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Beacons – Navigation Antennas

Beacons – Navigation Antennas #

To find its way to its destination and communicate with air traffic control and/or other aircraft, an airplane uses a variety of radio frequencies. The onboard radio equipment uses a variety of antennas including Beacons, each one created for a specific frequency band, in order to do this. Each of these antennas has a unique frequency and application properties, as well as positioning on the aircraft. There are requirements for even the connection between the antenna and the avionics. Some people may be curious as to whether you can paint the airplane antennas. Consult the antenna’s manufacturer for more information as it depends on the type of paint, frequency, and bandwidth. Just don’t paint them if you are unsure. 

ADS-B, Transponders & DME #

A radio receiver and transmitter combined into one unit, the transponder of an aircraft receives ATC interrogation on 1030 MHz and broadcasts its coded reply on 1090 MHz. These can also be used by ADS-B and distance measuring equipment (DME), as they have a greater frequency range (bandwidth). The tiny increase in weight and requirement to mount it properly in line, which prevents it from serving as a small rudder, are drawbacks.

DME functions by transmitting a signal of interrogation to a ground station and receiving and processing the response. The frequencies used by the transponder (1030/1090 MHz) fall within the DME frequency band, which spans 962 MHz to 1213 MHz. The ADS-B system utilizes 978 MHz as well. This explains why ADS-B, DME, and transponders (A/C/S) can all use the same antenna (blade types rather than the monopole). To establish the frequency of the DME receiver, a DME frequency matched with a VOR must be chosen.

Antenna Location #

This antenna will either be mounted on the aircraft’s belly or back, far from other transmitting antennas and delicate receivers. TCAS systems typically employ two antennas for full coverage around the aircraft, which are often located at the top and bottom of the fuselage to prevent interference.

Emergencies, ELT Antenna #

The Emergency Locator Transmitter (ELT) has traditionally transmitted on the VHF band at 121.5 MHz (military aircraft utilize 243 MHz, which is a third harmonic of the base frequency). Due to restrictions, the usage of 121.5 MHz is being phased out for satellite service, and 406 MHz ELTs are now required in the majority of nations.

ELT Antenna Location #

For increased survival, the ELT ought to be mounted in the aircraft’s tail portion. The antenna, which is often a little whip-style device that comes with the ELT and is situated towards the tail, is the last to arrive at the scene of the collision but has the best chance of surviving it. You risk receiving very large fines if you tamper with this device and cause a false alarm. Make sure to follow the installation guidelines exactly. If you want to test this gadget, make sure to do it within the first five minutes of the hour, maintain a radio nearby tuned to 121.5 MHz (so you can check the low level homing signal), and send no more than three sweeps at a time.

Satellite Monitoring #

The COSPAS-SARSAT satellite system has ceased monitoring 121.5 MHz and 243 MHz as of January 1st, 2009. From this moment forward, satellites will only track 406 MHz. The Russian phrase “Cosmicheskaya Sistyems Poiska Avariynich Sydov,” or “Space System for the Search of Vessels in Distrass,” is referred to by the acronym COSPAS.
SARSAT, or Search And Rescue Satellite Aided Tracking, is an abbreviation.

After the Flight #

If the airplane has more than one radio, tuning the other to 121.5 MHz would be useful. In this manner, you can alert the closest ATC unit about any received alarms. Similarly, after a flight, tune to 121.5 MHz shortly before turning off the radios to check sure your ELT was not accidentally activated due to a relatively bumpy landing. This method is still effective because the majority of modern 406 MHz ELTs have a 121.5 MHz homing signal.

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