FK4115M HF Antenna Tuning Unit by Rohde & Schwarz

Companies & Organizations:


Rohde & Schwarz GmbH & Co KG
Muehldorfstrasse 15
81671 Muenchen

Tuning functionality

The R&S®FK4115M offers a 'silent tuning feature' over the entire frequency range from 1.5 MHz to 30 MHz.


Before this feature can be used, the ATU must be connected to the antenna to "learn" its characteristic. Learning takes place in an user-defined frequency range in the HF band (1.5 MHz to 30 MHz). The ATU "learns" the antenna characteristic by obtaining tuning data at certain fixed frequencies in the HF frequency band. Once the tuning data for these frequencies is known and stored, the typical silent setting time of the ATU is less than 5 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.


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 (nonsilent mode) in less than typ. 100 ms.



The ATU is included in the continuous monitoring of the entire 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 EMC filters. For protection against overvoltage as produced by lightning strokes to the antenna, the R&S®FK4115M output is provided with lightning protection.


Key Facts


The R&S®FK4115M matches rod and whip and wire antennas – as used in naval and stationary applications – to the RF output of the 150 W transceiver of R&S®M3SR Series 4100.


It can handle up to 150 W PEP or 100 W CW at a 100% duty cycle. The R&S®FK4115M 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 modes. Additionally, it provides preselection in the receive mode. The R&S®FK4115M has an extremely fast setting time for silent channels and allows frequency hopping operation in line with SECOM-H.


Particular attention has been paid to achieving effective lightning protection. The ATU is fully arc-protected against direct lightning strokes. It is tested to withstand arcs of 10 kV/10 kA.


Main features

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

Tuning of rod, whip and wire antennas

150 W PEP, 100 W CW at 100% duty cycle

Low probability of intercept (LPI)

Maintenance-free, rugged design

Frequency hopping capability (SECOM-H)

Defense Products & Services: FK4115M HF Antenna Tuning Unit by Rohde & Schwarz
Companies & Organizations: 
Country: Germany
Description: FK4115M HF Antenna Tuning Unit
Source of Information: Rohde & Schwarz GmbH & Co KG