R&S®FK855U HF Antenna Tuning Unit

For matching HF transceivers to antennas used in submarine applications

  • Overview

Key Facts

  • Tuning range 1.5 MHz to 30 MHz
  • Fully automatic tuning
  • 400 W CW and PEP at 100 % duty cycle
  • 1000 W CW and PEP with restrictions

Brief Description

  • Silent tuning over the entire frequency range from 1.5 MHz to 30 MHz
  • Repeated tuning

Key Facts

    • Tuning range 1.5 MHz to 30 MHz
    • Fully automatic tuning
    • 400 W CW and PEP at 100 % duty cycle
    • 1000 W CW and PEP with restrictions
    • Tuning of all rod, whip and broadband antennas used in submarine applications
    • Low probability of intercept (LPI)
    • Extremely short setting time
    • Silent tuning over the entire fequency range from 1.5 MHz to 30 MHz
    • Maintenance-free
    • MTBF 12 000 h (calculated)
    • Continuous monitoring of operational status
    • Extremely rugged design

    The R&S®FK855U matches rod and whip antennas, as they are used in submarine applications, to the RF output of the Transceivers R&S®XK2500/ R&S®XK2900.

    It can handle power up to 400 W CW and PEP at a 100 % duty cycle and up to 1000 W with restrictions. The R&S®FK855U operates in the frequency range from 1.5 MHz to 30 MHz where it performs an antenna impedance transformation into 50 Ω in both the receive and transmit mode. Additionally, it provides preselection in the receive mode.

    Owing to the silent tuning features of the Transceivers R&S®XK2500 and R&S®XK2900, low probability of intercept (LPI) is enhanced.

  • Design

    The rugged design of the R&S®FK855U allows it to be operated continuously 24 hours a day especially on board of submarines, installed in a submarine communication mast

  • Bite

    The ATU is included in the continuous monitoring of the system so that deviations from the normal operating status are displayed on the control unit.

  • EMC and overvoltage protection

    All circuit boards are equipped with ECM filters. For protection against overvoltage as produced by lightning strokes to the antenna, the R&S® FK855U output is provided with lightning protection.

Brief Description

Silent tuning over the entire frequency range from 1.5 MHz to 30 MHz

Before the ATU can be used for an application, it must be connected to an antenna to "learn" its characteristic. Learning takes place in a user-defined frequency range in the HF band (1.5 MHz to 30 MHz).

The ATU "learns" the antenna characteristic by receiving tuning data for a maximum of 1500 predefi ned frequencies. Once the tuning data for these frequencies is known and stored, the typical ATU setting time to these channels is less than 5 ms.

Repeated tuning

A change in environmental conditions may slightly alter the actual antenna tuning data as compared to the stored data.

The quality of antenna matching is therefore checked during operation by means of an integrated VSWR measuring device. If the required VSWR (<1.5:1) is not attained, the ATU can be retuned in less than (typ.) 100 ms.

The advantage for the user is low probability of intercept (LPI), since ATU frequency setting is performed very quickly and without any emission of RF power.

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