Presentation on theme: "LECTURE 3. Objectives Introduction to various types of antenna used in aviation Introduction to frequency used in aviation and their characteristics."— Presentation transcript:
Objectives Introduction to various types of antenna used in aviation Introduction to frequency used in aviation and their characteristics
Antenna An antenna is a device which provides means for radiating or receiving radio waves. In communication link, the transmitter is connected through a cable to one antenna, the signal is radiated to another antenna, and then passes through another cable to the receiver. Communication between aircraft and airfields must use free space propagation, as do radar and navigation systems. Broadcast systems such as TV or radio can used one transmitter to serve many receivers via a free space link.
Illustration Transmitting antenna Receiving antanna FREE SPACE Electromagnetic Wave propagates Tx line
Antenna as transition device Wire Antennas Printed Circuit Antenna
Types of antenna Array Antenna Reflector antenna Aperture antennas
Why choose a correct antenna? Other than receiving and transmitting energy, an antenna in an advanced wireless system is usually require to optimize the radiation energy in some directions. For wireless communication systems, the antenna is one of the most critical components. A good design of the antenna can relax system requirements and improve overall system performance e.g: A TV for which the overall broadcast reception can be improved by utilizing a high performance antenna.
Antenna on Aircraft Type and size of antenna varies with the different types of aircraft. The location of antenna depends on the design of aircraft.
Discussion on frequencies used for aviation
Frequency Band BandFrequency LF3 0– 300kHz MF300kHz– 3MHz HF3 – 30MHz VHF30 – 300MHz UHF300MHz– 3GHz SE
Frequency Band The use of the various Radio Frequencies all over the World is allocated by ITU (International Telecommunications Union. The Radio Frequencies are being used in various field, amongst them include : FM Radio Broadcast Television Broadcast Land Mobile Stations (Emergency, Business, and Military) Amateur Radio Marine Communications AIRCRAFT COMMUNICATIONS AIR TRAFFIC CONTROL AIR NAVIGATION SYSTEMS (e.g.VOR/DME,NDB)
VLF-Very Low Frequency Can be used for communication with submerged submarines and they have some use for this purpose aboard aircraft. VLF were very important to air navigation years ago, but became increasingly less important as more reliable systems operating at higher frequencies were developed and became widely available.
HF-High Frequency HF-High Frequency (3– 30 MHz) HF: This is the basic band for long-range communications, mainly because its transmissions are reflected from the ionosphere. HF1 = Typically used for Long-Range ATC communications HF2 = Back up to HF1. (frequently used to listen to the BBC to overcome boredom on longer flights)
HF-High Frequency HF undergoes the “Skywave” phenomena where ionosphere refracts the HF radio waves and can be utilized for medium and long range radio communications, HF transmissions are reflected from the ionosphere.
Disadvantage of HF Efficiency of HF is affected by: All kinds of electrical interference caused by ionosphere disturbances such as thunderstorms. This provides the typical radio noise. Other weather phenomena: Sunlight Season Solar Activity
VHF: Very High Frequency VHF-Very High Frequency (30 – 300MHz) Normally, VHF between 100 to 200MHz are used for ATC communications, emergency and navigational aids (VOR, DME, ILS). VHF1 = Used for ATC communications VHF2 = Emergency frequency monitoring. VHF3 = Typically used for Data transmissions (ACARS).
Characteristics of VHF Radios The propagation characteristics of VHF are optimized for short range communications. The range varies depending the atmospheric conditions but normally is about 180. nautical miles. However it is more prone to blockage by Land Features, buildings, and its lower spectrum frequencies.
Specific Usage VHF Voice communication Source Carrier 118-121.4 MHzAir Traffic Control 121.5 MHzEmergency 121.6 – 121.9 MHzAirport Ground control 123.1 MHzSearch And Rescue 123.675-128.8 MHzAir traffic control 128.825-132.0 MHzEn Route 132.05-135.975 MHzAir traffic control
The use of VHF for Aeronautical Communications in Malaysia In Malaysia the use of VHF Radio Systems for Aviation purposes are wholly owned by DCA Malaysia and are stationed on various Hill Stations owned by Telekom Malaysia
UHF: Ultra High Frequency UHF-Ultra High Frequency (300MHz– 3GHz) UHF: similar to VHF, but is restricted mainly for military aviation use. In Malaysia, UHF is mostly used by Combat Aircraft of the Royal Malaysian Air Force (RMAF). Other applications includes Navigations/Landing Aids such as the Glide path component of the ILS(Instrument Landing Systems).
UHF: Ultra High Frequency UHF broadcasting was used outside Kuala Lumpur and the Klang Valley by private TV station TV3 in the late 80’s with the Government stations only transmitting in VHF (Bands 1 and 3). At current count, there are 4 distinct UHF signals receivable by an analog TV set in the Klang Vall, Channel 25 (8TV), Channel 29 (TV3 UHF Transmission), Channel 37 (NTV7) and Channel 39 (TV9). Channel 35 is usually allocated for VCR,s, decoder units (i.e.the ASTRO and MiTV set top boxes) and other devices that have an RF signal generator (i.e. consoles).
Question Names two types of two way communication radios (frequencies) used on an aircraft? What are their purposes? List the benefit of the new communication system for passengers.(broadband for surfing the net,SMS,and phones.)
Benefit of the new communication system for passengers Some of the benefits of passengers are the broadband, SMS, Phones, these are good to keep business travelers well into their schedules, this allows them to work while they fly, and this alleviates the problems once they land, they can track their flights, know exactly when they will land, etc...
Onboard Communications Radio is the choice of communications medium for air to ground communications, but there are requirements for considerable onboard communications. such applications as voice communications among flight crew members between flight crew members and passengers. This communication is provided by a system called an interphone and usually works in conjunction with an audio panel, which not only provides the interphone function but switches speakers and headphones between the various communications and navigation systems aboard the aircraft.
Audio Panel A number of audio sources in the aircraft that the flight crew should monitor Different transceivers for communication Navigation equipment (for station identifier) ADF, VOR, DME, MLS Surveillance equipment – TCAS Method of selecting which navigation systems will be heard on headphones/speaker Use audio control panel