Nautel NX15 – 15kW AM Transmitter

Nautel logo



The NX15 stands apart compared to other 15kW AM transmitters on the market today with efficiency of 86%, compact enclosures that are 1/3 to 1/4 smaller, and digital transmission capability.

Front panel control of the new NX15 transmitter is via an easy-to-use LCD display. Like other members of the NX Series, it also includes Nautel’s award-winning Advanced User Interface (AUI). Log in to the AUI on the NX15 using a web browser on your PC or mobile device to gain access to unprecedented instrumentation and control whether you are at the transmitter site, the office or home.



AUI’s functionality includes built-in commercial grade instrumentation, full remote access; SNMP support; an instrument-grade spectrum analyzer and network analyzer; real-time modulation error ratio measurement; monitoring and control including event logging; email and SMS notifications; backup audio via streaming and USB playout; presets and enhanced support services including Nautel Phone Home.

Analog, DRM and HD Radio models are available.

Technical Specification

Technical Specification

Transmitter Type

  • Medium wave, AM, 100% solid state



  • Ten 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: 22.5 kW RMS
  • Carrier Power Range: 0 to 16.5 kW
  • 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



  • 84% typical at 15 kW



  • 4000 peak reflected watts (1.7:1 VSWR @ 15 kW, 100% modulation) results in instantaneous power shutback
  • 1000 reflected watts RMS (1.7:1 VSWR @ 15 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
  • 8 MHz modulation sample rate


Modulation Capability

  • 140% positive peak modulation to 15 kW
  • 130% positive peak modulation to 16.5 kW


Spurious and Harmonic

  • 80 dB or more below carrier at 15 kW
  • Meets ITU-R SM.328-10
  • Meets ITU-R SM.329-9


AC Input


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


Power Supply Variation

  • ±10% voltage, 47 Hz to 63 Hz*


Power Consumption

  • 9 kW typical at 15 kW, 0% modulation
  • 8 kW typical at 15 kW, 100% modulation


Cos (theta)

  • 95 typical




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



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


Cooling Air Requirements

  • 2,550 m3/hr (1,500 CFM)



  • Meets EN60215: 1996 Safety Requirements for Radio Transmitting Equipment





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



  • Main transmitter cabinet with modules installed: 567 kg (1250 lbs)
  • Power transformer: 262 kg (578 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), 1 kHz tone at 95% modulation (typical)


Intermodulation Distortion

  • SMPTE 1:1 Ratio, 60Hz/7kHz, 95% Mod Peak – 0.5% @ 25 kW (typical)
  • DIM-B, 2.96kHz/9kHz, 80% Mod Peak – 0.5% @ 25 kW


Carrier Shift

  • 5% or less


Hum and Noise

  • -65 dB or better below 25 kW, 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.





  • DC Voltages (B+, PA and 15V)
  • DC Current
  • Sample Levels (PDM and RF Drive)
  • Fan Speeds
  • Heat Sink Temperature



  • DC Voltage levels (15V, 5V, 30V, 48V and B+)
  • Rectifier Fan Speeds
  • DC Current
  • Rectifier Heat Sink Temperature
  • AC Voltage



  • 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



  • 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



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



  • 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
  • SNMPv1


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



Product Resources

Comments are closed.