RAN Lecture 2: Radio Theory

Learning Outcomes At the end of this lecture, the student should be able to: Describe about radio principles Explain the applications of HF, VHF, UHF in aviations

What is RADIO? Radio is wireless transmission through space of ELECTROMAGNETIC WAVES in the approximate frequency range from 10kHz to 300’000MHz.

Why learn radio theory? Radio theory is essential knowledge for the understanding of the reasons why particular frequencies are used for particular navigational aids system (DME,VOR & etc)

What is Communication For example, Communication is a process of transmitting INFORMATION from one location to another MEDIUM is required for the delivery of the information to be exchanged. For example, Transmission medium for television or telephone is cable or fiber optics Communication was the first requirement for controlling aircraft traffic.

History of Communication Radio transmission starts in US in 1920 with the invention of RADIO TRANSMITTING EQUIPMENT that capable of transmitting voice and music.

Radio Transmitting Equipment TRANSMITTER : a device used to generate and transmit radio signals [ELECTROMAGNETIC WAVES]. RECEIVER : a device that receives incoming radio signals and converts them to sound or light. Example: receiver on radio or television converting broadcast signals into sound or images.

Radio Transmission In communication link, the TRANSMITTER is connected through a cable to one ANTENNA. ANTENNA is a device which provides means for radiating or receiving radio waves. The signal is radiated to ANOTHER ANTENNA, and then passes through another cable to the RECEIVER. Broadcast systems such as TV or radio can used one transmitter to serve many receivers via a free space link.

Types of antenna Reflector antenna Array Antenna Wire Antennas

Electromagnetic Wave

Direction of Propagation Electromagnetic Wave Electromagnetic Wave = Electric wave + Magnetic Wave Electromagnetic wave are used to transmit information by wave motion. Both waves oscillate at the same frequency z x y Electric Field Magnetic Field Direction of Propagation A wave is a disturbance that is produced repeatedly, & transfer energy. Often in the form of vibration & oscillation.

Electromagnetic Wave The types of electromagnetic wave including: RADIO WAVES (for TV, radio, aircraft communication) Microwaves (radar, microwave oven) Infrared radiation (Body screening, remotes) Visible Light (Bulb) Ultraviolet (Medical Equipments) X-rays (Medical X-rays, Baggage Screening) Gamma rays (Space Observations) When radio communication is passed from one location (where it originates) to another, it is sent in the form of waves. These waves reach receiving antennae and interact with the electric charges in the antennae wires. The radio waves have electric and magnetic fields that can interact with the wires.

Radio waves Everyday technologies that depend on radio waves: Standard broadcast radio and television Wireless networks Cell phones GPS receivers Aircraft Communications ATC communications Satellite communications Police radios, Wireless clocks, Cordless phones , Garage door openers When radio communication is passed from one location (where it originates) to another, it is sent in the form of waves. These waves reach receiving antennae and interact with the electric charges in the antennae wires. The radio waves have electric and magnetic fields that can interact with the wires. Bluetooth networking transmits data via low-power radio waves. It communicates on a frequency of 2.45 gigahertz (actually between 2.402 GHz and 2.480 GHz, to be exact).

Properties of Radio Waves Radio waves are radiated energy. Subject to attenuation & interference Consist of oscillating electric and magnetic fields Properties of Radio Waves Properties of Radio Waves A radio wave that leaves a transmitter has the following properties: They consist of oscillating electric and magnetic fields that are at right angles to each other and at right angles to the direction of propagation They require no supporting medium They can be reflected, refracted and diffracted They are subject to interference and Doppler effect They can pass through an opaque object such as a building although they do suffer attenuation in doing so Can be reflected, refracted and diffracted In free space, they travel in straight lines at the speed of light c = 3108 m/s.

The radio wave is an alternating waveform and as such the following terms are used: Period The duration of one cycle (T). In the figure above T = 1/100 seconds Velocity The speed with which a wave travels through a given medium. For a radio wave this is 300 000 000 metres per second better expressed as 300 X 106 m/s Frequency The number of complete waves passing a fixed point in one second, denoted by the symbol “f”. Usually expressed as Hertz (Hz). It is obvious that f = 1/T Wavelength The distance between similar points on successive waves or the distance occupied by one complete cycle when travelling in free space (AB), denoted by the symbol λ (Lambda) Amplitude The maximum height of the wave. This can be positive or negative. The positive amplitude is represented by “b”

Radio Wave f = c/l [c is speed of & l is wavelength] In free space, radio wave travel in straight lines at the speed of light c = 3108 m/s. Frequency is the number of wave cycles that occur within 1 second. It is measured in Hertz. f = c/l [c is speed of & l is wavelength] Wavelength is the distance a radio wave travels during one cycle. Amplitude is the strength of the signal. THE HIGHER THE FREQUENCY, THE SHORTER THE WAVELENGTH Frequency is the number of complete waves passing a given point per second.

Example f = c/l f= 3108 m/s / 2.5m f= 120’ 000 000 Hz f= 120 MHz What is the frequency of an Air Traffic Control operating at a wavelength of 2.5m? [speed of light c = 3108 m/s.] f = c/l f= 3108 m/s / 2.5m f= 120’ 000 000 Hz f= 120 MHz

Example f = c/l f= 3108 m/s / 0.3m f= 1 x 109Hz @ 1000 x 106 Hz What is the frequency of Distance Measuring Equipment (DME) operating at a wavelength of 0.3m? [speed of light c = 3108 m/s.] f = c/l f= 3108 m/s / 0.3m f= 1 x 109Hz @ 1000 x 106 Hz f= 1 GHz @ 1000 MHz

Example What is the wavelength of ILS Localizer operating at a frequency of 100MHz? [speed of light c = 3108 m/s.]

Example What is the wavelength of an aircraft communications operating at a frequency of 30MHz? [speed of light c = 3108 m/s.]

RADIO WAVE can be reflected. Reflection is the change in direction of travel of a wave, due to hitting a reflective surface. This is the same characteristic displayed by a radio wave as it is reflected from the ionosphere. When reflection of wave happen, the wavelength, frequency and speed do not change. Earth can cause radio wave to take path other than straight line Significant characteristics of earth Conductor of electricity Able to conduct low-frequency Conductor is a material or device that conducts heat or electricity. Another conductor is also the ionosphere layer. Ionosphere is the layer of ionized gasses. Ionosphere layer can act as reflector of radio waves.

RADIO WAVE can be refracted Refraction occurs when the radio waves go from one medium to another medium. Refract means change the direction of radio propagation of by causing them to travel at different speeds and at different direction along the wave front.

RADIO WAVE can be diffracted. Diffraction of waves is spreading out of waves when they move through a gap or around an obstacle. Frequency, wavelength and speed of waves do not change. The direction of propagation and the pattern of waves are change. Direction of wave propagation Diffraction is the spreading out of waves, for example when they travel through a small opening. Obstacle

Radio Wave subject to attenuation Radio wave can pass through an opaque object, but may suffer attenuation. Attenuation is the loss of wave energy as it travels through a medium . Or in short word the strength of the radio wave is reduced.

Radio wave subject to Interference Interference is the prevention of reception of a clear radio signal. Interference also means the superposition of two or more waves from same sources. There are a large number of users of radio communication How can these users coexist without interfering with each other? Frequency are everywhere

How to avoid interference Radio communicators can operate without interfering by choosing different radio frequency To eliminate confusion and facilitate international understanding the majority of the countries of the world have joined in establishing standard classification systems. The use of the various Radio Frequencies all over the World is allocated by ITU (International Telecommunications Union).

Exercise Why do you think airline attendants ask passengers to turn off electronic devices including phones, radios, TVs and computer during take-off and landing?

Radio Frequencies Classification System

Table of Radio Frequencies Extremely High Frequency Description Abbreviation Frequency Wavelength Very Low Frequency VLF 3 KHz - 30 KHz 100,000m - 10,000m Low Frequency LF 30 KHz - 300 KHz 10,000m - 1,000 Medium Frequency MF 300 KHz - 3 MHz 1,000m - 100m High Frequency HF 3 MHz - 30 MHz 100m - 10m Very High Frequency VHF 30 MHz - 300 MHz 10m - 1m Ultra High Frequency UHF 300 MHz - 3 GHz 1m - 0.10m Super High Frequency SHF 3 GHz - 30 GHz 0.10m - 0.01m Extremely High Frequency EHF 30 GHz - 300 GHz 0.01m - 0.001m

Band Frequency LF 30– 300kHz MF 300kHz– 3MHz HF 3 – 30MHz VHF UHF 300MHz– 3GHz These adjectival designations are convenient in referring to transmission in those bands allocated for radiocommunication by aircraft.

Surface Wave (Ground wave) Wave Propagation There are three principle paths which radio waves may follow over the earth between the transmitter and the receiver: Surface Wave (Ground wave) Wave Propagation Sky wave Radio propagation also can be said as the transmission of radio waves It is depends upon the frequency of the radiated signal. Radio energy is most efficiently propagated by only one of the three main methods: Space waves

Wave Propagation

Line of Sight: Clear path between transmitting and receiving antennas Follows the contour of the Earth Radio waves radiated from the transmitting antenna in a direction toward the ionosphere Long distance transmissions Sky wave strike the ionosphere, is refracted back to ground, strike the ground, reflected back toward the ionosphere, etc until it reaches the receiving antenna Skipping is he refraction and reflection of sky waves Line of Sight: Clear path between transmitting and receiving antennas

Wave Propagation Surface Wave (Ground Wave) A wave which follows the contours of the earth’s surface. Propagate Low Frequencies (LF,MF) Used for short distance radio transmissions Sky Wave A wave that is refracted by the Ionosphere and returned to earth. Propagate Middle Range Frequencies (HF,VHF). Used for long distance transmissions The Ionized layers within ionosphere have the ability to reflect high frequency radio waves . Space Wave: do not reflect off ionosphere but continue into space. It does not follow the curvature of the earth. This line-of-sight characteristics means reception dependant on altitude. Used for VHF Transmissions.

Wave Propagation Space Wave A wave which is line of sight (reception dependant on altitude). Propagate Upper Range Frequencies. Used for VHF/UHF Transmissions.

Application of HF, VHF & UHF

Antennas on Aircraft Type and size of antenna varies with the different types of aircraft. The location of antenna depends on the design of aircraft.

HF and VHF Usage on Aircraft 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). VHF1 = Used for ATC communications VHF2 = Emergency frequency monitoring. VHF3 = Typically used for Data transmissions

HF-High Frequency HF-High Frequency (3– 30 MHz) HF is the basic band for long-range communications, mainly because its transmissions are reflected from the ionosphere. HF is widely used for domestic aircraft voice communications.

HF transmissions are reflected from the ionosphere. HF-High Frequency HF undergoes the “Skywave” phenomena where ionosphere reflects the HF radio waves and can be utilized for medium and long range radio communications. How ionosphere affect the propagation of radio waves? This is a layer of ionized gases at the upper reaches of the atmosphere that can act as a reflector of radio waves. 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

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). 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. VHF: This is the standard air traffic control band using speech modulation. It is limited to LOS, ‘line of sight’ range, normally about 200km. The lower end, 108-118MHz, is restricted to VOR/ILS functions, the remainder is used for civil aviation. All VHF can be used interchangeably for any VHF purposes.

Airport Ground control Specific Usage VHF Voice communication Source Carrier 118-121.4 MHz Air Traffic Control 121.5 MHz Emergency 121.6 – 121.9 MHz Airport Ground control 123.1 MHz Search And Rescue 123.675-128.8 MHz Air traffic control 128.825-132.0 MHz En Route 132.05-135.975 MHz

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 At current count, there are also UHF signals receivable by Television, example, TV8, TV3, NTV7 and TV9 and ASTRO.