Marker Beacons

Technology Overview

In aviation, marker beacons are generally used in conjunction with an instrument landing system (ILS) to give pilots an indication of the distance between the airplane and the runway threshold. Ground-based marker beacons consist of three VHF radio beacons vertically transmitted from highly directional antennas at three defined distances from the runway threshold. When an airplane flies over the markers (outer, middle, inner marker), the airplane’s marker beacon receiver provides the pilot with both a visual and an acoustic signal.

For the outer marker at a distance of 7200 m to the runway, a 400 Hz tone is amplitude modulated on a 75 MHz frequency carrier and indicated to the pilot by an interrupted 400 Hz tone and a flashing blue light. The middle marker at 1050 m is indicated by a 1300 Hz tone and a flashing amber light and the inner marker at 300 m by a 3000 Hz tone and a flashing white light. The flashing light and the morse-coded audio tone provide the pilot with an indication of the distance to the runway.

Applications

Marker beacons are used in conjunction with an ILS as a navigation aid in international civil and military air traffic. They provide aircraft pilots with data about the position relative to the runway threshold. Marker beacons are gradually being replaced by other established technologies such as GPS or DME, making marker beacons increasingly obsolete.

Rohde & Schwarz Test Solutions

Air navigation systems such as marker beacons are subject to the highest safety requirements. Rohde & Schwarz offers unique and highly reliable test solutions for terrestrial navigation systems including marker beacon transmitter and receiver testing – from R&D to production as well as during calibration, installation and maintenance.

Excellent accuracy and highest spectral purity make the R&S®SMA100A signal generator ideal for marker beacon receiver testing. The generator simulates marker beacon and COM/ID signals in line with ICAO standards.

The R&S®EVS300 ILS/VOR analyzer offers the high accuracy, fast measurement speed and low weight required in test applications for ground and flight inspection of VOR and ILS ground infrastructure in the field. The portable analyzer also features FFT, frequency scan and oscilloscope options in a single box for maximum flexibility in the field.

Key Parameters

Standardization

To ensure the accurate operation of radio navigation systems, the International Civil Aviation Organization (ICAO) has standardized the critical parameters for marker beacons in Annex 10, Volume 1. The conformance of marker beacon installations with these standards is regularly controlled, calibrated and certified by flight inspection organizations.