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Radio & Signals Fundamentals

Radio & Signals Fundamentals. 2.1 – Radio Signals & Waves. System of Metric Units. Tera T 10 12 1,000,000,000,000 Giga G 10 9 1,000,000,000 Mega M 10 6 1,000,000 Kilo k 10 3 1,000 Basic Unit 10 0 1 Milli m 10 -3 0.001 Micro μ 10 -6 0.000001

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Radio & Signals Fundamentals

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  1. Radio & Signals Fundamentals 2.1 – Radio Signals & Waves HPST Technician Course

  2. System of Metric Units Tera T 1012 1,000,000,000,000 Giga G 109 1,000,000,000 Mega M 106 1,000,000 Kilok 103 1,000 Basic Unit 100 1 Milli m 10-3 0.001 Microμ 10-6 0.000001 Nano n 10-9 0.000000001 Pico p 10-12 0.000000000001 HPST Technician Course

  3. Units of Measurements 109 106 103 102 101 100 10-1 10-2 10-3 10-6 10-9 10-12 G M k h da d c m µ n p giga mega kilo hecto deca deci centi milli micro nano pico HPST Technician Course

  4. Pop Quiz – 2.1 (Metric System) • Questions • T4E07-11 HPST Technician Course

  5. T5B01 How many milliamperes is 1.5 amperes? A. 15 milliamperes B. 150 milliamperes C. 1,500 milliamperes D. 15,000 milliamperes HPST Technician Course

  6. T5B02 What is another way to specify a radio signal frequency of 1,500,000 Hertz? A. 1500 kHz B. 1500 MHz C. 15 GHz D. 150 kHz HPST Technician Course

  7. T5B04 How many volts are equal to one microvolt? A. One-one millionth of a volt B. One million volts C. One thousand kilovolts D. One-one thousandth of a volt HPST Technician Course

  8. Radio Signals • Radio equipment either generates or manipulates radio “signals” • Signals are electrical energy used to exchange information • Inside or outside of a radio • Other signals • Static (atmosphere, lightning) • Electrical noise (computers and motors) • Power lines (buzzing & humming) HPST Technician Course

  9. Frequency • Frequency • AC current reverses or “oscillates” X number of times per second • Household current = 60 Cycles per second • RF current = Typically >20,000 CPS • Cycles per second referred to as Hertz, abbreviated Hz • 60 CPS = 60 Hz • 1,000 CPS = 1 KHz • 1,000,000 CPS = 1 MHz • Frequency is referred to as f HPST Technician Course

  10. Audio vs. Radio Frequencies • Audio frequencies are those that we can hear • <20,000 Hz or 20 kHz are in the audio range, therefore are referred to as audio frequencies (AF) • Frequencies above 20 kHz are radio frequencies (RF) HPST Technician Course

  11. Harmonics • Even or odd integer multiple of fundamental frequency • Second harmonic of 3.5 MHz = 3.5 MHz X 2 = 7 MHz • Third harmonic of 7 MHz = 7 MHz X 3 = 21 MHz • Fourth Harmonic of 50 MHz = 50 MHz X 4 = 200 MHz • Used in radio design to shift frequencies and create new signals • Can be bad actors • Spurious emissions can cause interference HPST Technician Course

  12. Harmonics HPST Technician Course

  13. Phase • Phase describes relationship between two signals or components of a signal in time • Measured in degrees • 360 degrees in one complete cycle • Voltage & Current • When voltage & current are aligned in time = in phase • When voltage lags current or vice versa, circuit is out of phase HPST Technician Course

  14. V+ 0V time V- One Cycle Phase 90 Degrees 180 Degrees 0 Degrees 360 Degrees 270 Degrees HPST Technician Course

  15. The Radio Spectrum HPST Technician Course

  16. HPST Technician Course

  17. Wavelength • Distance that a wave travels in one complete cycle • Represented by the Greek letter λ (lambda) • Radio waves travel at the speed of light (300,000,000 mps) (c) • Wavelength (in meters) = c/f in hertz or 300,000,000/f(Hz) • Truncated, this means that λ = 300/f (in MHz) • In practice, 300 / 50 Mhz = 6 meters HPST Technician Course

  18. Wavelength HPST Technician Course

  19. 300 Freq (MHz) Wavelength (λ) Formula To convert from frequency to wavelength: Wavelength (λ) = (In Meters) Wavelength and Frequency are Inversely Proportional. As one goes up, the other must go down. HPST Technician Course

  20. V+ 0V time V- One Wavelength (Distance) One Cycle (Time) The Relationship of Frequency and Wavelength The distance a radio wave travels in one cycle is called wavelength. distance HPST Technician Course

  21. Radio & Signals Fundamentals 2.2 - Modulation

  22. Modulation & Demodulation • A transmitter performs two major functions • Generates radio waves • Adds intelligence to the signal • Process of adding intelligence is modulation • A receiver performs two major functions • Receives radio waves • Extracts the intelligence from the RF signal • Process of extracting the intelligence is demodulation • An RF signal that carries no intelligence is unmodulated 1/18/2011 Hampton Public Service Team 22

  23. Basic Modes • Simplest RF signal is a continuous wave, abbreviated CW • One frequency, transmitter is on all the time, strength never changes • Combination of modulation method and information type is the communication mode • Simplest mode is a continuous wave turned on and off in some pattern, such as Morse code, or radiotelegraphy • Digital or data mode uses binary data to modulate the signal • Analog modes use information understood by humans such as voice 1/18/2011 Hampton Public Service Team 23

  24. Modulation Methods • Modulation can occur in three ways by changing either the: • Amplitude of the signal • Amplitude Modulation (AM) • Frequency of the signal • Frequency Modulation (FM) • Phase of the signal • Phase Modulation (PM) 1/18/2011 Hampton Public Service Team 24

  25. Simple Modulation 1/18/2011 Hampton Public Service Team 25

  26. Amplitude Modulation An unmodulated RF carrier wave A carrier wave AM modulated with a simple audio tone 1/18/2011 Hampton Public Service Team 26

  27. AM and SSB An unmodulated RF carrier requires narrow bandwidth Modulation of the carrier creates sidebands. This requires more bandwidth. Transmitter power is spread across this bandwidth 1/18/2011 Hampton Public Service Team 27

  28. AM and SSB The carrier contains no audio information. The sidebands contain duplicate audio information By filtering out the carrier and one sideband, we save spectrum and concentrate our RF energy into a narrower bandwidth. SSB is therefore more efficient. 1/18/2011 Hampton Public Service Team 28

  29. AM and SSB When AM is not modulated (when you are not talking), the transmitter remains at full power When SSB is not modulated the transmitter output power drops to almost nothing. When either AM or SSB is over-modulated the signal may cause “splatter,” and interfere with other stations. The process of extracting speech or music from an AM or SSB signal is called detection 1/18/2011 Hampton Public Service Team 29

  30. Frequency Modulation • Frequency varies in proportion to the modulating signal • Amount frequency varies when modulated is called deviation • FM transmitters operate at full power at all times, even when you are not talking. • When over-modulated, the signal can be so wide (bandwidth) it may interfere with adjacent channels. This is called over-deviation. • Speaking louder into the microphone may cause over-deviation • Eliminate by moving the microphone away from your mouth or speaking more softly 1/18/2011 Hampton Public Service Team 30

  31. Frequency Modulation • FM signals have one carrier and several sidebands • 5-15 kHz wide • Amplitude doesn’t change, same power all the time • Limiter circuit strips away all amplitude variations, including noise • Compare AM radio to FM Radio • Static • Engine noise • Lightning 1/18/2011 Hampton Public Service Team 31

  32. Frequency Modulation • A: Unmodulated carrier, full power at all times • B. Waveform of modulating signal • C. Modulated carrier with frequency deviation and constant amplitude 1/18/2011 Hampton Public Service Team 32

  33. Phase Modulation • Very similar to frequency modulation • In FM, the frequency of the signal is varied • In phase modulation (PM), the phase of the signal is varied • Both modes received with the same circuitry • Most hams don’t know whether their “FM” transceiver is really FM or PM 1/18/2011 Hampton Public Service Team 33

  34. AM vs. SSB • AM • Sounds really nice • Inexpensive • Simpler equipment • Uses a lot of bandwidth • SSB • More efficient. • Further range based on same output power. • Narrower bandwidth, more room on crowded bands. • All modern HF radios support SSB • Most common voice mode on HF bands 1/18/2011 Hampton Public Service Team 34

  35. SSB & CW • SSB uses less bandwidth than FM • Typically 2-3 kHz vs. 5-15 kHz • Power concentrated into narrow bandwidth • Allows comms over longer ranges and under poor conditions • Below 10 MHz use LSB (except 60 meters) • Above 10 MHz use USB • CW uses even less bandwidth • 150 Hz (Correct table 2-3) • Best mode for weak signal communications 1/18/2011 Hampton Public Service Team 35

  36. Ten Minute Break Be Back On Time!

  37. Radio & Signal Fundamentals 2.3 – Radio Equipment Basics 1/18/2011 HPST Technician Course 37

  38. Basic Station Organization Antenna T-R Switch Transmitter Receiver Power Supply GROUND! Something’s Missing! • Transmitter • Receiver • Antenna • T-R switch • Power Supply 1/18/2011 HPST Technician Course 38

  39. Basic Station Organization Antenna T-R Switch Transmitter Receiver Power Supply • Transmitter (XMTR) • Generates a signal that carries speech, Morse code or data info • Receiver (RCVR) • Recovers the speech, Morse code or data info from a signal • Transceiver (XCVR) • Combines transmitter and receiver into one unit with self contained T-R switch 1/18/2011 HPST Technician Course 39

  40. Transcievers Transmitter and receiver combined in one unit Xmtr and rcvr share circuitry 1/18/2011 HPST Technician Course 40

  41. Antenna & Feed Line • Antenna • Turns energy from the transmitter into radio waves • Captures radio waves, turns them into signals for the receiver • Feed Line • Also called transmission lines • Connects the antenna to the transmitter and receiver 1/18/2011 HPST Technician Course 41

  42. Repeaters Special kind of relay station Receive and transmit at the same time Weak signal is received, amplified and retransmitted Receives and transmits on slightly different frequencies Uses a duplexer instead of a T-R switch Provides relay for weak and mobile stations, extends their coverage 1/18/2011 HPST Technician Course 42

  43. Repeaters 1/18/2011 HPST Technician Course 43

  44. Accessory Radio Equipment • Power Supply • Converts household electrical power to power that can be used by the other station equipment • Microphone • Turns the operator’s voice into electrical signal called “audio” • Speaker • Turns audio signals into sound waves • Headphones • Used in place of speaker when listening to weak signals or in high ambient noise environments 1/18/2011 HPST Technician Course 44

  45. Accessories – Amplifiers • Amplifier • Increases the strength of a signal • Can be internal or external • Preamplifier • Increases the strength of a signal from the antenna before it is sent to the receiver • Power Amplifier (Linear) • Increases the strength of the a signal from the transmitter before it is sent to the antenna 1/18/2011 HPST Technician Course 45

  46. Power Amplifiers Amplifiers increase the power output of the transmitter 1/18/2011 HPST Technician Course 46

  47. Pop Quiz – Section 2.3 1/18/2011 HPST Technician Course 47

  48. T7A10 What device increases the low power output from a hand-held transceiver? A. A voltage divider B. An RF power amplifier C. An impedance network D. A voltage regulator 1/18/2011 HPST Technician Course 48

  49. T4A10 What is the source of a high-pitched whine that varies with engine speed in a mobile transceiver’s receive audio? A. The ignition system B. The alternator C. The electric fuel pump D. Anti-lock braking system controllers 1/18/2011 HPST Technician Course 49

  50. T1F09 What type of amateur station simultaneously retransmits the signal of another amateur station on a different channel or channels? A. Beacon Station B. Earth Station C. Repeater Station D. Message Forwarding Station 1/18/2011 HPST Technician Course 50

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