Chapter 2 Radio and Electronics Fundamentals

1. Chapter 2 Radio and Electronics Fundamentals 2.1 Equipment Definitions 2.2 Electricity 2.3 Components & Units 2.4 Signals and Waves 2.5 Antennas & Feedlines 2.6 Propagation

2. 2.1 EQUIPMENT DEFINITIONS

3. Basic Station Organization

4. Station Basics

5. Accessory Radio Equipment Microphone converts voice into audio The transmitter then adds the audio to the signal Speakers turn electrical audio back into sound Headphones are used in place of speakers Good in noisy environments Amplifiers increase the strength of a signal Preamplifiers amplify received radio signals Power Amplifiers ('linears') increase transmitted signals

6. 2.2 Electricity

8. CURRENT (I) Current is the flow of electrons Measured in AMPERES or AMPS Good Conductors – metal -gold,silver,copper Insulators – glass, plastic, rubber 1/1000th AMP = 1 milliampere 1/1000,000th AMP = 1 microampere The French word for current is 'Intensite' so AMPS are abbreviated 'I' AMPS are measured with an AMMETER

9. VOLTAGE (E) ELECTROMOTIVE FORCE (EMF) is the pressure behind the electrons EMF is measured in VOLTS 1,000 Volts is a KILOVOLT 1,000,000 Volts is a MEGAVOLT VOLTAGE is measured with a VOLTMETER Voltage has polarity – positive or negative Positive voltage attracts electrons Negative voltage repels electrons The abbreviation for VOLTS is 'E'

14. GROUND Earth's surface is a universal reference for voltage measurements GROUND POTENTIAL or just 'GROUND'

15. AC and DC Current that flows in one direction is DIRECT CURRENT or DC Comes from batteries, solar cells Current that reverses direction regularly is ALTERNATING CURRENT or AC Comes from alternators, dynamos A voltage that has the same polarity all the time is DC VOLTAGE Car batteries 12 Volts , flashlight batteries 1.5V A voltage that reverses polarity regularly is AC VOLTAGE

16. AC on an Oscilloscope

17. 17 Reactance and Impedance Resistance to AC current flow is REACTANCE In capacitors and inductors, the current and voltage are out of phase Capacitors and inductors operate opposite one another in terms of reactance Capacitive reactance Inductive reactance Impedance is the combination of reactance and DC resistance

18. Circuits A circuit is a complete path for current A SHORT CIRCUIT is an unintentional connection between two points in a circuit An OPEN CIRCUIT is one with no path for the current

19. 2.3 Components and Units

22. Resistors Provide resistance (ohms) in a circuit Are made from a number of materials Wirewound Carbon Film Can be fixed or variable Variable resistors are called 'potentiometers' or 'pots' and are often used as volume controls

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25. 25 Protective Components Fuses protect circuits from excess current Melt a piece of metal to break the circuit Protects from OVERLOADS Circuit Breakers sense an overcurrent condition and open the circuit Surge Suppressors limit temporary spikes of voltage by increasing the resistance VERY important here in lightning land!!!

26. 26 2.4 Signals and Waves

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29. 29 RF Spectrum Signals above 20,000 Hz (20 Khz) are RADIO FREQUENCY Signals below 20,000 Hz are AUDIO FREQUENCY (voice 300-3000 Hz.) Signals above 1 Ghz (1,000 Mhz) are MICROWAVES Frequencies used by amateurs are the amateur bands or “ham bands”

30. 30 HF Spectrum VLF 3 – 30 Khz LF 30 – 300 Khz MF 300 Khz – 3 Mhz HF 3 Mhz – 30 Mhz VHF 30 Mhz - 300 Mhz UHF 300Mhz - 3 Ghz SHF 3 Ghz – 30 Ghz EHF 30 Ghz – 300 Ghz

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33. 33 Amateur Microwave Bands 13 cm (2.4 Ghz.) 9 cm (3.3 Ghz.) 5 cm (5.65 Ghz) 3 cm (10 Ghz.) 1.25 cm (24 Ghz) 6.3 mm (47 Ghz.) 3.8 mm (75.5 Ghz.) 2 mm (142 Ghz.) 1.2 mm (241 Ghz.) < 1mm (>300 Ghz.)

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41. 41 Fast Scan TV Bandwidth = 6 Mhz.

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43. 43 2.5 Antennas & Feedlines

44. 44 Feed Line Characteristic Impedance Impedance is a form of opposition to an alternating current or RF current Maximum power is provided when the transmitter output impedance matches the characteristic impedance of the feed line and the antenna. Typical transmitter output and feed line impedance value is 50 ohms. Antenna tuners are used to match transmitter output and antenna impedances.

45. 45 Feed Line Types

46. 46 Feed Lines Coaxial Cable Contains a center wire inside an insulating material covered by a metal sleeve or wire shield. Most common types have characteristic impedances of 50 or 75 ohms. Coaxial cable is an unbalanced feed line. Poor quality coaxial cable can result in transmitter power loss as heat. Larger diameter cables tend to have lower losses. High SWR causes losses in the cable

47. 47 Coaxial Connectors

48. 48 Standing Wave Ratio (SWR) Power travelling from the transmitter to the antenna is called forward power. Power that returns to the transmitter from the antenna is called reflected power A perfect SWR is 1:1, this means The antenna load (impedance) is matched to the transmitter There is NO reflected power Measured with SWR Bridge or Directional Wattmeter Transmitters reduce power output above 2:1 SWR

49. 49 SWR Meters Usually connected between transmitter output and antenna feed line to measure SWR. An antenna tuner can be used to adjust the SWR reading close to the optimum value 1:1. The antenna tuner should be connected between the antenna and SWR meter.

50. 50 Standing Wave Ratio (SWR)

51. 51 Wattmeters Connected to the transmission line to measure power (in watts) from the transmitter. A directional wattmeter measures both forward power and reflected power.

52. 52 Practical Antennas Half-Wave Dipole Multi-band dipole Quarter-wavelength vertical HF VHF/UHF Antennas for Hand-held Transceivers Beam Antennas Yagi Cubical Quad Delta Loop

53. 53 Half-Wave Dipole Antenna Wire antenna with a total length of ½ ? with the feed line connected at the center point. Total antenna length (in feet) is given as: Dipole resonate frequency can be changed by adjusting the antenna wire length. Increase length to reduce resonate frequency Decrease length to increase resonate frequency

54. 54 Half-Wavelength Dipole Antenna

55. 55 Quarter-Wavelength Vertical Antennas Vertical antennas are nondirectional or omnidirectional antennas that radiate energy in all compass directions. Tend to concentrate signals toward the horizon (low-angle of radiation). Do not generally radiate signals straight up. Provide gain when compared to a dipole antenna. Vertical antenna ¼? radiator length:

56. 56 Vertical Antennas

57. 57 Quarter-Wavelength Vertical Antennas HF vertical antennas require ground plane radials for proper operation. VHF/UHF verticals for mobile operation use the metal car body as a ground plane. A 5/8? vertical antenna provides gain over a ¼? vertical antenna Concentrates more signal at the horizon Contains an impedance matching device at the antenna feed point Some vertical antennas contain tuned traps that change the electrical length of the antenna to work on multiple bands. 

58. 58 Antennas for Hand-Held Transceivers The rubber duck is the most common antenna used with a hand-held transceiver. Antenna is inexpensive, small, lightweight and difficult to break Is a compromise design that does not perform as well as larger antennas. An external vertical antenna on a car exterior will always outperform a rubber duck antenna inside the car.

59. 59 Antenna Polarization Polarization refers to electric-field orientation of a radio wave. Vertical polarization when the elements are perpendicular to the ground Horizontal polarization when the elements are parallel to the ground Most VHF/UHF FM stations and repeaters use antennas with vertical polarization. Weak signal modes on VHF/UHF, like SSB use antennas with horizontal polarization.

60. 60 Antenna Polarization

61. 61 Beam Antennas Beams are directional antennas used on the higher frequency HF bands and also on VHF/UHF bands. Beam antennas provide transmit gain and receive selectivity in the direction they are pointed A Yagi antenna is a common beam antenna.

62. 62 Beam Radiation Patterns

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64. 64 Yagi Beam Antenna

65. 65 Other Types of Beam Antennas Cubical Quad A wire antenna usually containing 1? driven and reflector elements mounted on a boom. The wire elements are usually arranged in a square. Radiation pattern is similar to a Yagi antenna. Polarization can be changed by changing the antenna feed point on the driven element. Parabolic Dish

66. 66 Other Types of Beam Antennas

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68. 68 2.6 – Propagation Propagation: How Signals Travel Propagation On The HF Bands Ground-wave Propagation Sky-wave Propagation HF Scatter Propagation VHF/UHF Propagation Characteristics Line-of-sight Propagation Tropospheric Bending and Ducting VHF/UHF Signals Through The Ionosphere

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70. 70 Atmospheric Regions

71. 71 Atmospheric Regions

72. 72 HF Band Propagation Ground-Wave Propagation Sky-wave Propagation HF Scatter Mode

73. 73 Ground-Wave Propagation Results from a radio wave diffraction along the Earth’s surface. Primarily affects longer wavelength radio waves that have vertical polarization (electric field is oriented vertically). Most noticeable on AM broadcast band and the 160 meter and 80 meter amateur bands. Communication distances often extend to 120 miles or more. Most useful during the day at 1.8 MHz and 3.5 MHz when the D-Region absorption makes sky-wave propagation impossible.

74. 74 Ground-Wave Propagation

75. 75 Sky-wave Propagation Ionization levels in the Earth’s ionosphere can refract (bend) radio waves to return to the surface. Ions in the Earth’s upper atmosphere are formed when ultraviolet (UV) radiation and other radiation from the sun knocks electrons from gas atoms. The ionization regions in the Earth’s ionosphere is affected the sunspots on the sun’s surface. The sunspots vary in number and size over a 11 year cycle. Sky-wave propagation is determined by radio wave frequency and level of ionization in the ionosphere.

76. 76 Sky-wave Propagation (Cont’d) Communication distances of 2500 miles are possible with one skip off the ionosphere. Skip propagation has both minimum and maximum ranges. The area between the maximum ground wave distance and the minimum skip distance is called the skip zone. World-wide communications is possible using several skips (or multi-hops) Usually, VHF signals are not reflected back to Earth by the ionosphere

77. 77 Sky-wave Propagation (Cont’d) The maximum usable frequency (MUF) is the highest frequency at which the ionosphere bends radio waves back to a desired location on earth. MUF is dependant on level of solar radiation strength and time of day. The maximum usable frequency (MUF) tends to be higher during periods of high sunspots.

78. 78 Sky Wave Propagation

79. 79 Regions In The Ionosphere

80. 80 VHF/UHF Propagation Line Of Sight (LOS) Tropospheric Bending Tropospheric Ducting VHF/UHF Signals Through The Ionosphere Sporadic “E”

81. 81 Line-Of-Sight Propagation Radio signals travel in a straight line from a transmitting antenna to the receiving antenna. Provides VHF/UHF communications within a 100 miles or so. Signals can be reflected by buildings, hills, airplanes, etc. Reflections vary the propagation path causing signal cancellation and reinforcement. This results in a rapid fluttering sound called picket fencing. UHF signals often penetrate better into buildings

82. 82 Line-Of-Sight (LOS) Propagation

83. 83 Tropospheric Bending Slight bending of radio waves occur in the troposphere close to the Earth’s surface. There is always a radio signal loss as radio waves travel through the troposphere Radio signal loss increases as the frequency increases The radio path horizon is generally 15 percent farther away than the visible horizon (typically 8 to 9 miles). Communication distances can be increased by increasing the antenna height above the terrain Tropospheric bending propagation is most useful at 144 Mhz and higher frequencies

84. 84 Radio Path Horizon The farthest point to which radio waves will travel directly. The structure of the atmosphere near the Earth’s surface causes the radio waves to bend in a curved path. The radio horizon exceeds the geometric horizon by approximately 15%.

85. 85 Radio Path Horizon

86. 86 Tropospheric Ducting Radio signals can also be trapped in the troposphere, traveling a long distance before returning to the Earth’s surface. Results when a “duct” is formed by a temperature inversion level (warm air over cold air) over land or water. Adjacent tropospheric regions having different densities will bend radio waves passing through the regions Most useful at VHF/UHF frequencies. Most frequent during spring, summer and fall. Can provide contacts of 950 miles or more over land and up to 2500 miles over ocean

87. 87 Tropospheric Ducting

88. 88 VHF/UHF Signals Through Ionosphere Sporadic E A type of sky-wave propagation that allows long distance communication on the VHF bands (6 meters, 2 meters and 220 Mhz) through the E region of the atmosphere. Most common type of VHF atmospheric propagation. The 6 and 10 meter bands are most likely to experience sporadic-E propagation during the summer months ... even during periods of low sunspot activity.