FM Transmitter


  • High power and high efficiency due to modern design technology
  • Rugged, reliable and highly redundant design
  • Final amplifiers voltage supply proportional to RF output power
  • Dedicated built-in power supply for each amplifier module
  • Exciter digital based FM modulator
  • Fully broadband power amplifier modules 87.5 –108 MHz
  • Easy replacement of RF amplifier modules during operation for simplified maintenance
  • Internal GPS option for high frequency stability and synchronous FM application
  • Bidirectional interactive GSM monitoring and controlling system (option)
  • Built-in Radio Data System
  • Built-in high quality digital stereo coder
  • Modular central control system for straightforward monitoring and in-depth diagnostics
  • Web, SNMP remote control, and parallel commands remote control interface
  • Configurable in system N+1 controlled by Logic N+1 controller

Product Detail

High Power, High Efficiency
The Siel  air-cooled series offers high power and high efficiency due to design technology and power voltage regulation circuit. This regulation mechanism in amplifier modules yields a major increase in efficiency. The supply voltage for the power transistors is adjusted as a function of the output power and frequency significantly improving efficiency.

Maximized Coverage with the Exciter
Utilizing the digital exciter, the benefits that customers can realize are improved stereo signal-to-noise, AM noise null, and the ability to synchronize to an external reference for use in on-channel booster systems. The  exciter provides a flawless signal with complete technical and regulatory compliance for solid-state transmitters. Both analog AF signals and digital signals in line with bit-serial AES/EBU protocol can be processed. Left/Right,MPX, RDS or SCA signals can be used as modulation signals.

Monitoring, Web interface and remote control
Each power amplifier module has dedicated control and monitoring to support on/off functionality warnings and alarms for reflected power, temperature, power overdrive and other measures. The transmitter control unit handle both internal and external communications and provides all control functions. All transmitter, cooling system, exciters and amplifiers parameters required for diagnostics can be retrieved locally as well as remotely from anywhere in the world via a standard (IP) protocol and standard software (web browser,SNMP). This allows to accurately evaluate the transmitter status of unattended stations.

GSM system
Transmitters can be provided with internal GSM monitoring and controlling system as requested option. This feature allows the operator to monitor the transmitter status via GSM command receiving SMS from transmitter unit about status and eventually failure states. Using GSM system, the operator can also send remote control to the transmitter unit.

Enhanced Redundancy
The transmitter supports a range of backup options simplifying on-air servicing and eliminating costly interruptions. In dual-drive systems, the integrated control system monitors exciters and switches control of RF feed. Conventional standby systems such as exciter standby, (N+1) standby, passive standby can be implemented. High redundant design in amplifier modules also makes the Air-Cooled series a very rugged, reliable transmitters family.

Cooling system
The transmitters are air-cooled. Air cooling system includes internal blowers, which pull cool air from the front through a removable filter, and exhausts in the rear. An exhaust air extractor is also present on the top of the cabinet. Various air ducting configurations or external system taking air from cleaning room is available as option.

Primary Power 3-phase 50/60 Hz,
415/400/380/220V single-phase
50/60 Hz, 240/230/208/127/115V
AC Line Variation ± 15 %
Max Installation Altitude 2000 m above sea level
(>2000 m on request)
Operating Temperature Range -5 °C to +45 °C
Permissible Relative Humidity 95%, non-condensing
Cooling Method Forced Air

Output Parameters
FM Modulation Modes Stereo, Mono, MPX
Output Frequency Range 87.5 to 108 MHz
Tuning Resolution 1Hz
Output Impedance 50 Ω, unbalanced
Permissible VSWR < 1.5
Frequency Drift (per year) < 1×10-6
Frequency Drift (per year)
(with optional GPS Board)
< 1×10-7
Ext. Time and Ref. Frequency
Reference Frequency 10 MHz
Reference Impedance 50 Ω
Reference Connector BNC
Time Ref. Input Frequency 1 PPS
Analog L/R Input XLR, 600 to 3kΩ balanced
AES/EBU Audio Input BNC, 75 Ω
MPX Input XLR 600 to 3kΩ
External 10 MHz Clock Input BNC
External 1 PPS Clock Input BNC
Stereo Transmission Quality
Left/Right inputs, internal stereo coder function enabled
Deviation ± 75 kHz Nominal
Amplitude Frequency Response < 0.4 dB, 20 Hz to 15 kHz
THD < 0.01%
THD+N < 0.04%
Crosstalk (20Hz to 15 KHz) > 65 dB
S/N Weighted > 75 dB qpk
S/N Unweighted > 85 dB rms, 80 dB qpk
MPX Input, external stereo coder
Deviation ± 75 kHz Nominal
Amplitude Frequency Response < 0.05 dB, 40 Hz to 67 kHz
THD < 0.01%
THD+N < 0.04%
Crosstalk (20Hz to 15 KHz)
Crosstalk (40Hz to 15 KHz)
> 55 dB
> 45 dB
S/N Weighted > 75 dB qpk
S/N Unweighted > 85 dB rms, 80 dB qpk
Remote Control
Serial Remote RS232
Ethernet/SNMP RJ-45
GSM Modem (optional)