_nx50

Features

Features

NX Advanced User Interface (AUI) The NX50 features a 17 inch color LCD screen with a wide range of configurable displays. The AUI can be controlled by touch screen, or via a mouse and keyboard.

  • Some of the features of the AUI include:
  • Real-time Impedance locus measurement
  • Instrument grade spectrum analyzer
  • IBOC modulation analyzer
  • Module level monitoring and control
  • Logging of all functions

Screens are easy to set up and read, and clearly display the parameters you need to see.

100% Remote Access

No matter where you are, you’re only moments away from ensuring your NX50 transmitter is operating optimally. Pull up a web browser, enter your transmitter’s IP address, and you’re connected. The complete local NX50 display functionality is available via the internet. Users can access status, controls, alarms, logs and reports.

Control Redundancy

The touch screen interface is implemented as a non-critical functional unit and may be completely removed from the system without affecting transmitter operation. The NX50 also supports SNMP and traditional direct wired contact closure capability for local or remote control.

Real-Time Impedance Measurement

The NX50 uses Nautel’s patent-pending real-time impedance measurement technology which compares the transmitted voltage and current waveforms to measure the load impedance over the operational frequency range. Because this system can measure impedance without requiring artificial swept tones, the antenna system impedance locus can be measured without taking the station off-air. Impedance is measured at the combiner so no correction for harmonic filter phase is required. This capability allows the antenna system load impedance can be optimized and monitored while the transmitter is operating normally.The NX50 also includes a built in directional coupler for spectrum measurement.Traditionally transmitters have utilized a voltage or current sensor. The directional coupler increases the accuracy of spectrum measurement into a real antenna load which is quite important when measuring adjacent channel emissions.

Class Leading Space Efficiency:

The NX50 is less than half the size of some comparable transmitters and is even 11 ft2 (1 m3) smaller than any other transmitter in its class. Yet even with such a compact footprint the NX50 offers easy and spacious access to all major serviceable components and modules.

On-Air Serviceability

NX50 transmitters are ruggedly engineered to provide easy on-air service and maintenance. In the NX50, 20 amplifiers combine to deliver up to 75 kW of average power (carrier plus modulation). At all power and modulation levels, all modules contribute equally to the final output. If an amplifier fails, no stress is imposed on the remaining modules and spectral integrity is never compromised. Maintenance can be performed whenever it is convenient. Generous ventilation is provided by redundant brushless DC ball bearing fans mounted in removable trays below the power modules. Airflow is unaffected by AC supply variations, further ensuring cool operation and long term reliability.

Automatic Standby

The most critical part of a transmitter is the exciter section, which provides the RF carrier and modulation control signals to the power modules. A unique feature of Nautel transmitters is the complete duplication of these circuits. Should a failure occur in the RF drive or modulator drive, the transmitter automatically switches over to the built-in standby exciter. This dramatically enhances the already high operational reliability inherent in the modular solid-state design.

Unattended Operation

The NX50 transmitter is built to stay on the air without human supervision. The NX50 was designed with a high VSWR threshold of 1.5:1 at rated power with 100% modulation. With more extreme VSWR values, power is automatically reduced to safe level. A unique circuit also dynamically stabilizes power against AC line voltage variations. After an AC power loss, over voltage or RF overload, prior operating status is automatically restored.

Powerful Building Block

The building block of the NX50 is an integrated RF amplifier/modulator with a carrier power capability of 2500W. These power modules plug into the front of the transmitter, making service easy. The Class-D RF amplifier uses four transistors that can be replaced without soldering using only a screw driver. Due to advances in amplifier technology, this amplifier is so efficient (96%) that it is capable of operating at over 10kW continuously. This power capability results in very low transistor junction temperatures assuring reliable operation even in the highest ambient temperatures.

Features

Redundant Architecture

Redundancy features and protection systems help you maintain operation without a site engineer, reducing your operating costs even further.

The NX50 offers:

  • Redundant Exciters
  • Redundant Modulators
  • Parallel/redundant fans
  • Redundant low voltage power supplies
  • Redundant amplifier control power supplies
  • Failsafe manual and remote control

Technical Specification

Technical Specification

Transmitter Type

  • Medium wave, AM, 100% solid state

Configuration

  • Twenty RF power modules, each including a single integrated RF amplifier/modulator
  • No frequency dependant parts in RF module
  • Each module is hot pluggable and has internal microcontroller for protection and monitoring over a serial bus
  • Short circuit protection at the module level offers an added layer of protection
  • Dual redundant digital single board exciters utilizing FPGA/DSP technology with automatic
  • changeover
  • Pre-correction utilized specifically to improve digital performance
  • Redundant low voltage power supplies

RF Output Power

  • Maximum: 75 kW RMS
  • Peak Power: 288kW
  • Carrier Power Range: Continuously adjustable from 0 to 55 kW in 100 W steps
  • Up to 62 preset levels, presets may include other operational parameters such as DRM vs Analog and different program inputs
  • Output level stabilized against AC supply voltage variations
  • Built in Dynamic Carrier Control
  • Built in AM stereo

RF Output Connection

  • 3 1/8 EIA female standard, other outputs on request

RF Output Impedance

  • 50 ohms, unbalanced

Efficiency

  • 90% typical at 50 kW

RF Load VSWR

  • 8000 peak reflected watts (1.5:1 VSWR @ 50 kW, 100% modulation) results in instantaneous power shutback
  • 2000 reflected watts RMS (1.5:1 VSWR @ 50 kW, 0% modulation) results in a graceful power reduction

Frequency Range

  • 531 kHz to 1,620 kHz.
  • “Quick frequency change capability”

Frequency Stability

  • ±2 ppm over temperature range
  • Optional 300 ppb ovenized source with GPS option

Modulation Type

  • 6 phase direct digital modulation
  • 1.8 MHz modulation sample rate

Modulation Capability

  • 140% positive peak modulation to 50 kW
  • 130% positive peak modulation to 55 kW

Spurious and Harmonic

  • 80 dB or more below carrier at 50 kW
  • Meets ITU-R SM.328-10
  • Meets ITU-R SM.329-9

 

AC INPUT

 

Voltage

  • 340 V to 510 V, 3 phase or to customer specifications

Power Supply Variation

  • ±10% voltage, 47 Hz to 63 Hz*

Power Consumption

  • 55.5 kW typical at 50 kW, 0% modulation
  • 85 kW typical at 50 kW, 100% modulation
  • Cos (theta)
  • 0.95 typical

 

ENVIRONMENTAL

 

Temperature Range

  • 0°C to + 50°C
  • Derate 3°C per 500 m above sea level (2°C per 1,000 ft)

Humidity Range

  • 0% to 95% non-condensing

Altitude

  • 0 m to 4,000 m (0 ft to 13,000 ft)

Cooling Air Requirements

  • 2,550 m3/hr (1,500 CFM)

SAFETY

  • Meets EN60215: 1976 Safety Requirements for Radio Transmitting Equipment

 

PHYSICAL

 

Dimensions

  • 184.2 cm H x 95.7 cm W x 120 cm D
  • (72.4″ H x 37.7″ W x 47.2″ D)

Weight

  • Main transmitter cabinet with modules installed: 567 kg (1250 lbs)
  • Power transformer (In transmitter Cabinet): 417 kg (919 lbs)

 

AUDIO PERFORMANCE

 

Analog Broadcast Inputs

  • Dual AES-EBU Digital Audio inputs* adjustable from -30dBFS to 0dBFS for 100% modulation
  • 600 ohms balanced analog audio input +10 dBm nominal for 100% modulation, adjustable from -10 to +12 dBm

Digital Broadcasting Inputs

  • I,Q over AES-EBU, SRC available* with sample rate converter
  • I,Q over LVDS, 3 pairs, Clock, Data, frame sync
  • *Two AES-EBU inputs provided and may be used for either analog audio or digital I,Q inputs
  • Optional Embedded DRM Generator/Content Server
  • Optional HD Radio Generator (Exgine™)

Frequency Response

  • +0.2 dB/-0.8 dB, 30 Hz to 10,000 Hz.
  • Optional audio input filters available to meet regional bandwidth restrictions

Total Harmonic Distortion

  • Better than 0.8% (THD), 30 Hz to 10,000 Hz at 95% modulation (typical)

Intermodulation Distortion

  • SMPTE 1:1 Ratio, 60Hz/7kHz, 95% Mod Peak – 0.5% @ 50kW (typical)
  • DIM-B, 2.96kHz/9kHz, 80% Mod Peak – 0.5% @ 50kW

Carrier Shift

  • 0.5% or less

Hum and Noise

  • -65 dB or better below 50kW, 100% modulation

 

CONTROL AND MONITORING

  • Extensive Control/Monitoring/Troubleshooting system through 17″ front panel LCD touchscreen. Touch panel control system is non-critical and may be removed from the system without affecting transmitter operation or remote control/monitor via direct wired connections. Redundant back-up control interface provides control in case of front panel computer system failure. Built in instrumentation providing detailed spectrum/impedance and modulation analysis.

 

Metering

  • Cube
  • DC Voltages (B+, PA and 15V)
  • DC Current
  • Sample Levels (PDM and RF Drive)
  • Fan Speeds
  • Heat Sink Temperature
  • Rack
  • DC Voltage levels (15V, 5V, 30V, 48Vand B+)
  • Rectifier Fan Speeds
  • DC Current
  • Rectifier Heat Sink Temperature
  • AC Voltage
  • Exciter
  • Output Current (RMS, Peak, Carrier)
  • Output Voltage (RMS, Peak, Carrier)
  • Forward Power (RMS, Peak, Carrier)
  • Reflected Power (RMS, Peak, Carrier)
  • Audio/Modulation Levels (RMS and Peak – Positive/Negative)
  • Load Impedance
  • Controller
  • PDM and RF Drive Levels
  • Ambient Temp

RF Monitor

  • RF monitor is a power sample (using a directional coupler) that will allow for accurate audio performance measurements

Status

  • Easy access to current transmitter operating state, past and present alarm conditions and historical trends of both digital and analog channels

Schedule

  • Intuitive easy to read built in scheduler
  • Up to 144 yearly rules can be defined by user

Remote Control/ Monitoring

Three Remote interfaces:

  • Direct wired optically isolated inputs and open collector outputs
  • Web interface – All locally available control is available over TCP/IP web interface
  • SNMP

 

Notes: Specifications defined in a laboratory environment with high grade source and demodulation equipment. Standard factory measurements does not include all items.

 

 

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