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Technician License Class Chapter 3 Electricity, Components and Circuits.

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1 Technician License Class Chapter 3 Electricity, Components and Circuits

2 Electricity  Voltage and Current  Current is the flow of electrons through a material.  The magnitude of a current is the number of electrons flowing past a given point in one second  Measured in amperes  1 Amp = 1 coulomb/second  1 coulomb ≈ 6.24 billion billion (6.24 x ) electrons  Abbreviated to ”Amp” or “A”  Use symbol “I” in formulas  Current is measured using an ammeter.

3 Electricity  Voltage and Current  Voltage is the electrical force that causes electrons to flow.  a.k.a. – Electromotive force (EMF), potential.  Measured in volts.  Abbreviated to “V”  Use symbol “E” in formulas  Voltage is measured using a voltmeter.

4 Electricity  Voltage and Current  Voltage has polarity.  Positive voltage attracts electrons.  Negative voltage repels electrons.  Voltage is always referenced between 2 points.  Surface of the earth is often used as a universal reference point.  Called earth ground, ground potential, or ground.

5 T5A01 -- Electrical current is measured in which of the following units? A.Volts B.Watts C.Ohms D.Amperes

6 T5A03 -- What is the name for the flow of electrons in an electric circuit? A.Voltage B.Resistance C.Capacitance D.Current

7 T5A05 -- What is the electrical term for the electromotive force (EMF) that causes electron flow? A.Voltage B.Ampere-hours C.Capacitance D.Inductance

8 T5A11 -- What is the basic unit of electromotive force? A.The volt B.The watt C.The ampere D.The ohm

9 Electricity  Resistance  All materials resist the flow of electrons.  Materials with very little resistance are called conductors.  Materials with a lot of resistance are called insulators.  Resistance is measured in ohms.  Symbol is Greek letter Omega (Ω).  Use “R” in formulas.  Measured with an ohmmeter.

10 T5A07 -- Which of the following is a good electrical conductor? A.Glass B.Wood C.Copper D.Rubber

11 T5A08 -- Which of the following is a good electrical insulator? A.Copper B.Glass C.Aluminum D.Mercury

12 T7D05 -- What instrument is used to measure resistance? A.An oscilloscope B.A spectrum analyzer C.A noise bridge D.An ohmmeter

13 Electricity  Ohm’s Law  First published in 1827 by Georg Ohm in his book “Die galvanische Kette, mathematisch bearbeitet ”  Mathematically describes the relationship between voltage, current, and resistance.  Most basic formula in electricity and electronics.

14 Electricity  Ohm’s Law  E = Electromotive Force  Force causing electrons to flow.  I = Current Intensity  Number of electrons flowing past a point in a given period of time.  R = Resistance  Opposition to flow of electrons. E = I x R I = E/R R = E/I

15 Electricity  Voltage and Current  The flow of water through a hose is a good analogy to understand the characteristics of electricity and how they are related.

16 T5D01 -- What formula is used to calculate current in a circuit? A.Current (I) equals voltage (E) multiplied by resistance (R) B.Current (I) equals voltage (E) divided by resistance (R) C.Current (I) equals voltage (E) added to resistance (R) D.Current (I) equals voltage (E) minus resistance (R)

17 T5D02 -- What formula is used to calculate voltage in a circuit? A.Voltage (E) equals current (I) multiplied by resistance (R) B.Voltage (E) equals current (I) divided by resistance (R) C.Voltage (E) equals current (I) added to resistance (R) D.Voltage (E) equals current (I) minus resistance ®

18 T5D03 -- What formula is used to calculate resistance in a circuit? A.Resistance (R) equals voltage (E) multiplied by current (I) B.Resistance (R) equals voltage (E) divided by current (I) C.Resistance (R) equals voltage (E) added to current (I) D.Resistance (R) equals voltage (E) minus current (I)

19 T5D04 -- What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts? A.3 ohms B.30 ohms C.93 ohms D.270 ohms

20 T5D05 -- What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes? A.18 ohms B ohms C.8 ohms D.13.5 ohms

21 T5D06 -- What is the resistance of a circuit that draws 4 amperes from a 12- volt source? A.3 ohms B.16 ohms C.48 ohms D.8 Ohms

22 T5D07 -- What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms? A.9600 amperes B.200 amperes C amperes D.1.5 amperes

23 T5D08 -- What is the current flowing through a 100-ohm resistor connected across 200 volts? A.20,000 amperes B.0.5 amperes C.2 amperes D.100 amperes

24 T5D09 -- What is the current flowing through a 24-ohm resistor connected across 240 volts? A.24,000 amperes B.0.1 amperes C.10 amperes D.216 amperes

25 T5D10 -- What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it? A.1 volt B.0.25 volts C.2.5 volts D.1.5 volts

26 T5D11 -- What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it? A.1 volt B.10 volts C.11 volts D.9 volts

27 T5D12 -- What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it? A.8 volts B.0.2 volts C.12 volts D.20 volts

28 Electricity  Circuits  A circuit is any path where current can flow.  For current to flow, the circuit must be closed.  Current eventually ends up back where it started.  If only one path, it is a series circuit.  If multiple paths, it is a parallel circuit.

29 Electricity  Circuits  Series circuit

30 Electricity  Circuits  Parallel circuit

31 Electricity  Circuits  Measuring voltage and current  Voltmeters are always placed in parallel with the circuit.  Ammeters are always placed in series with the circuit

32 T7D01 -- Which instrument would you use to measure electric potential or electromotive force? A.An ammeter B.A voltmeter C.A wavemeter D.An ohmmeter

33 T7D02 -- What is the correct way to connect a voltmeter to a circuit? A.In series with the circuit B.In parallel with the circuit C.In quadrature with the circuit D.In phase with the circuit

34 T7D03 -- How is an ammeter usually connected to a circuit? A.In series with the circuit B.In parallel with the circuit C.In quadrature with the circuit D.In phase with the circuit

35 T7D04 -- Which instrument is used to measure electric current? A.An ohmmeter B.A wavemeter C.A voltmeter D.An ammeter

36 Electricity  The Multimeter  The most basic piece of test equipment.  Everybody should have one.  Three (or more) instruments in one:  Voltmeter  Ammeter  Ohmmeter  Measures volts, amperes, and ohms in one package.

37 Electricity  The Multimeter  Digital multimeter (DVM)  Very inexpensive.  Often has extra features in addition to measuring volts, amps, & ohms.

38 Electricity  The Multimeter  Meters can only measure current.  A voltmeter measures voltage by: 1.Placing a known resistance in series with the voltage being measured. 2.Measuring the resulting current. 3.Calculating the voltage using Ohm’s law.  An ohmmeter measures resistance by: 1.Applying a known voltage to the circuit being measured. 2.Measuring the resulting current. 3.Calculating the resistance using Ohm’s law.

39 Electricity  The Multimeter  Measuring resistance.  NEVER attempt to measure resistance with power applied to the circuit.  You WILL damage your multimeter.  NEVER attempt to measure voltage with the resistance setting.  You WILL damage your multimeter.

40 Electricity  The Multimeter  If a resistance reading is initially very low but slowly increases to a higher value, it indicates the presence of a large capacitance in the circuit.

41 T7D06 -- Which of the following might damage a multimeter? A.Measuring a voltage too small for the chosen scale B.Leaving the meter in the milliamps position overnight C.Attempting to measure voltage when using the resistance setting D.Not allowing it to warm up properly

42 T7D07 -- Which of the following measurements are commonly made using a multimeter? A.SWR and RF power B.Signal strength and noise C.Impedance and reactance D.Voltage and resistance

43 T7D10 -- What is probably happening when an ohmmeter, connected across an unpowered circuit, initially indicates a low resistance and then shows increasing resistance with time? A.The ohmmeter is defective B.The circuit contains a large capacitor C.The circuit contains a large inductor D.The circuit is a relaxation oscillator

44 T7D11 -- Which of the following precautions should be taken when measuring circuit resistance with an ohmmeter? A.Ensure that the applied voltages are correct B.Ensure that the circuit is not powered C.Ensure that the circuit is grounded D.Ensure that the circuit is operating at the correct frequency

45 T7D12 -- Which of the following precautions should be taken when measuring high voltages with a voltmeter? A.Ensure that the voltmeter has very low impedance B.Ensure that the voltmeter and leads are rated for use at the voltages to be measured C.Ensure that the circuit is grounded through the voltmeter D.Ensure that the voltmeter is set to the correct frequency

46 Electricity  Power  The rate at which energy is consumed.  Measured in watts  Abbreviated “W”  Use symbol “P” in formulas  Power is measured using a wattmeter.

47 Electricity  Power P EI Watts VoltsAmps P = E x I E = P / I I = P / E P = E 2 /R P = I 2 x R P = Power E = Voltage I = Current

48 Electricity  AC and DC  When current flows in only one direction, it is called direct current (DC).  Batteries are a common source of DC.  Most electronic devices are powered by DC.  When current flows alternatively in one direction then in the opposite direction, it is called alternating current (AC).  Rate at which direction changes is called the frequency.  Your household current is AC.

49 T5A02 -- Electrical power is measured in which of the following units? A.Volts B.Watts C.Ohms D.Amperes

50 T5A04 -- What is the name for a current that flows only in one direction? A.Alternating current B.Direct current C.Normal current D.Smooth current

51 T5A09 -- What is the name for a current that reverses direction on a regular basis? A.Alternating current B.Direct current C.Circular current D.Vertical current

52 T5A10 -- Which term describes the rate at which electrical energy is used? A.Resistance B.Current C.Power D.Voltage

53 T5C08 -- What is the formula used to calculate electrical power in a DC circuit? A.Power (P) equals voltage (E) multiplied by current (I) B.Power (P) equals voltage (E) divided by current (I) C.Power (P) equals voltage (E) minus current (I) D.Power (P) equals voltage (E) plus current (I)

54 T5C09 -- How much power is being used in a circuit when the applied voltage is 13.8 volts DC and the current is 10 amperes? A.138 watts B.0.7 watts C.23.8 watts D.3.8 watts

55 T5C10 -- How much power is being used in a circuit when the applied voltage is 12 volts DC and the current is 2.5 amperes? A.4.8 watts B.30 watts C.14.5 watts D watts

56 T5C11 -- How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and the load is 120 watts? A.0.1 amperes B.10 amperes C.12 amperes D.132 amperes

57 Components  Basic Components  There are 3 basic types of components:  Resistor  Unit of measurement of resistance is the ohm (Ω).  Capacitor  Unit of measurement of capacitance is the farad (F).  Inductor  Unit of measurement of inductance is the henry (H).

58 Components  Basic Components  Resistors  The function of the resistor is to oppose the flow of electric current.  Dissipates energy as heat.  Potentiometer.  Volume control.

59 Components  Basic Components  Resistors.  A fixed amount of a partially conductive material.  Ratings.  Resistance.  Ohms (Ω), kilohms (kΩ), megohms (MΩ)  Values from 10 MΩ.  Maximum power in watts (W).  Values from a fraction of a watt to a couple to >100 W.

60 Components  Basic Components  Capacitors.  The function of the capacitor is to temporarily store electrical energy.  Stores energy in an electric field.  Like a very temporary storage battery.

61 Components  Basic Components  Capacitors.  Two conductive surfaces separated by an insulator.  Ratings.  Capacitance in picofarads (pF), microfarads (μF), or farads (F).  Values from 1 pF to 1 F.  Maximum voltage in volts (V), or kilovolts (kV).  Values from a few volts to several kilovolts.

62 Components  Basic Components  Inductors.  The function of the inductor is to temporarily store electrical energy.  Basically a coil of wire.  Stores energy in a magnetic field.

63 Components  Basic Components  Inductors.  A coil of wire wound around a non-magnetic form or a magnetic core.  Ratings.  Inductance in microhenries (μH), millihenries (mH), or henries (H).  A few microhenries to several henries.  Maximum current in milliamperes (mA) or amperes (A).  A few milliamperes to several amperes.

64 Components  Basic Components  Transformers.  Two or more inductors arranged so that they share their stored magnetic energy.  Used to change AC voltage levels.  e.g. - Change 120 V AC household voltage to a lower value for use in electronic equipment.

65 Components  Color Code.  Component values often marked on component by colored stripes or dots.  Very common with resistors.  Less common with capacitors and inductors.  Axial-lead cases.

66 Components  Color Code.

67 Components  Color Code.  Bad Boys Rape Our Young Girls But Violet Gives Willingly.  Bad Boys Rape Our Young Girls Behind Victory Garden Walls.  Bad Beer Rots Out Your Guts But Veggies Go Well.  Get Some Now (tolerance)

68 T5C01 -- What is the ability to store energy in an electric field called? A.Inductance B.Resistance C.Tolerance D.Capacitance

69 T5C02 -- What is the basic unit of capacitance? A.The farad B.The ohm C.The volt D.The henry

70 T5C03 -- What is the ability to store energy in a magnetic field called? A.Admittance B.Capacitance C.Resistance D.Inductance

71 T5C04 -- What is the basic unit of inductance? A.The coulomb B.The farad C.The henry D.The ohm

72 T6A01 -- What electrical component is used to oppose the flow of current in a DC circuit? A.Inductor B.Resistor C.Voltmeter D.Transformer

73 T6A02 -- What type of component is often used as an adjustable volume control? A.Fixed resistor B.Power resistor C.Potentiometer D.Transformer

74 T6A03 -- What electrical parameter is controlled by a potentiometer? A.Inductance B.Resistance C.Capacitance D.Field strength

75 T6A04 -- What electrical component stores energy in an electric field? A.Resistor B.Capacitor C.Inductor D.Diode

76 T6A05 -- What type of electrical component consists of two or more conductive surfaces separated by an insulator? A.Resistor B.Potentiometer C.Oscillator D.Capacitor

77 T6A06 -- What type of electrical component stores energy in a magnetic field? A.Resistor B.Capacitor C.Inductor D.Diode

78 T6A07 -- What electrical component is usually composed of a coil of wire? A.Switch B.Capacitor C.Diode D.Inductor

79 T6D06 -- What component is commonly used to change 120V AC house current to a lower AC voltage for other uses? A.Variable capacitor B.Transformer C.Transistor D.Diode

80 Components  Reactance and Impedance.  In circuits containing only resistors, voltage & current are always “in phase”.  Current flow changes at the same time and in the same direction as the voltage change.  A special kind of resistance to the flow of AC is called reactance (X).  Reactance also measured in Ohms (Ω).

81 Components  Reactance and Impedance.  In circuits containing capacitors or inductors, voltage & current are “out of phase”.  Current flow changes before the voltage changes in a capacitor.  Current “leads” voltage.  Current flow changes after the voltage changes in an inductor.  Current “lags” voltage.

82 Components  Reactance and Impedance.  Opposition to AC current flow in capacitors or inductors is called reactance (X).  Reactance (R) is measured in Ohms (Ω).  Capacitive reactance (X C ) is measured in Ohms (Ω).  Inductive reactance (X L ) is measured in Ohms (Ω).  Combination of resistance and reactance is called impedance (Z).  Impedance (Z) is measured in Ohms (Ω).

83 Components  Resonance. Because current leads voltage in a capacitor & lags voltage in an inductor, a combination exists where the lead time & lag time cancel, resulting in the current & voltage being in phase.

84 Components  Resonance. This condition is called resonance. Resonant circuit. a.k.a. - Tuned circuit. Acts as filter. Used to adjust frequency of receiver or transmitter. The capacitive reactance (X C ) and inductive reactance (X L ) in a resonant circuit are equal. Impedance (Z) of a resonant circuit is purely resistive. Reactance = 0Ω.

85 T5C12 -- What is meant by the term impedance? A.It is a measure of the opposition to AC current flow in a circuit B.It is the inverse of resistance C.It is a measure of the Q or Quality Factor of a component D.It is a measure of the power handling capability of a component

86 T5C13 -- What are the units of impedance? A.Volts B.Amperes C.Coulombs D.Ohms

87 T6D08 -- Which of the following is used together with an inductor to make a tuned circuit? A.Resistor B.Zener diode C.Potentiometer D.Capacitor

88 T6D11 -- What is a simple resonant or tuned circuit? A.An inductor and a capacitor connected in series or parallel to form a filter B.A type of voltage regulator C.A resistor circuit used for reducing standing wave ratio D.A circuit designed to provide high fidelity audio

89 Break

90 Components  Diodes, Transistors, and Integrated Circuits.  Resistors, capacitors, and inductors are linear devices.  Response is ALWAYS directly proportional to the stimulus.  Diodes and transistors are non-linear devices.  Response is not always directly proportional to the stimulus.

91 Components  Diodes, Transistors, and Integrated Circuits.  The function of the diode is to allow the flow of current in only one direction.  Connections named anode & cathode.  Cathode normally identified with a stripe.  An analogy is a check valve in a water pipe.

92 Components  Diodes, Transistors, and Integrated Circuits. One use of a diode is as a rectifier in a power supply circuit to convert an AC voltage into a varying DC voltage.

93 Components  Diodes, Transistors, and Integrated Circuits. Light-Emitting Diode (LED). Emits light when forward-biased.

94 Components  Diodes, Transistors, and Integrated Circuits. The function of the transistor is to variably control the flow of current. Much like an electronically controlled valve. An analogy, the faucet in your sink.

95 Components  Diodes, Transistors, and Integrated Circuits. Transistors can be used to amplify a signal. The amount of amplification is called “gain”.  Transistors can be used to electronically turn the flow of current on or off like a switch.

96 Components  Diodes, Transistors, and Integrated Circuits. Bipolar Transistors. Connections named Emitter, Base, & Collector. Small change in base current results in large change in emitter current. Low input & output impedances.

97 Components  Diodes, Transistors, and Integrated Circuits.

98 Components  Diodes, Transistors, and Integrated Circuits. Field-Effect Transistors (FET). Connections named Source, Gate, & Drain. Small change in gate voltage results in large change in drain current. High input impedance & low output impedance.

99 Components  Diodes, Transistors, and Integrated Circuits. An integrated circuit is a collection of components contained in one device that accomplishes a specific task. Acts like a “black-box”

100 T6B01 -- What class of electronic components is capable of using a voltage or current signal to control current flow? A.Capacitors B.Inductors C.Resistors D.Transistors

101 T6B02 -- What electronic component allows current to flow in only one direction? A.Resistor B.Fuse C.Diode D.Driven Element

102 T6B03 -- Which of these components can be used as an electronic switch or amplifier? A.Oscillator B.Potentiometer C.Transistor D.Voltmeter

103 T6B04 -- Which of the following components can be made of three layers of semiconductor material? A.Alternator B.Transistor C.Triode D.Pentagrid converter

104 T6B05 -- Which of the following electronic components can amplify signals? A.Transistor B.Variable resistor C.Electrolytic capacitor D.Multi-cell battery

105 T6B06 -- How is the cathode lead of a semiconductor diode usually identified? A.With the word cathode B.With a stripe C.With the letter C D.All of these choices are correct

106 T6B07 -- What does the abbreviation LED stand for? A.Low Emission Diode B.Light Emitting Diode C.Liquid Emission Detector D.Long Echo Delay

107 T6B08 -- What does the abbreviation FET stand for? A.Field Effect Transistor B.Fast Electron Transistor C.Free Electron Transition D.Field Emission Thickness

108 T6B09 -- What are the names of the two electrodes of a diode? A.Plus and minus B.Source and drain C.Anode and cathode D.Gate and base

109 T6B10 -- What are the three electrodes of a PNP or NPN transistor? A.Emitter, base, and collector B.Source, gate, and drain C.Cathode, grid, and plate D.Cathode, drift cavity, and collector

110 T6B11 -- What at are the three electrodes of a field effect transistor? A.Emitter, base, and collector B.Source, gate, and drain C.Cathode, grid, and plate D.Cathode, gate, and anode

111 T6B12 -- What is the term that describes a transistor's ability to amplify a signal? A.Gain B.Forward resistance C.Forward voltage drop D.On resistance

112 T6D01 -- Which of the following devices or circuits changes an alternating current into a varying direct current signal? A.Transformer B.Rectifier C.Amplifier D.Reflector

113 T6D07 -- Which of the following is commonly used as a visual indicator? A.LED B.FET C.Zener diode D.Bipolar transistor

114 T6D09 -- What is the name of a device that combines several semiconductors and other components into one package? A.Transducer B.Multi-pole relay C.Integrated circuit D.Transformer

115 T6D10 -- What is the function of component 2 in Figure T1? A.Give off light when current flows through it B.Supply electrical energy C.Control the flow of current D.Convert electrical energy into radio waves

116 Components  Protective Components. Fuses and circuit breakers are designed to interrupt the flow of current if the current becomes too large.

117 Components  Protective Components. Fuses blow. One-time protection.

118 Components  Protective Components. Circuit breakers trip. Can be reset & reused.

119 Components  Circuit Gatekeepers. Switches The function of the switch is to turn the flow of current on or off or to redirect it.

120 Components  Circuit Gatekeepers. Relays. An electrically-controlled switch. A set of switch contacts connected to an electromagnet.

121 Components  Circuit Gatekeepers. Indicators and displays. An indicator displays on/off status. A meter shows a value on a numeric scale. A display consists of several indicators & meters.

122 T6A08 -- What electrical component is used to connect or disconnect electrical circuits? A.Magnetron B.Switch C.Thermistor D.All of these choices are correct

123 T6A09 -- What electrical component is used to protect other circuit components from current overloads? A.Fuse B.Capacitor C.Inductor D.All of these choices are correct

124 T6D02 -- What best describes a relay? A.A switch controlled by an electromagnet B.A current controlled amplifier C.An optical sensor D.A pass transistor

125 T6D03 -- What type of switch is represented by component 3 in figure T2? A.Single-pole single-throw B.Single-pole double-throw C.Double-pole single-throw D.Double-pole double-throw

126 T6D04 -- Which of the following can be used to display signal strength on a numeric scale? A.Potentiometer B.Transistor C.Meter D.Relay

127 T0A04 -- What is the purpose of a fuse in an electrical circuit? A.To prevent power supply ripple from damaging a circuit B.To interrupt power in case of overload C.To limit current to prevent shocks D.All of these choices are correct

128 T0A05 -- Why is it unwise to install a 20-ampere fuse in the place of a 5- ampere fuse? A.The larger fuse would be likely to blow because it is rated for higher current B.The power supply ripple would greatly increase C.Excessive current could cause a fire D.All of these choices are correct

129 Components  Schematics and Component Symbols  Schematic diagrams  Use a set of standard symbols for each component in a circuit.  Represent the way components are interconnected.  Do NOT represent the physical layout of the components.  Do NOT represent the length of the conductors used for the interconnections.

130 Components  Schematics and Component Symbols  Schematic diagrams

131 Components  Schematics and Component Symbols  Schematic diagrams

132 T6C01 -- What is the name for standardized representations of components in an electrical wiring diagram? A.Electrical depictions B.Grey sketch C.Schematic symbols D.Component callouts

133 T6C02 -- What is component 1 in figure T1? A.Resistor B.Transistor C.Battery D.Connector

134 T6C03 -- What is component 2 in figure T1? A.Resistor B.Transistor C.Indicator lamp D.Connector

135 T6C04 -- What is component 3 in figure T1? A.Resistor B.Transistor C.Lamp D.Ground symbol

136 T6C05 -- What is component 4 in figure T1? A.Resistor B.Transistor C.Battery D.Ground symbol

137 T6C06 -- What is component 6 in figure T2? A.Resistor B.Capacitor C.Regulator IC D.Transistor

138 T6C07 -- What is component 8 in figure T2? A.Resistor B.Inductor C.Regulator IC D.Light emitting diode

139 T6C What is component 9 in figure T2? A.Variable capacitor B.Variable inductor C.Variable resistor D.Variable transformer

140 T6C09 -- What is component 4 in figure T2? A.Variable inductor B.Double-pole switch C.Potentiometer D.Transformer

141 T6C10 -- What is component 3 in figure T3? A.Connector B.Meter C.Variable capacitor D.Variable inductor

142 T6C11 -- What is component 4 in figure T3? A.Antenna B.Transmitter C.Dummy load D.Ground

143 T6C12 -- What do the symbols on an electrical circuit schematic diagram represent? A.Electrical components B.Logic states C.Digital codes D.Traffic nodes

144 T6C13 -- Which of the following is accurately represented in electrical circuit schematic diagrams? A.Wire lengths B.Physical appearance of components C.The way components are interconnected D.All of these choices are correct

145 Types of Radios and Radio Circuits  Basic 2-Way Radio Station.

146 Types of Radios and Radio Circuits  Transmit-Receive Switches.  Switches antenna between antenna and receiver.  Transceivers include the T/R switch as an internal circuit.  External T/R switch required if separate transmitter & receiver are used.

147 Types of Radios and Radio Circuits  Oscillators and Amplifiers. Oscillators produce a steady AC voltage on a single frequency. Used in both receivers & transmitters to determine operating frequency. Crystal-controlled oscillator. Variable-frequency oscillator (VFO).

148 Types of Radios and Radio Circuits  Oscillators and Amplifiers. Amplifiers increase the strength of a signal. Increase voltage, current, or power. Amount of increase is called “gain”. Numeric value – For example, a gain of 10 means the output signal is 10 times bigger than input signal. dB – For example, a power gain of 3 dB means the output signal has twice the power than the input signal.

149 Types of Radios and Radio Circuits  Filters.  Allow wanted signals to pass through.  Prevent unwanted signals from passing through.  Filters constructed using all passive components (resistors, capacitors, & inductors) are called “passive” filters.  Fitters that include an amplifier are called “active” filters.

150 Types of Radios and Radio Circuits  Filters.  There are 4 basic classifications of filters:  Low-pass filter.  High-pass filter.  Band-pass filter.  Band reject filter.  a.k.a. – notch filter.

151 Types of Radios and Radio Circuits  Modulators.  The process of combining information (voice, data, etc.) signals with an RF signal (carrier) is called “modulation”. Can be as simple as an on-off switch. Telegraph key. Can be very complex. A “demodulator” extracts the original information signal from the carrier.

152 Types of Radios and Radio Circuits  Mixers. Mixers combine 2 different frequency signals together to produce 4 output frequencies. f 1 x f 2  f 1, f 2, f 1 -f 2, & f 1 +f 2. Usually only one output frequency wanted, so filters remove other 3 frequencies. Used in both transmitters & receivers. Used to shift a signal or group of signals to another frequency.

153 T7A03 -- Which of the following is used to convert a radio signal from one frequency to another? A.Phase splitter B.Mixer C.Inverter D.Amplifier

154 T7A05 -- What is the name of a circuit that generates a signal of a desired frequency? A.Reactance modulator B.Product detector C.Low-pass filter D.Oscillator

155 T7A08 -- Which of the following describes combining speech with an RF carrier signal? A.Impedance matching B.Oscillation C.Modulation D.Low-pass filtering

156 Types of Radios and Radio Circuits  Receivers.  A receiver gets the desired RF signal from the antenna and presents the original information to the user.  Many different types of receivers.  Direct-conversion.  If you count cell phones, most common type.  Superheterodyne.  Most common type used by amateur radio operators.

157 Types of Radios and Radio Circuits  Receivers.  Direct-conversion receiver. Local oscillator at (or near) frequency of signal to be received. Advantage: Very easy to filter at audio frequency. Advantage: No image responses. Disadvantage: High stability local oscillator required. Most software-defined radios (including cell phones) use direct-conversion receivers.

158 Types of Radios and Radio Circuits  Receivers.  Heterodyne receiver. RF & local oscillator fed into mixer to move signal to a lower intermediate frequency (IF) for filtering & demodulation. Advantage: Easier to filter at lower frequency. Disadvantage: Image responses. Superheterodyne. f LO > f RF.

159 Types of Radios and Radio Circuits  Receivers.  Heterodyne receiver.

160 Types of Radios and Radio Circuits  Receivers.  Sensitivity is a measure of how weak a signal can be received.  Sometimes a pre-amplifier (pre-amp) is installed between the antenna and the mixer to improve sensitivity.

161 Types of Radios and Radio Circuits  Receivers.  Selectivity is a measure of how well a receiver can differentiate between signals.  Filters are used to provide selectivity.

162 Types of Radios and Radio Circuits  Transverters.  The heterodyne method of shifting a frequency or range of frequencies can be used to shift a transceiver to a whole different band.  Allows HF transceiver to be used on VHF, UHF, & microwave frequencies.  Many amateur radio satellites are transverters.

163 T7A01 -- Which term describes the ability of a receiver to detect the presence of a signal? A.Linearity B.Sensitivity C.Selectivity D.Total Harmonic Distortion

164 T7A04 -- Which term describes the ability of a receiver to discriminate between multiple signals? A.Discrimination ratio B.Sensitivity C.Selectivity D.Harmonic Distortion

165 T7A06 -- What device takes the output of a low-powered 28 MHz SSB exciter and produces a 222 MHz output signal? A.High-pass filter B.Low-pass filter C.Transverter D.D. Phase converter

166 T7A11 -- Where is an RF preamplifier installed? A.Between the antenna and receiver B.At the output of the transmitter's power amplifier C.Between a transmitter and antenna tuner D.At the receiver's audio output

167 Questions?

168 Next Week Chapter 4 Propagation, Antennas, and Feed Lines


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