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Radio Signals and Waves: Fundamentals and Concepts

Learn about the basics of radio signals and waves, including their frequency, amplitude, harmonics, and conversion within the metric system.

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Radio Signals and Waves: Fundamentals and Concepts

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  1. Chapter 2 Radio and Signals Fundamentals

  2. Radio and Signal Fundamentals Radio Signals and Waves • 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. 7/1/2014 - 6/30/2018 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”. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  4. Radio and Signal Fundamentals Radio Signals and Waves 7/1/2014 - 6/30/2018 Technician - Chapter 2

  5. 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) 7/1/2014 - 6/30/2018 Technician - Chapter 2

  6. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  7. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  8. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  9. 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 = .000001 --- 1 volt ÷ 1,000,000 = a millionth of a volt 7/1/2014 - 6/30/2018 Technician - Chapter 2

  10. 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 ÷ 1/1000 = 0.5 watts 7/1/2014 - 6/30/2018 Technician - Chapter 2

  11. 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 = 1/1000 • 3000 mA ÷ 1000 = 3 amperes or “amps” 7/1/2014 - 6/30/2018 Technician - Chapter 2

  12. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  13. 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 ÷ 1/1,000,000 = 1 microfarad 7/1/2014 - 6/30/2018 Technician - Chapter 2

  14. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  15. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  16. Radio and Signal Fundamentals Radio Signals and Waves • 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” 7/1/2014 - 6/30/2018 Technician - Chapter 2

  17. Radio and Signal Fundamentals Radio Signals and Waves Harmonics 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”. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  18. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  19. 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 ovens operate at 2.4 GHz Hams primarily use frequencies in the Middle Frequency (MF) through Ultra High Frequency (UHF) and microwave ranges. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  20. Radio and Signal Fundamentals Radio Signals and Waves 7/1/2014 - 6/30/2018 Technician - Chapter 2

  21. 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” 7/1/2014 - 6/30/2018 Technician - Chapter 2

  22. 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) = 7/1/2014 - 6/30/2018 Technician - Chapter 2

  23. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  24. Radio and Signal Fundamentals Modulation • 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  25. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  26. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  27. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  28. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  29. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  30. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  31. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  32. 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 7/1/2014 - 6/30/2018 Technician - Chapter 2

  33. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  34. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  35. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  36. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  37. Radioand 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 your 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  38. 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. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  39. Radio and Signal Fundamentals Modulation Phase Modulation Most hams refer to either FM or PM signals as FM 7/1/2014 - 6/30/2018 Technician - Chapter 2

  40. Radio and Signal Fundamentals Modulation What are the different types of modulation and signals available? How do you choose one over the other? What are the strengths and weaknesses of each What makes on better than another? 7/1/2014 - 6/30/2018 Technician - Chapter 2

  41. Radio and Signal Fundamentals Modulation Unfortunately, the AM signals are subject to all the noise while the FM signals are static-free. For short-range and regional communications, the lower noise of FM signals clearly outweigh any considerations about bandwidth. FM can also be used for data signals, such as those for “packet radio” on VHF and UHF. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  42. Radio and Signal Fundamentals Modulation Even though FM may proved a better quality signal, SSB is often used where signals are weaker and where the spectrum will not support a large number of FM users. Signals on the HF bands below 30 MHz are almost exclusively SSB or CW. SSB signals use much less bandwidth than FM or digital signals. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  43. Radio and Signal Fundamentals Modulation 7/1/2014 - 6/30/2018 Technician - Chapter 2

  44. Radio and Signal Fundamentals Modulation Because the SSB power is concentrated into a narrow bandwidth, it is possible to communicate over much longer distances and in poorer conditions compared to FM or AM, particularly on the VHF and UHF bands. That’s why the VHF and UHF “Dxers” and contest operators use SSB. For even better range, extremely narrow CW signals are the easiest for a human operator to send and receive, especially in noisy or fading conditions. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  45. Radio and Signal Fundamentals Modulation • Upper sideband or lower sideband – which to use? • It doesn’t matter as long as both stations are using the same sideband. Otherwise it won’t work. • Ham radio operators and manufacturers have agreed upon a standard: • Above 10 MHz – USB is used including all of the VHF and UHF bands. • Below 10 MHz – LSB is used EXCEPT on the 60m band where you are REQUIRED to use USB. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  46. Radio and Signal Fundamentals Radio Equipment Basics 7/1/2014 - 6/30/2018 Technician - Chapter 2

  47. Radio and Signal Fundamentals Radio Equipment Basics A repeater is a station that transmits a received signal simultaneously on another frequency or channel. Repeaters provide local and regional communications between low-power mobile and portable stations. The job of the repeater is to provide a strong, low-noise signal that everyone can hear and understand well, especially during emergencies. 7/1/2014 - 6/30/2018 Technician - Chapter 2

  48. Radio and Signal Fundamentals Radio Equipment Basics A simple repeater Transmitted signal out Received signal in Transmitter Duplexer Receiver Speech from received signal 7/1/2014 - 6/30/2018 Technician - Chapter 2

  49. Radio and Signal Fundamentals Radio Equipment Basics Input Freq 147.765 MHz Output Freq 147.165 MHz Offset + 600 kHz 50-60 miles Listen on 147.165+ MHz Transmit on 147.765 MHz 7/1/2014 - 6/30/2018 Technician - Chapter 2

  50. Radio and Signal Fundamentals Radio Equipment Basics Accessories 7/1/2014 - 6/30/2018 Technician - Chapter 2

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