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Antenna remoting system, 50 Watt VHF for 4 Radios

FORAX-4VHF

FORAX-4VHF connects four FM radios operating in the 30-88 MHz frequency band to remote antennas 20+ km away using one single-mode optical fibre.  FORAX-4VHF offers a high performance alternative to conventional radio-to-antenna coaxial cables, affording great flexibility in antenna location plus opto-isolation for all the user’s radios. The optical fibre can have as much as 7 dB of optical loss, enabling uninterrupted fibre paths as long as 25 km.

A FORAX-4VHF antenna remoting system consists of a four-port Radio Interface Unit (RIU) and a four-port Antenna Interface Unit (AIU), both operating on 28 VDC vehicle/generator power. At the radio site, each RIU is connected by short coaxial cables to the Combat Net Radios’ antenna ports.  At the antenna site, each AIU is connected using coaxial cables to four VHF antennas. The AIU delivers 50 W RF power at each antenna port.

FORAX-4VHF functions as a long, loss-free link between the radios and the antennas. System limitations and installation difficulties associated with coaxial cable are overcome by the simplicity and performance of RF-over-Fibre connections.

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Radio Interface Unit (RIU) Antenna Interface Unit (AIU)
Operating Frequency
  • 30-88 MHz
  • Other frequency bands available upon request
  • 30-88 MHz
  • Other frequency bands available upon request
Transmit (TX) Power
  • 50 W adjustable to – 3 dB (25 W), – 6 dB (12 W), – 9 dB (6 W)
  • With optional serial interface, power level can be remotely commanded
  • 50 W adjustable to – 3 dB (25 W), – 6 dB (12 W), – 9 dB (6 W)
  • With optional serial interface, power level can be remotely commanded
Receive (RX) Sensitivity – 115 dBm (10 dB SINAD) – 115 dBm (10 dB SINAD)
RX/TX Switching Time
  • 1 ms with no frequency change; manual frequency changes implemented in < 10 ms
  • Supports hopping waveforms
  • 1 ms with no frequency change; manual frequency changes implemented in < 10 ms
  • Supports hopping waveforms
Co-site Performance
  • System auto-tunes filters to radio’s frequency upon first transmission
  • With optional serial interface, filter tuning can be remotely commanded
  • ≥ 10% carrier separation from nearby transmitters to achieve full RX sensitivity
  • 40 dB antenna-to-antenna isolation achieves full RX sensitivity (20 dB with high-perf. option)
  • System auto-tunes filters to radio’s frequency upon first transmission
  • With optional serial interface, filter tuning can be remotely commanded
  • ≥ 10% carrier separation from nearby transmitters to achieve full RX sensitivity
  • 40 dB antenna-to-antenna isolation achieves full RX sensitivity (20 dB with high-perf. option)
Radio TX Power into RIU, each port
  • 3-5 W nominal, 50 W survive
  • Excess TX power causes audible alarm
AIU TX Power into Antenna, each port 50 W adjustable to – 3 dB (~ 25 W), – 6 dB (~ 12 W), – 9 dB (~ 6 W)
Optical Loss in User’s Optical Plant < 7 dB optical
NOTE: To calculate optical loss, allow 1⁄4 dB per km plus 1⁄4 dB per SC/APC connector		 < 7 dB optical
NOTE: To calculate optical loss, allow 1⁄4 dB per km plus 1⁄4 dB per SC/APC connector
Optical Reflectance in User’s Optical Plant < – 50 dB optical < – 50 dB optical
System Packaging 2U tall chassis for 19-inch rack 3U tall chassis for 10-in rack
Power 18-32 VDC from tactical generator, 70 W 18-32 VDC from tactical generator, 1100 W maximum
Operating Temperature – 10°C to + 60°C – 10°C to + 60°C
Storage Temperature – 40°C to + 80°C – 40°C to + 80°C
Installation Notes
  • User supplies DC power, single-mode optical fibre from RIU to AIU.
  • Patch Cable Kits are optionally available with four coax cables for radios and two FO patch cables for the RIU and AIU.
  • User supplies DC power, single-mode optical fibre from RIU to AIU.
  • Patch Cable Kits are optionally available with four coax cables for radios and two FO patch cables for the RIU and AIU.
Available Options
  • SINCGARS Hopping Interface (FORAX-4VHF-SNAP)
  • Serial Interface (FORAX-4VHF-SIF)
  • High Performance RF Filters (FORAX-4VHF-HPF)
  • Field Kit (FORAX-4VHF-FK)
  • Patch Cable Kit (FORAX-4VHF-PCK)
  • Customer-Witnessed Factory Acceptance
  • Test (FORAX-FAT)
  • Extended Warranty (FORAX-4VHF-EW)
FORAX-4VHF - Antenna remoting system, 50 Watt VHF for 4 Radios