ATA 23 Communication PDF - Lufthansa Technical Training

This document satisfies the requirements of the “DGCA KCASR 1 Part 66 Appendix I” and is approved for use at AU Fundamentals M13 AIRCRAFT AERODYNAMICS, STRUCTURES and SYSTEMS M13.4 Communication ATA 23 Rev.−ID:...

This document satisfies the requirements of the “DGCA KCASR 1 Part 66 Appendix I” and is approved for use at AU Fundamentals M13 AIRCRAFT AERODYNAMICS, STRUCTURES and SYSTEMS M13.4 Communication ATA 23 Rev.−ID: 1MAR2021 Author: WaH In compliance with: EASA Part-66; UAE GCAA CAR 66; CAAS SAR−66 FOR TRAINING PURPOSES ONLY Category B2 ©LTT Release: May. 05, 2021 M13.04 23 B2 E Training Manual For training purposes and internal use only. © Copyright by Lufthansa Technical Training GmbH (LTT). LTT is the owner of all rights to training documents and training software. Any use outside the training measures, especially reproduction and/or copying of training documents and software − also extracts there of − in any format at all (photocopying, using electronic systems or with the aid of other methods) is prohibited. Passing on training material and training software to third parties for the purpose of reproduction and/or copying is prohibited without the express written consent of LTT. Copyright endorsements, trademarks or brands may not be removed. A tape or video recording of training courses or similar services is only permissible with the written consent of LTT. In other respects, legal requirements, especially under copyright and criminal law, apply. Lufthansa Technical Training Dept HAM US Lufthansa Base Hamburg Weg beim Jäger 193 22335 Hamburg Germany E-Mail: [email protected] Internet: www.LTT.aero Revision Identification: The revision-tag given in the column ”Rev-ID” on the face Dates and author’s ID, which may be given at the The LTT production process ensures that the Training of this cover is binding for the complete Training Manual. base of the individual pages, are for information about Manual contains a complete set of all necessary pages in the latest revision of the content on that page(s) only. the latest finalized revision.  Air Traffic Control (ATC) –› VHF Cordless Telephone, HF Cordless Te lephone This is a communication rendered by the air traffic control institutions t o the aircraft to secure the safety and mobility of the air traffic. Aeronautical Operational Control (AOC) –› VHF Cordless Telephone, VHF Open Space Datalink, etc. This is communication by the aircraft pilot for normal navigation Communication and s o forth. Aeronautical Administrative Communications (AAC) –› VHF Open Sp ace Datalink and so forth This is business-use communication for airline companies, etc. Radio Navigation –› VOR, DME, TACAN, NDB This is communication for receiving response radio waves and catchin g information such as directions or distance by receiving 1st Day Navigation ground radio waves or emitting request radio waves from onboard. Aircraft Communication Satellite Navigation –› GPS This is communication to receive radio wave from multiple CNS artificial satellites and catch 3D position. Ground Surveillance –› ASR, SSR, ARSR, ORSR This is communication to determine the position of the aircraft by the g round radar. Automatic Dependent Surveillance –› Communicate the position data b y GPS, etc. by Inmarsat, MTSAT, etc. This is communication to attain navigation data automatically Surveillance without any human intervention, based upon the navigation data from the aircra ft. Cooperative Information Systems –› Development in progress. This is communication to attain 3D position data automatically without any human intervention by using multiple positioning satellites. Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Communication (ATA 23) M13.4 M13 AIRCRAFT AERODYNAMICS, STRUCTURES AND SYSTEMS M13.4 AVIONIC SYSTEMS (COMMUNICATION, ATA 23) FOR TRAINING PURPOSES ONLY! FRA US/O-5 WeR Jun 10, 2013 ATA DOC Page 1 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Basic Components M13.4 RADIO TECHNOLOGY Radio equipment can be divided into two broad categories: Transmitting equipment Receiving equipment. Both transmitting and receiving equipment consist basically of Electronic power supplies Amplifiers Oscillators. A basic radio communication system may consist of only a transmitter and a receiver, which are connected by the medium through which the electromagnetic waves travel (wire, wave guide, coaxial cable, nonconducting fluids or gases, air or vacuum. No medium is necessary for the propagation of electromagnetic waves). The transmitter comprises an oscillator (which generates a basic radio frequency), RF amplifiers, and the stage required to place the audio intelligence on the RF signal (modulator). The electromagnetic variations are propagated through the medium (space) from the transmitting antenna to the receiving antenna. The receiving antenna converts that portion of the transmitted FOR TRAINING PURPOSES ONLY! electromagnetic energy received by the antenna into a flow of alternating radio frequency currents. The receiver converts these current variations into the intelligence that is contained in the transmission. Sonic waves are converted to electrical signals by microphones. Loudspeakers convert electrical signals to sonic waves. HAM US/O53 KrA Apr 25, 2017 01|Radio SYS|L2|B2 Page 2 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Basic Components M13.4 Antennas Loudspeaker Microphone Transmitter Receiver FOR TRAINING PURPOSES ONLY! Figure 1 Basic Radio Communication System HAM US/O53 KrA Apr 25, 2017 01|Radio SYS|L2|B2 Page 3 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 AC Properties General Alternating current is the type of current that is used in the mains supply in the field of power engineering. In communications engineering both AC as well as DC is used. The abbreviation for alternating current is AC. Sinus Shape of Alternating Current Every generator containing rotating parts will create a sinusodial AC. So the sinusodial waveform is the standard for AC. Characteristics of AC is that the current I varies in direction (polarity) and in quantity in the circuit over a period of time t. In the positive half−wave the voltage goes from the 0 reference line up to the positive peak (+up) and from + up down to 0. Then the voltage goes in the opposite direction and rises from 0 to a negative peak value (−up) and falls from −up to the 0 reference line, as shown in the negative half−wave. The polarity and current magnitude change then repeats periodically. The same applies to the voltage. Cycle Time The positive and the negative half-wave together constitute one AC cycle. The time for one cycle to complete is called cycle time T. FOR TRAINING PURPOSES ONLY! As shown below the AC sine waveform repeats according to the cycle time T. The symbol for period is T. The period is measured in seconds (s). HAM OS/O-53 KrA Mar 07, 2017 01|AC Shape|L1|AB12 Page 4 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 U Positive Alteration 0 t T T 1 Period 1 Cycle Negative Alteration FOR TRAINING PURPOSES ONLY! AC Voltage Figure 2 AC Shape HAM OS/O-53 KrA Mar 07, 2017 01|AC Shape|L1|AB12 Page 5 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Frequency The frequency of AC is the number of complete cycles, i.e. oscillations, in one second. Frequency is also defined as the reciprocal of the cycle time T. frequency (f) = 1 cyc1etime (T) [f] = 1s = s− 1 = 1cps=Hz 1cps=Hz The higher the frequency the shorter the cycle time. The lower the frequency the longer the cycle time. The frequency states the number of cycles completed in one second. The symbol for frequency is f The frequency is measured in hertz (Hz). Very often frequency is expressed in kHz, MHz or GHz. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 07, 2017 02|FREQ|L1|AB12 Page 6 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 1s 1s FOR TRAINING PURPOSES ONLY! Figure 3 Frequencies HAM US/O-53 KrA Mar 07, 2017 02|FREQ|L1|AB12 Page 7 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Angular Frequency ω and Angular Velocity A sinus typically is created by a rotational movement, such as the rotation of a conducting wire loop in a magnetic field or the rotation of a magnet inside a generator. The rotational speed of the tip of the conductor or the magnet depends on the RPM and the diameter of the generator. With a length of 1, the rotational speed only depends on the RPM, it can be calculated by using the RPM (frequency f) and the circumference of the circle of the rotation. ω = 2π × f A sinusodial voltage is represented by a phasor or vector, where its length is given by the amplitude of the voltage while the RPM is determined by the frequency. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 07, 2017 03|Angular FREQ|L2|B2 Page 8 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Angular Frequency ω and Angular Velocity Angular velocity is a vector quantity, while on the other hand, angular frequency is a scalar quantity. The formula for both angular velocity and angular frequency is the same. Also, both are represented by ω. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 07, 2017 03|Angular FREQ|L2|B2 Page 8 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 S N AC-Generator FOR TRAINING PURPOSES ONLY! Line Chart Figure 4 Angular Frequency HAM US/O-53 KrA Mar 07, 2017 03|Angular FREQ|L2|B2 Page 9 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 FOR TRAINING PURPOSES ONLY! Figure 4 Angular Frequency HAM US/O-53 KrA Mar 07, 2017 03|Angular FREQ|L2|B2 Page 9 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Harmonic Waves Principle of Superposition of Harmonic Waves Non−sinusoidal oscillations can be resolved to sinus−shape by mathematics or graphic means. The sinusoidal wave with the same frequency as the non−sinusoidal wave is called basic oscillation or 1st harmonic. Multiples of the basic frequency are further harmonic waves. Rectangular waves can be resolved to a infinite number of uneven harmonics. Harmonic numbers and amplitudes are determined by the shape of the non sinusoidal oscillation. By superimposing the 1st, 3rd and 5th harmonic, an almost rectangular waveform with corresponding amplitude is obtained. The amplitude of a harmonic can be calculated by dividing the amplitude of the 1st harmonic by the number FOR TRAINING PURPOSES ONLY! of the actual harmonic. HAM US/O-53 KrA Mar 07, 2017 04|Harmonic Wave|L3|B2 Page 10 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Harmonic Waves Principle of Superposition of Harmonic Waves Non−sinusoidal oscillations can be resolved to sinus−shape by mathematics or graphic means. The sinusoidal wave with the same frequency as the non−sinusoidal wave is called basic oscillation or 1st harmonic. Multiples of the basic frequency are further harmonic waves. Rectangular waves can be resolved to a infinite number of uneven harmonics. Harmonic numbers and amplitudes are determined by the shape of the non sinusoidal oscillation. By superimposing the 1st, 3rd and 5th harmonic, an almost rectangular waveform with corresponding amplitude is obtained. The amplitude of a harmonic can be calculated by dividing the amplitude of the 1st harmonic by the number of the actual harmonic. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 07, 2017 04|Harmonic Wave|L3|B2 Page 10 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 U U 1st 1st 3rd 5th 7th 1st Harmonic f 1st, 3rd, 5th & 7th Harmonic f U U 1st 3rd 1st 3rd 5th 7th 9th 1st & 3rd Harmonic f 1st, 3rd, 5th, 7th, 9th Harmonic f U FOR TRAINING PURPOSES ONLY! 1st 3rd 5th 1st, 3rd & 5th Harmonic f All odd Harmonics Figure 5 Composition of Rectangular Waves HAM US/O-53 KrA Mar 07, 2017 04|Harmonic Wave|L3|B2 Page 11 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Illustration of the first three odd harmonics of the square-wave (with F the fundamental frequency). The blue line (lower panel) indicates a square-wave that results from summating the first three odd higher harmonics. The red line indicates a square- wave that would result from summating an infinite number of odd harmonics. FOR TRAINING PURPOSES ONLY! 1st, 3rd & 5th Harmonic All odd Harmonics Figure 5 Composition of Rectangular Waves HAM US/O-53 KrA Mar 07, 2017 04|Harmonic Wave|L3|B2 Page 11 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Triangular Waves Besides the rectangular type triangular and sawtooth waves are also possible. For triangular waves the odd harmonics have to be used, just like we did with the rectangular ones. But here the amplitude decreases with the square of the number of the harmonic. For sawtooth waves all harmonics are required, the odd ones and the even ones. Here their amplitude decreases with the number of the harmonic. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 07, 2017 04|Harmonic Wave|L3|B2 Page 12 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 U 1st 3rd 5th 7th 9th f U FOR TRAINING PURPOSES ONLY! 1st 3rd 5th 7th 9th f Figure 6 Triangular and Sawtooth Waves HAM US/O-53 KrA Mar 07, 2017 04|Harmonic Wave|L3|B2 Page 13 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Frequency Bands In communication engineering, there various frequency bands. The three most important frequency bands are: HF high frequency VHF very high frequency UHF ultra-high frequency. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 07, 2017 05|FREQ Bands|L2|B2 Page 14 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Mobile Comms Data Communication Communication Audio Frequencies Radio Broadcast Beam Radio Heat, Light, Telephone LW MW SW FM Radar X-Ray TV Broadcast Application Carrier-current Line Systems Satellite Broadcast Net- High Frequency El. Medicine Engineering works Tools Drying Power Inductive Heating, Annealing, Hardening, Melting Capacitive Heating Range, Designation EHF SHF UHF VHF HF MF LF VLF 100 101 107 109 1010 1011 FOR TRAINING PURPOSES ONLY! 102 103 104 105 106 108 Figure 7 Frequency Bands HAM US/O-53 KrA Mar 07, 2017 05|FREQ Bands|L2|B2 Page 15 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Wave Length  If a sinusodial voltage is applied to a conduction wire or an antenna, the voltage would propagate like a sinus-shaped wave. The propagation speed depends on the medium used, in free space (vaccum) it would propagate with the speed of light c. The length of such a wave can be calculated with the propagation speed v times the cycle time T or propagation speed divided by the frequency f. = c x T = c [m] f In a vacuum the speed of light c would be 299792 km per second or approximately 300000 km per second. The 300000 km per second is also used for propagation in air. The higher the density of the medium the lower the propagation speed will be. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 07, 2017 06|Wave Length|L2|B2 Page 16 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Wave Length  If a sinusodial voltage is applied to a conduction wire or an antenna, the voltage would propalgate like a sinus-shaped wave. The propagation speed depends on the medium used, in free space (vaccum) it would propagate with the speed of light c. The length of such a wave can be calculated with the propalgation speed v times the cycle time T or propagation speed divided by the frequency f. = c x T = c [m] f In a vacuum the speed of light c would be 299792 km per second or approximately 300000 km per second. The 300000 km per second is also used for propagation in air. The higher the density of the medium the lower the propagation speed will be. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 07, 2017 06|Wave Length|L2|B2 Page 16 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M11A|M13 AVIONIC SYSTEMS (ATA 23) Communication (ATA 23) M11.5.2|M13.4 FOR TRAINING PURPOSESONLY! Figure 6 Wavelength SaR 01.06.2007 HAM US/F-4 06|Wavelength|L1|AB1 Page 13 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Mobile Comms Data Communication Communication Audio Frequencies Radio Broadcast Beam Radio Heat, Light, Telephone LW MW SW FM Radar X-Ray TV Broadcast Application Carrier-current Line Systems Satellite Broadcast Net- High Frequency El. Medicine Engineering works Tools Drying Power Inductive Heating, Annealing, Hardening, Melting Capacitive Heating Range, Designation EHF SHF UHF VHF HF MF LF VLF FOR TRAINING PURPOSES ONLY! 100 101 102 103 104 105 106 107 108 109 1010 1011 Wave Lenght  3mm 30cm 30,000km 3,000km 3cm 30m 3m 3km 300km 30km 300m 300,000km Figure 8 Frequencies and Wave Length HAM US/O-53 KrA Mar 07, 2017 06|Wave Length|L2|B2 Page 17 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Aviation Frequencies General Radio frequencies up to 300 GHz are divided into decadic ranges. Each decade is designated as a frequency band. Radar frequencies are divided into special radar bands. Designations and Abbreviations of Radio Frequencies: RF Radio Frequency (carrier wave) IF Intermediate Frequency AF Audio Frequency. Radar Bands The frequencies which are used for radar technology are divided into special radar bands: Frequency Band for Radar Frequency Range Wave Length Range and Satellite Radio Mhz cm L 390 - 1550 77 - 20 S 1550 - 5200 20 - 5,8 C 3900 - 6200 11,8 - 7,3 X 5200 - 10900 5,8 - 2,5 FOR TRAINING PURPOSES ONLY! K 10900 - 36000 2,5 - 0,8 HAM US/O-53 KrA Mar 08, 2017 07|Radio FREQ|L1|AB12 Page 18 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Optical Emission f λ Communication Sy stems Navigation Systems Infrared 300 GHz 1 mm Radar EHF Weather Radar 9,375 GHz GHZ Bands Extremely High Frequency 30 GHz 1 cm 36 Doppler Radar 8,8 GHz K SHF 6,2 10,9 LRRA 4,25 − 4,35 GHz X Super High Frequency C 5,2 GPS L1: 1,5 GHz; L2: 1,2 GHz 3 GHz 1 dm S 3,9 ATC 1030 - 1090 MHz 1,55 UHF SatCom 1,5 Ghz DME 962 - 1213 MHz L ALTM 440 MHz Ultra High Frequency UHF Com 225−400 MH z 300 MHz 1m 0,39 GS 329,3 - 399,95 MHz VHF VOR 112 - 118 MHz VHF Com 118−137 MH z Very High Frequency LOC 108 - 112 MHz 30 MHz 10 m Marker 75 MHz HF High Frequency HF Com 2−30 MHz 3 MHz 100 m MF ADF 200 - 1750 kHz Medium Frequency 300 kHz 1 km LF FOR TRAINING PURPOSES ONLY! Low Frequency 30 kHz 10 km VLF Navigation 10 - 24 kHz VLF Very Low Frequency 3 kHz Identification Signals: 100 km DME: 1350 Hz Voice 300 Hz−3 kHz VOR, ILS, ADF: 1020 Hz 300 Hz Marker: 400, 1300; 3000 Hz 1000 km Figure 9 Aviation Radio Frequencies HAM US/O-53 KrA Mar 08, 2017 07|Radio FREQ|L1|AB12 Page 19 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 FOR TRAINING PURPOSES ONLY! Figure 9 Aviation Radio Frequencies HAM US/O-53 KrA Mar 08, 2017 07|Radio FREQ|L1|AB12 Page 19 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Radio Wave Propagation (How the radio signals travel) General Radio waves propagated into space are considered to be a radiant form of energy, similar to light and heat. They travel at approximately the speed of light. Conventional concepts of how the waves are radiated impose a severe strain on the average person’s imagination. The theory of wave propagation as presented in this text, although greatly simplified, has found general acceptance. Our major concern is in showing how to make antennas operate efficiently, both for transmission and reception, under various conditions. Various Components of a Propagated Electromagnetic Wave When a radio wave leaves a vertical antenna the field pattern of the wave resembles a huge doughnut lying on the ground with the antenna in the hole at the center. ▪ Part of the wave moves outward in contact with the ground to form the GROUND WAVE, and ▪ The rest of the wave moves upward and outward to form the SKY WAVE. The ground and sky portions of the radio wave are responsible for the two different methods of carrying the messages from transmitter to receiver. The ground wave is used both for short−range communications at high frequencies with low power and for long−range communication at low frequencies and with very high power. FOR TRAINING PURPOSES ONLY! Daytime reception from most commercial stations is carried by the ground wave. The sky wave is used for long−range high frequency daylight communication. At night, the sky wave provides a means for long−range contacts at somewhat lower frequencies. HAM US/O-53 KrA Mar 08, 2017 08|Wave PROP|L1|AB12 Page 20 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Sky Wave Antenna Ground Wave FOR TRAINING PURPOSES ONLY! Figure 10 Radio Wave Types HAM US/O-53 KrA Mar 08, 2017 08|Wave PROP|L1|AB12 Page 21 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Wave propagation defines the way in which waves are transmitted from an end to another. Basically, electromagnetic waves are allowed to be propagated from transmitting antenna to receiving through a channel of free space. So, the transmission of radio waves in space from an end to another can be done using any one of the three ways: ▪ Skywaves: HF Reflects from Ionosphere. ▪ Space waves: VHF and higher travels in a Line of Sight LOS. ▪ Ground waves: MF and lower follow the curvature of the earth High frequencies (From HF and above) only travel in a direct line. FOR TRAINING PURPOSES ONLY! Figure 10 Radio Wave Types HAM US/O-53 KrA Mar 08, 2017 08|Wave PROP|L1|AB12 Page 21 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 FOR TRAINING PURPOSES ONLY! Figure 10 Radio Wave Types HAM US/O-53 KrA Mar 08, 2017 08|Wave PROP|L1|AB12 Page 21 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 The Ground Wave The ground wave is responsible for most of the daytime broadcast reception. As it passes over and through the ground, this wave induces a voltage in the earth, setting up eddy currents. The energy used to establish these currents is absorbed from the ground wave, thereby weakening it as it moves away from the transmitting antenna. Increasing the frequency rapidly increases the attenuation so that ground wave transmission is limited to relatively low frequencies. Shore−base transmitters are able to transmit long−range ground wave transmissions by using frequencies between 18 and 300 kHz with extremely high power. Since the electrical properties of the earth along which the surface wave travels are relatively constant, the signal strength from a given station at a given point is nearly constant. This holds essentially true in all localities except those having distinct rainy and dry seasons. There the difference in the amount of moisture causes the conductivity of the soil to change. The conductivity of salt water is 5,000 times as great as that of dry soil. High power, low frequency transmitters are placed as close to the edge of the ocean as practical because of the superiority of surface wave conduction by salt water. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 08, 2017 09|Wave Types|L2|B2 Page 22 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 The operating frequency range in the case of ground wave propagation usually lies in the range from kHz to a few MHz (generally up to 2 MHz). Antenna Ground Wave The waves when emitted from the transmitting antenna, oscillates parallel to the surface of the earth. During transmission, when wave oscillates on the surface of FOR TRAINING PURPOSES ONLY! earth then oscillations induce a wave of equal magnitude but opposite polarity on the surface. Figure 11 Ground Wave HAM US/O-53 KrA Mar 08, 2017 09|Wave Types|L2|B2 Page 23 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 The Sky Wave That portion of the radio wave which moves upward and outward is not in contact with the ground and is called the SKY WAVE. It behaves similarly to the ground wave. Some of the energy of the sky wave is refracted (bent) by the ionosphere so that it comes back toward the earth. Some energy is lost in dissipation to particles of the atmospheric layers. A receiver located in the vicinity of the returning sky wave will receive strong signals even though several hundred miles beyond the range of the ground wave. FOR TRAINING PURPOSES ONLY! HAM US/O-53 KrA Mar 08, 2017 09|Wave Types|L2|B2 Page 24 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 The permissible frequency range in the case of sky wave propagation lies between 3 MHz to 30 MHz. Sky Ionosphe Antenn Wave re a Advantages of sky wave propagation 1.It supports large distance propagation. 2.The frequency range of operation is considerably high. FOR TRAINING PURPOSES ONLY! 3.Attenuation due to atmospheric conditions is less. Disadvantages of sky wave propagation 1.Long-distance propagation requires large-sized antennas. 2.Due to the presence of the ionosphere near and far during night and day respectively there exist variation in signal transmission in day and night. Applications Sky wave propagation is widely used in mobile and satellite communications as it needs suitable atmospheric conditions. Figure 12 Sky Wave HAM US/O-53 KrA Mar 08, 2017 09|Wave Types|L2|B2 Page 25 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Ionosphere The ionosphere is found in the rarefied atmosphere approximately 40 to 50 miles above the earth. It differs from other atmospheric parts in that it contains a much higher number of positive and negative ions. The negative ions are believed to be atoms whose energy levels have been raised to a high level by solar bombardment of ultra−violet and particle radiations. The rotation of the earth on its axis, the annual course of the earth around the sun, and the development of sun spots all affect the number of ions present in the ionosphere, and these in turn affect the quality and distance of electronic transmissions. The ionosphere is constantly changing. Some of the ions are returning to their normal energy level, while other atoms are being raised to a higher energy level. The rate of variation between high and low level of energy depends upon the amount of air present, and the strength of radiation from the sun, as well as the propagation relation to the earth’s magnetic field. At altitudes above 350 miles, the particles of air are far too sparse to permit large−scale energy transfer. Below about 40 miles altitude, only a few ions are present because the rate of return to a normal energy level is high. Ultraviolet radiations from the sun are absorbed in passage through the upper layers of the ionosphere so that below an elevation of 40 miles, too few ions exist to affect, materially, sky wave communication. FOR TRAINING PURPOSES ONLY! Densities of ionization at different heights make the ionosphere appear to have layers. Actually, there is thought to be no sharp dividing line between layers, but for the purpose of discussion, such a demarcation is indicated. HAM US/O-53 KrA Mar 08, 2017 09|Wave Types|L2|B2 Page 26 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 D-Layer The ionized atmosphere at an altitude of between 40 and 50 miles is called the ”D” layer. Its ionization is low and it has little effect on the propagation of radio waves except for the absorption of energy from the electronic waves as they pass through it. The ”D” layer is present only during the day. Its presence greatly reduces the field intensity of transmissions that must pass through daylight zones. E-Layer The band of atmosphere at altitudes between 50 and 90 miles contains the so called ”E”, layer. It is a well defined band with greatest density at an altitude of about 70 miles. This layer is strongest during daylight hours, and is also present, but much weaker, at night. The maximum density of the ”E” layer appears at about noon local time. The ionization of the ”E” layer at the middle of the day is sometimes sufficiently intense to refract frequencies up to 20 MHz back to the earth. This action is of great importance to daylight transmissions for distances up to 1,500 miles. F-Layer The ”F” layer extends approximately from the 90 mile level to the upper limits of the ionosphere. At night only one ”F” layer is present, but during the day, especially when the sun is high, this layer often separates into two parts, F1, and F2, as shown in the illustration. As a rule, the F2 layer is at its greatest density during early afternoon hours, but there are many notable exceptions of maximum F2 density existing several hours later. Shortly after sunset, the F1 and F2 layers recombine into a single F layer. FOR TRAINING PURPOSES ONLY! In addition to the layers of ionized atmosphere that appear regularly, erratic patches of ionized atmosphere occur at ”E” layer heights in the manner that clouds appear in the sky. These patches are referred to as Sporadic−E ionisation. They are often present in sufficient number and intensity to enable good VHF transmissions over distances not normally possible. Sometimes sporadic ionisations appear in considerable strength at varying altitudes and actually prove harmful to electronic transmissions. HAM US/O-53 KrA Mar 08, 2017 09|Wave Types|L2|B2 Page 26 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 FOR TRAINING PURPOSES ONLY! F E F2 F1 E D Night Day Figure 13 Ionosphere Layers HAM US/O-53 KrA Mar 08, 2017 09|Wave Types|L2|B2 Page 27 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 FOR TRAINING PURPOSES ONLY! Figure 13 Ionosphere Layers HAM US/O-53 KrA Mar 08, 2017 09|Wave Types|L2|B2 Page 27 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Ionosperic Effects Effect of Ionosphere on the Sky Wave The ionosphere has many characteristics. Some waves penetrate and pass entirely through it into space, never to return. Other waves penetrate but bend. Generally, the ionosphere acts as a conductor, and absorbs energy in varying amounts from the electronic wave. The ionosphere also acts as an electronic mirror and refracts (bends) the sky wave back to the earth, as illustrated. Here the ionosphere does by refraction what water does to a beam of light. The ability of the ionosphere to return an electronic wave to the earth depends upon the angle at which the sky wave strikes the ionosphere, the frequency of the transmissions, and ion density. When the wave from an antenna strikes the ionosphere, at an angle, the wave begins to bend. If the frequency and angle are correct and the ionosphere is sufficiently dense, the wave will eventually emerge from the ionosphere and return to the earth. If a receiver is located at either of the points B, the transmission from point A will be received. The sky wave on the next page is assumed to be composed of rays that emanate from the antenna in three distinct groups that are identified according to the angle of elevation: The angle at which the group 1 rays strike the ionosphere is too nearly vertical for the rays to be returned to earth. The rays are bent out of line, but pass completely through the ionosphere and are lost. A currently popular theory on propagation is explained as follows. The angle made by the group 2 rays is called the CRITICAL ANGLE for that frequency. Any ray that leaves the antenna at an angle greater than this angle (θ) will penetrate the ionosphere. Group 3 rays strike the ionosphere at the smallest angle that will be refracted and still return to the earth. At any smaller angle the rays will be refracted but will not return to the earth. FOR TRAINING PURPOSES ONLY! As the frequency increases, the initial angle decreases. Low frequency fields can be projected straight upward and will be returned to the earth. The highest frequency that can be send directly upward and still be refracted back to the earth is called the CRITICAL FREQUENCY. At sufficiently high frequencies, regardless of the angle at which the rays strike the ionosphere, the wave will not be returned to the earth. The critical frequency is not constant but varies from one locality to another, with the time of day, with the season of the year, and with the sunspot cycle. HAM US/O-53 KrA Mar 08, 2017 10|IONSPH Effects|L3|B2 Page 28 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Ionosperic Effects Effect of Ionosphere on the Sky Wave Because of this variation in the critical frequency, nomograms and frequency tables are issued that predict the Maximum Usable Frequency (MUF) for every hour of the day for every locality in which transmissions are made. Nomograms and frequency tables are prepared from data obtained experimentally from stations scattered all over the world. All this information is pooled, and the results are tabulated in the form of long range predictions that remove some of the guesswork from transmissions. Skip Zone (Dead Zone) Between the point where the ground wave is completely dissipated and the point where the first sky wave returns, no signals will be heard. This area is called the SKIP ZONE, and is illustrated on the next page. The skip zone for the lower high frequencies (3 to 9 MHz) will be greater at night than during the day. However, skip effects can be minimized by utilizing lower frequencies for nighttime communication. As a general rule, it can be said that as the frequency decreases, the skip distance decreases. Multiple−Hop Transmission FOR TRAINING PURPOSES ONLY! In some cases, multiple reflections can occur. Signals may be reflected by the ionosphere, return to the ground where they are also reflected and return to the ionosprere where they are reflected again,. Fading Multiple-Hop may cause fading in case transmission with a different amount of reflections superpose with different phases. HAM US/O-53 KrA Mar 08, 2017 10|IONSPH Effects|L3|B2 Page 28 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 Sky Wave Ionosphere Antenna Ground Wave A Skip Zone B Skip Distance FOR TRAINING PURPOSES ONLY! Figure 14 Sky Wave Propagation HAM US/O-53 KrA Mar 08, 2017 10|IONSPH Effects|L3|B2 Page 29 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Radio Technology M13.4 FOR TRAINING PURPOSES ONLY! Figure 14 Sky Wave Propagation HAM US/O-53 KrA Mar 08, 2017 10|IONSPH Effects|L3|B2 Page 29 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66 M13 AVIONIC SYSTEMS (ATA 23) Antennas M13.4 ANTENNAS Antenna Introduction Antenna Function An antenna is a type of wave transformer for transporting line bundled electromagnetic energy into free radiation energy (transmission antenna) or vice versa (receiver antenna). It therefore represents the link between transmitter and receiver. As transmission and reception antennae can electrically be dealt with the same way, the antenna theory will be explained from a transmitter antenna example. Mechanical differences between transmission and reception antennas are necessary due to varying high transmission power. The antenna’s shape i. e. the antenna system results from whatever use it is put to. Important criteria for the choice are: Frequency range, Band width, Propagation characteristic, Polarization. FOR TRAINING PURPOSES ONLY! An exact calculation for antennae is seldom possible, as surrounding influences can strongly influence the antennae size, so as the antenna is quite often experimentally determined. HAM US/O-53 KrA Mar 13, 2017 01|INTRO|L1|AB12 Page 30 Lufthansa Technical Training AIRCRAFT SYSTEMS EASA PART-66