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Amateur Radio

Amateur Radio. Radio Phenomena Wave Propagation. What we are going to cover. Topics Radio Spectrum, Licensing and Methods (09/22) T1,T2,T7A/B Radio Phenomena (09/29) T3 Station Licensee and Control Op Duties (10/06) T4,T5

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Amateur Radio

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  1. Amateur Radio Radio Phenomena Wave Propagation

  2. What we are going to cover. • Topics • Radio Spectrum, Licensing and Methods (09/22) T1,T2,T7A/B • Radio Phenomena (09/29) T3 • Station Licensee and Control Op Duties (10/06) T4,T5 • Good Operating Practices, Special Ops (10/13) T6,T9 • Basic Electronics (10/20) T7 • Good Engineering Practices (10/27) T8 • Electrical, Antennas and RF Safety (11/03) T0 • Review/Practice (11/10) All • Home Study • Reading Assignments • Home Work • Morse Code • Test • Nov 17th

  3. Missed Items from T2 Sorry…

  4. T2A13 What is the basic principle of radio communications? • A. A radio wave is combined with an information signal and is transmitted; a receiver separates the two • B. A transmitter separates information to be received from a radio wave • C. A DC generator combines some type of information into a carrier wave so that it may travel through space • D. The peak-to-peak voltage of a transmitter is varied by the sidetone and modulated by the receiver

  5. T2A13 What is the basic principle of radio communications? • A. A radio wave is combined with an information signal and is transmitted; a receiver separates the two • B. A transmitter separates information to be received from a radio wave • C. A DC generator combines some type of information into a carrier wave so that it may travel through space • D. The peak-to-peak voltage of a transmitter is varied by the sidetone and modulated by the receiver

  6. Harmonics • Integer Multiple of a frequency • 1st = 1*f0 - Fundamental Frequency • 2nd = 2*f0 • 3rd = 3*f0 • 4th = 4*f0 • nth = n*f0

  7. T2A02 How does the frequency of a harmonic compare to the desired transmitting frequency? • A. It is slightly more than the desired frequency • B. It is slightly less than the desired frequency • C. It is exactly two, or three, or more times the desired frequency • D. It is much less than the desired frequency

  8. T2A02 How does the frequency of a harmonic compare to the desired transmitting frequency? • A. It is slightly more than the desired frequency • B. It is slightly less than the desired frequency • C. It is exactly two, or three, or more times the desired frequency • D. It is much less than the desired frequency

  9. T2A05 What is the fourth harmonic of a 50.25 MHz signal? • A. 201.00 MHz • B. 150.75 MHz • C. 251.50 MHz • D. 12.56 MHz

  10. T2A05 What is the fourth harmonic of a 50.25 MHz signal? • A. 201.00 MHz • B. 150.75 MHz • C. 251.50 MHz • D. 12.56 MHz

  11. CW – 5-10Hz Phone/ Voice SSB - 2-3KHz AM – 4-6KHz FM – 10-20KHz Digital PSK31 – 31 Hz RTTY – 500 Hz Fast Scan TV – 6Mhz Slow Scan TV – 3KHz Common required Bandwidth

  12. T2B17 What is the typical bandwidth of PSK31 digital communications? • A. 500 kHz • B. 31 Hz • C. 5 MHz • D. 600 kHz

  13. T2B17 What is the typical bandwidth of PSK31 digital communications? • A. 500 kHz • B. 31 Hz • C. 5 MHz • D. 600 kHz

  14. Wave Propagation Fun Stuff

  15. T3 - Radio Phenomena[2 Exam Questions - 2 Groups] • T3A How a radio signal travels; Atmosphere/troposphere/ionosphere and ionized layers; Skip distance; Ground (surface)/sky (space) waves; Single/multihop; Path; Ionospheric absorption; Refraction. • T3B HF vs. VHF vs. UHF characteristics; Types of VHF-UHF propagation; Daylight and seasonal variations; Tropospheric ducting; Line of sight; Maximum usable frequency (MUF); Sunspots and sunspot Cycle, Characteristics of different bands.

  16. Wave Propagation Paths/Loss • Polarization • Path Loss – Field Strength • Reflection • Refraction • Diffraction • Interference

  17. Electric/Magnetic Field Orientation (Polarization) Electromagnetic waves are disturbances to the electrical and magnetic fields. A changing electric disturbance produces a changing magnetic field at right angles to the electric field.

  18. Field Strength and Path Loss • Spreading - energy distributed over an increasingly larger area. Energy per unit area proportional to 1/R2. • Absorption - energy dissipated into medium. Molecules of medium absorb some of the energy as it passes through. • Scattering - energy bouncing off suspended particles within a medium • Friis’s Formula

  19. Media boundaries with dissimilar propagation result in reflection. Angle of incidence = Angle of reflection Diffuse reflection results from waves striking an irregular surface and reflecting over a broad range of angles Specular reflection is reflected at equal but opposite angle from smooth surface. Diffuse Specular …Reflection…

  20. Snell’s Law n1 sinq1 = n2 sinq2 …Refraction… Incident wave passes through two transparent media in which the velocity of light differs... Not all wave is reflected. Some is transmitted into medium interface at some angle. This angle can be determined using Snell’s Law. Bending of the signal by atmosphere decreases with increasing frequency Bending of the signal by atmosphere increases with increasing ionization • Electromagnetic waves propagate at speed of light (c) • Speed of light varies in different medium (C0) • Light refracts at the boundary layer. • Index of refraction, n, defined as; n = C/C0

  21. Diffraction – the appearance of wave bending around an object because of different speeds of wavelet at medium interface. Can detect signals in spite of LOS limitations.  = 2/L (in radians)

  22. Interference – when two or more waves meet, amplitudes add to produce a new wave. Can be described as either constructive or destructive interference, depending on phase shift between waves. Constructive – phase difference between 0o and 120o or between 240o and 360o . • Destructive – phase difference between 120o and 240o .

  23. Atmosphere The Air Around Us

  24. A,B,C – (1st 50KM) D layer: height approx. 60-90 km (25-55mi) E layer: height approx. 90-150 km (55-90mi) F1 layer: height approx. 150-250 km (90-150mi) F2 layer: height approx. 250-500 km (>250mi) D, E layers disappear at night F layers combine into one at night Atmospheric Layers

  25. Ionospheric Protection The ionosphere and magnetosphere protect us from harmful radiation from the sun

  26. Ionospheric Layers • D – Low Ionization • Absorbs (Attenuates) MF and HF range • Amount of absorption is dependent on ionization • Disappears at night • E- Less Ionized than F • Refracts RF signals • Absorbs MF and HF • Disappears at night • F – Hi Ionization • layer acts as a reflector of signals in the HF range • Two layers during the day • Ionization is higher at equator

  27. Sunspots • Sunspots peak during 11-year cycles • The higher the sunspot count, the more the atmosphere is ionized • Thus, higher sunspot counts support a higher Maximum Usable Frequency (MUF) • The Higher the Ionization the more absorption

  28. Wave Propagation … • Propagation Modes • Ground Waves (Direct) • Isotropic (Sky) Waves (Reflected) • Space Waves

  29. Waves follow the curvature of earth Range varies with frequency (low frequencies go further) range varies from worldwide at 100 kHz and less to about 100 km at AM broadcast band frequencies (approx. 1 MHz) Direct Path Ground-Wave Propagation

  30. Useful mainly in HF range (3-30 MHz) Signals are refracted in ionosphere and returned to earth Worldwide communication is possible using multiple “hops” More ionization causes signals to bend more Ionization caused by solar radiation greater during daytime greater during sunspot cycle peaks (we are about at a decreasing value now-2004) Ionospheric PropagationSkyWaves

  31. Skip Zone Region between maximum ground-wave distance and closest point where sky waves are returned from the ionosphere Ionospheric Propagation

  32. Ionospheric Sounding Transmit signal straight up Note the maximum frequency that is returned This is the critical frequency Important Frequencies Critical frequency Highest frequency that is returned to transmitter Maximum Usable Frequency (MUF) Highest frequency that is returned at a given point Optimum Working Frequency (OWF) 85% of MUF for more reliable communication Ionospheric Propagation

  33. Higher frequency signals that penetrate the ionosphere and travel through space. Above 30 MHz, ionosphere will not refract E-M waves back toward earth. Energy tends to travel in straight line. Frequencies above Critical Frequency Space Wave...

  34. Tropospheric Bending • Line of Sight (LOS) MAX RANGE is increased due to ducting, certain electromagnetic waves can transmit farther than the “visual” Line of Sight (LOS). • ~5’ -> ~5Km, ~10’ -> 7Km, 15’ -> ~ 8.8Km • 228th and 45th -> ~48Km (30mi) D = Distance (in Km) h = Antenna height above ground (m) Visual Horizon

  35. Tropospheric Ducting Sporadic E • usually caused by a temperature inversion or ionization in “E” layer (Sporadic E) • Enables long range VHF and UHF communications • Mostly effects 6 meters

  36. Band summary of Propagation Modes

  37. T3A02 Which ionospheric region is closest to the Earth? • A. The A region • B. The D region • C. The E region • D. The F region

  38. T3A02 Which ionospheric region is closest to the Earth? • A. The A region • B. The D region • C. The E region • D. The F region

  39. T3B09 Which of the following frequency bands is most likely to experience summertime sporadic-E propagation? • A. 23 centimeters • B. 6 meters • C. 70 centimeters • D. 1.25 meters

  40. T3B09 Which of the following frequency bands is most likely to experience summertime sporadic-E propagation? • A. 23 centimeters • B. 6 meters • C. 70 centimeters • D. 1.25 meters

  41. T3B11 What is the condition of the ionosphere above a particular area of the Earth just before local sunrise? • A. Atmospheric attenuation is at a maximum • B. The D region is above the E region • C. The E region is above the F region • D. Ionization is at a minimum

  42. T3B11 What is the condition of the ionosphere above a particular area of the Earth just before local sunrise? • A. Atmospheric attenuation is at a maximum • B. The D region is above the E region • C. The E region is above the F region • D. Ionization is at a minimum

  43. T3B13 In relation to sky-wave propagation, what does the term "maximum usable frequency" (MUF) mean? • A. The highest frequency signal that will reach its intended destination • B. The lowest frequency signal that will reach its intended destination • C. The highest frequency signal that is most absorbed by the ionosphere • D. The lowest frequency signal that is most absorbed by the ionosphere

  44. T3B13 In relation to sky-wave propagation, what does the term "maximum usable frequency" (MUF) mean? • A. The highest frequency signal that will reach its intended destination • B. The lowest frequency signal that will reach its intended destination • C. The highest frequency signal that is most absorbed by the ionosphere • D. The lowest frequency signal that is most absorbed by the ionosphere

  45. Backup Slides

  46. Electromagnetic Radiation • Includes radio waves, light, X-rays, gamma rays Radio waves of our interest VLF 3 – 30 kHz LF 30 – 300 kHz MF 300 – 3000 kHz HF 3 – 30 MHz VHF 30 – 300 MHz UHF 300 – 3000 MHz

  47. Agenda for today • Electromagnetic Waves • Objectives • Define some terms • Electric fields, Magnetic fields, propagation of electromagnetic waves, and losses • Wave Propagation • Objectives • Reflection, Refraction, Diffraction. and Snell’s Law. • Interference on EM waves and Phase Angle. • Propagation Paths • Ground Waves, Sky Waves, and Space Waves • Max Range equation to determine the maximum distance between a target and a sensor

  48. Electromagnetic Wave • Wave - Localized disturbance in medium which effects neighboring portion of medium, and so on, and so on… • Sinusoidal in nature • Two major types • Longitudinal – Disturbance in line with direction of propagation (Sound) • Transverse – Disturbance at right angle to direction of propagation. (Electromagnetic, TEM)

  49. Spherical Wave Close to source Undisturbed wave Omni directional from source Ripples on a pond. Plane Wave Far from origin Spreads out to appear to have same amplitude everywhere on plane ┴ to direction of travel Think of entire wave traveling in one direction Power Density  1/r2 Wave Propagation

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