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Chapter 2

Chapter 2. Radio and Signals Fundamentals. Radio and Signal Fundamentals Radio Signals and Waves. Signals travel back and forth between radios carrying voices, data and Morse code. Radio waves that travel at the speed of light .

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Chapter 2

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  1. Chapter 2 Radio and Signals Fundamentals

  2. Radio and Signal Fundamentals Radio Signals and Waves • Signals travel back and forth between radios carrying voices, data and Morse code. • Radio waves that travel at the speed of light. • Radio waves start as an electrical signal in an antenna that constantly changes direction. • The rate of change determines the signal’s frequency. • The radio wave travels away from the antenna into space, vibrating or oscillating at the same frequency as the electrical signal. 2010 Technician - Chapter 2

  3. Radio and Signal Fundamentals Radio Signals and Waves • As the radio wave passes other antennas, it creates replicas of the original electrical signal. • A radio converts the signal back into a voice, digital data or even Morse code. • The process of turning the transmitter output signal into radio waves that leave the antenna is called “radiation” or “radiating”. • The radio wave travels away from the antenna into space, vibrating or oscillating at the same frequency as the electrical signal. 2010 Technician - Chapter 2

  4. Radio and Signal Fundamentals Radio Signals and Waves • All radio equipment is designed to generate or manipulate radio signals. • No matter how you communicate by ham radio --- with voice, Morse code or computer --- those resulting radio signals are usually referred to as just signals. 2010 Technician - Chapter 2

  5. Radio and Signal Fundamentals Radio Signals and Waves 2010 Technician - Chapter 2

  6. Radio and Signal Fundamentals Radio Signals and Waves • As frequency increases, it becomes easier to use units of--- • kilohertz (1kHz = 1,000 Hz) • megahertz (1 MHz = 1,000 kHz or 1,000,000 Hz) and • gigahertz (1 GHz = 1,000 MHz or 1,000,000,000 Hz) 2010 Technician - Chapter 2

  7. Radio and Signal Fundamentals Radio Signals and Waves • Metric conversions within the Metric System • 1.5 amperes = How many Milliamperes? • 1,500 milliamperes • 1.5 x 1,000 = 1,500 2010 Technician - Chapter 2

  8. Radio and Signal Fundamentals Radio Signals and Waves • Metric conversions within the Metric System • 1,500,000 hertz can be specified in what other ways? • 1,500 kilohertz or 1.5 Megahertz • 1,500,000 divided by 1,000 = 1500 kHz • 1,500,000 divided by 1,000,000 = 1.5 MHz 2010 Technician - Chapter 2

  9. Radio and Signal Fundamentals Radio Signals and Waves • Metric conversions within the Metric System • How many volts equal a kilovolt? • 1,000 volts • Kilo = 1000 --- 1 volt x 1,000 = a kilovolt 2010 Technician - Chapter 2

  10. Radio and Signal Fundamentals Radio Signals and Waves • Metric conversions within the Metric System • How many volts equal a microvolt? • A millionth of a volt • Micro = 1,000,000 --- 1 volt ÷ 1,000,000 = a millionth of a volt 2010 Technician - Chapter 2

  11. Radio and Signal Fundamentals Radio Signals and Waves • Metric conversions within the Metric System • 500 milliwatts is equal to what? • 0.5 Watts or one-half watt • milli equals one thousandth • 500 milliwatts ÷ 1000 = 0.5 watts 2010 Technician - Chapter 2

  12. Radio and Signal Fundamentals Radio Signals and Waves • Metric conversions within the Metric System • If an ammeter calibrated in amperes is used to measure a 3000-milliampere circuit what would be the reading? • 3 amperes • Milli = 1000 • 3000 mA ÷ 1000 = 3 amperes or “amps” or • 0.003 A x 1000 = 3 amps 2010 Technician - Chapter 2

  13. Radio and Signal Fundamentals Radio Signals and Waves • Metric conversions within the Metric System • 3.525 MHz = How many kilohertz? • 3525 kilohertz • Kilo = 1000 • 3.525 x 1000 = 3525 kHz 2010 Technician - Chapter 2

  14. Radio and Signal Fundamentals Radio Signals and Waves • Metric conversions within the Metric System • How many microfarads equal 1,000,000 picofarads? • 1 microfarad • A microfarad = one millionth of a farad • 1,000,000 picofarads ÷ 1,000,000 = 1 microfarad 2010 Technician - Chapter 2

  15. Radio and Signal Fundamentals Radio Signals and Waves As the signal oscillates, each back-and-forth sequence is called a cycle. The number of cycles per second is the signal’s frequency and is represented by the lower case “f”. The unit of measure for frequency is hertz, which is abbreviated as “Hz”. One cycle per second is one hertz or 1 Hz. 1 2 3 4 1 Second 4 Hertz or 4 Hz 2010 Technician - Chapter 2

  16. Radio and Signal Fundamentals Radio Signals and Waves The strength or amplitude of a radio signal oscillates like a sine wave. One Cycle + 0 time - One Wavelength One Second 2010 Technician - Chapter 2

  17. Radio and Signal Fundamentals Radio Signals and Waves • The period of the cycle (represented by “T”) is its duration. The reciprocal of the period, 1/T, is the signal’s frequency, “f”. • A harmonic is a signal with a frequency that is some integer multiple (2,3,4 and so on) of a fundamental frequency. • 7.006 MHz = fundamental frequency • 14.012 MHz = second harmonic • 21.018 MHz = third harmonic • 28.024 MHz = fourth harmonic There is no “First Harmonic” 2010 Technician - Chapter 2

  18. Radio and Signal Fundamentals Radio Signals and Waves Harmonic are used to shift signal frequencies and create new signals by radio designers. These unwanted signals can also cause problems such as interference and can potentially result in signals being transmitted outside the amateur frequency bands as “spurious emissions”. 2010 Technician - Chapter 2

  19. Radio and Signal Fundamentals Radio Signals and Waves • Every cycle of the signal has the same basic shape: • Rising and falling and returning to where it started. • Position within a cycle is called “phase”. • Phase is used to compare how sine wave signals are aligned in time. • Phase is measured in degrees and there are 360 degrees in one cycle of a sine wave. 2010 Technician - Chapter 2

  20. Radio and Signal Fundamentals Radio Signals and Waves Two sine waves with a phase difference of 180 degrees so that one wave is increasing while the other is decreasing, they are “out of phase”. Waves with no phase difference (e.g., increasing and decreasing at the same time) are “in phase”. 2010 Technician - Chapter 2

  21. Radio and Signal Fundamentals Radio Signals and Waves James Clerk Maxwell predicted the existence of radio waves in 1864. Heinrich Hertz was the first to send and receive radio waves in 1886. 2010 Technician - Chapter 2

  22. Radio and Signal Fundamentals Radio Signals and Waves Signals below 20 kHz produce sound waves that humans can hear when connected to a speaker or headset. We call them audio frequency or AF signals. Signals whose frequency is greater than 20,000 Hz or 20 kHz are called radio frequency or RF signals. The range of frequencies of RF signals is called the radio spectrum. It starts at 20 kHz and goes through several hundred GHz or a thousand million times higher. 2010 Technician - Chapter 2

  23. Radio and Signal Fundamentals Radio Signals and Waves For convenience, the radio spectrum is divided into ranges of frequencies that have similar characteristics. Frequencies above 1 GHz are generally considered to be microwaves. Microwave ov ens operate at 2.4 GHz Hams primarily use frequencies in the Middle Frequency (MF) through Ultra High Frequency (UHF) and microwave ranges. 2010 Technician - Chapter 2

  24. Radio and Signal Fundamentals Radio Signals and Waves 2010 Technician - Chapter 2

  25. Radio and Signal Fundamentals Radio Signals and Waves • Specific ranges of frequencies in which signals are used for a common purpose or share similar characteristics are called “bands”. • The AM broadcast band covers 550-1700 kHz • The FM broadcast band covers 88-108 MHZ • Frequency bands used by radio amateurs are called “amateur bands” or “ham bands”. 2010 Technician - Chapter 2

  26. Radio and Signal Fundamentals Radio Signals and Waves FM Mobile Phones VHF TV UHF TV AM Shortwave 3 kHz 30 kHz 300 kHz 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz 300 GHz audio radio Some amateur portions of the RF spectrum Low Frequencies Long Wavelengths High Frequencies Short Wavelengths 2010 Technician - Chapter 2

  27. Radio and Signal Fundamentals Radio Signals and Waves The “wavelength” of a signal is the distance that it travels in during one complete cycle. It is represented by the Greek letter lambda: All radio waves travel at the speed of light which is represented by a lower-case “c”. The speed of light in space and air is 300 million meters per second or 3 x 108 meters per second. 2010 Technician - Chapter 2

  28. Radio and Signal Fundamentals Radio Signals and Waves • Radio waves are often referred to by their wavelength or frequency because the two are related by the speed of light. • You can determine the wavelength or frequency using these formulas: • Wavelength = speed of light divided by frequency • Frequency = speed of light divided by wavelength 2010 Technician - Chapter 2

  29. Radio and Signal Fundamentals Radio Signals and Waves • There are two important relationships between frequency and wavelength: • As frequency increases, wavelength decreases • As wavelength increases, frequency decreases • It is very common to refer to frequencies in the amateur bands by their wavelength as well as their frequency. • “I’ll call you on 2 meters. Let’s try 146.52 MHz” 2010 Technician - Chapter 2

  30. Radio and Signal Fundamentals Radio Signals and Waves • “I’ll call you on 2 meters. Let’s try 146.52 MHz” • In the example above, the frequency band is referred to as “2 meters” because that is approximately how long the radio waves are in that band. 300 f (in MHz) = 300 f in MHz (in meters) (in meters) = 2010 Technician - Chapter 2

  31. Radio and Signal Fundamentals Radio Signals and Waves • “I’ll call you on 2 meters. Let’s try 146.52 MHz” Determine the approximate wavelength: 300 146.52 MHz = 2.04 meters Determine the approximate frequency: 300 = 150 MHz 2 meters 2010 Technician - Chapter 2

  32. Radio and Signal Fundamentals Radio Signals and Waves Determine the approximate wavelength: 300 14.300 MHz = 20.98 meters Determine the approximate frequency: 300 = 15.0 MHz 20 meters 2010 Technician - Chapter 2

  33. Radio and Signal Fundamentals Modulation Understanding the basic concept of modulation is very important to understanding the various techniques that radio amateurs use to communicate. A simple radio signal in and of itself isn’t very useful and doesn’t do much communicating. Information must be added or contained in the radio signal. The simplest radio signal at one frequency whose strength never changes is called a “continuous wave” which we abbreviate as “CW”. 2010 Technician - Chapter 2

  34. Radio and Signal Fundamentals Modulation Adding information to a signal by modifying in some manner is called “modulation” Recovering information from a signal is called “demodulation”. The simplest type of modulation is a continuous wave that is turned on and off in a specified and distinct pattern such as Morse code. Morse code radio signals are often referred to as “CW” for that reason. 2010 Technician - Chapter 2

  35. Radio and Signal Fundamentals Modulation If we add speech to the radio signal, the result is a “phone” or “voice” mode signal. If data is added to the radio signal, the result is a “data mode” or “digital” mode signal. Analog modes carry information that can be understood directly by a human such as speech or Morse code. Digital or data modes carry information as data characters between two computers. Software in the computers converts the information into a readable form as text or pictures. 2010 Technician - Chapter 2

  36. Radio and Signal Fundamentals Modulation • Three characteristics of a signal can be modulated: • It’s amplitude or strength • It’s frequency • It’s phase • All three types of modulation are used in ham radio. 2010 Technician - Chapter 2

  37. Radio and Signal Fundamentals Modulation • You’re probably familiar with two types of modulation: • Amplitude modulation or “AM” • Frequency modulation or “FM” • You probably never gave it any thought about it but are familiar with these to modulations from you car radio or home stereo system. • Hams use variations of AM and FM plus many more types of modulation. 2010 Technician - Chapter 2

  38. Radio and Signal Fundamentals Modulation Amplitude Modulation • Turning an unmodulated signal on and off can produce Morse code characters. • Adding speech to an unmodulated signal will cause it’s amplitude or strength to vary. • The information is contained in the “envelope” of the resulting signal. 2010 Technician - Chapter 2

  39. Radio and Signal Fundamentals Modulation The receiver recovers your voice by following the signal’s amplitude variations. This process of recovering speech or music in an AM signal is called “detection” and can be performed by very simple circuits. AM is used because it is simple to transmit and receive. 2010 Technician - Chapter 2

  40. Radio and Signal Fundamentals Modulation An AM signal is composed of a carrierand two sidebands. The total power of an AM signal is divided between the carrier and two sidebands. The carrier is a continuous wave whose amplitude does not change and does not contain any information. 2010 Technician - Chapter 2

  41. Radio and Signal Fundamentals Modulation The “upper sideband” or “USB” is higher in frequency than the carrier tone. The “lower sideband” or “LSB” is lower in frequency than the carrier. 2010 Technician - Chapter 2

  42. Radio and Signal Fundamentals Modulation If the AM signal had a carrier of 800 KHz modulated by a single steady tone of 600 Hz, it would result in two sidebands each of whose width would be 600 Hz each. Both sidebands contain the information needed to reproduce the tone used to modulate the signal. 800 kHz 799.4 kHz 800.6 kHz 600 Hz 600 Hz 2010 Technician - Chapter 2

  43. Radio and Signal Fundamentals Modulation The addition of sidebands during the process of modulation causes the resulting modulated signal to be spread over a range of frequencies called the signal’s “bandwidth”. Each signal has some bandwidth. A simple CW signal requires a bandwidth of up to 150 Hz. 600 Hz 600 Hz 1200 Hz bandwidth 2010 Technician - Chapter 2

  44. Radio and Signal Fundamentals Modulation Single-Sideband (SSB) • AM signals are inefficient from the standpoint of power. • The carrier doesn’t contain information yet it takes up most of the signal power. • Each sideband contains an exact copy of the modulated signal. • A single-sideband signal is an AM signal with the carrier and one sideband removed so that all of the signal’s power is devoted to the remaining sideband. 2010 Technician - Chapter 2

  45. Radio and Signal Fundamentals Modulation An AM signal with the carrier and one sideband removed by electronic circuitry is called a single sideband (SSB) signal. 2010 Technician - Chapter 2

  46. Radio and Signal Fundamentals Modulation • The upper sideband (USB) is used on VHF and UHF. • Both USB and LSB are used on the MF and HF bands • SSB signals require more complex equipment but the improved performance is worth it. • SSB signals have a superior range because all of the power is concentrated in a single sideband. • The SSB’s bandwidth is less than 3 kHz 2010 Technician - Chapter 2

  47. Radio and Signal Fundamentals Modulation Frequency & Phase Modulation Modes that vary the frequency of a signal to add speech or data information are called frequency modulated or FM signals. Each cycle of the unmodulated carrier is the same. The signal of a frequency modulated carrier increases and decreases as the amplitude of the signal changes. 2010 Technician - Chapter 2

  48. Radio and Signal Fundamentals Modulation The frequency of an FM signal varies with the amplitude (strength) of the modulating signal. The amount of variation is called “carrier deviation” or just “deviation”. Speaking louder into the microphone of an FM transmitter increases deviation. As deviation increases, so does the signal’s bandwidth. Excessive deviation can cause interference to nearby signals. 2010 Technician - Chapter 2

  49. Radio and Signal Fundamentals Modulation Your radio displays only the carrier frequency. You must remember to leave room the signal’s sidebands. You do not want to transmit out of the amateur bands or outside of you frequency privileges. That’s illegal. If your FM voice signal is 15kHz wide, that means the sideband is the center frequency plus 7.5 kHz. Frequency. Give yourself a 10 kHz margin to be safe. 2010 Technician - Chapter 2

  50. Radio and Signal Fundamentals Modulation Phase Modulation Phase modulation or PM is similar to FM. Phase modulation varies the phase instead of the frequency. These two techniques result in signals that are approximately the same. Receivers demodulate the FM and PM signals with the same circuit. 2010 Technician - Chapter 2

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