Presentation on theme: "Technician License Class"— Presentation transcript:
1Technician License Class Chapter 3Electricity, Components and Circuits
2Electricity 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 secondMeasured in amperes1 Amp = 1 coulomb/second1 coulomb ≈ 6.24 billion billion (6.24 x 1018) electronsAbbreviated to ”Amp” or “A”Use symbol “I” in formulasCurrent is measured using an ammeter.
3Electricity 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 formulasVoltage is measured using a voltmeter.
4Electricity 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.
5Volts Watts Ohms Amperes T5A01 -- Electrical current is measured in which of the following units?VoltsWattsOhmsAmperes
6Voltage Resistance Capacitance Current T5A03 -- What is the name for the flow of electrons in an electric circuit?VoltageResistanceCapacitanceCurrent
7Voltage Ampere-hours Capacitance Inductance T5A05 -- What is the electrical term for the electromotive force (EMF) that causes electron flow?VoltageAmpere-hoursCapacitanceInductance
8T5A11 -- What is the basic unit of electromotive force? The voltThe wattThe ampereThe ohm
9Electricity 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.
10T5A07 -- Which of the following is a good electrical conductor? GlassWoodCopperRubber
11T5A08 -- Which of the following is a good electrical insulator? CopperGlassAluminumMercury
12T7D05 -- What instrument is used to measure resistance? An oscilloscopeA spectrum analyzerA noise bridgeAn ohmmeter
13ElectricityOhm’s LawFirst 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.
14Electricity Ohm’s Law R = Resistance E = I x R I = E/R R = E/I E = Electromotive ForceForce causing electrons to flow.I = Current IntensityNumber of electrons flowing past a point in a given period of time.R = ResistanceOpposition to flow of electrons.E = I x RI = E/RR = E/I
15Electricity 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.
16T5D01 -- What formula is used to calculate current in a circuit? Current (I) equals voltage (E) multiplied by resistance (R)Current (I) equals voltage (E) divided by resistance (R)Current (I) equals voltage (E) added to resistance (R)Current (I) equals voltage (E) minus resistance (R)
17T5D02 -- What formula is used to calculate voltage in a circuit? Voltage (E) equals current (I) multiplied by resistance (R)Voltage (E) equals current (I) divided by resistance (R)Voltage (E) equals current (I) added to resistance (R)Voltage (E) equals current (I) minus resistance ®
18T5D03 -- What formula is used to calculate resistance in a circuit? Resistance (R) equals voltage (E) multiplied by current (I)Resistance (R) equals voltage (E) divided by current (I)Resistance (R) equals voltage (E) added to current (I)Resistance (R) equals voltage (E) minus current (I)
19T5D04 -- What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts?3 ohms30 ohms93 ohms270 ohms
20T5D05 -- What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes?18 ohms0.125 ohms8 ohms13.5 ohms
21T5D06 -- What is the resistance of a circuit that draws 4 amperes from a 12-volt source? 3 ohms16 ohms48 ohms8 Ohms
229600 amperes 200 amperes 0.667 amperes 1.5 amperes T5D07 -- What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?9600 amperes200 amperes0.667 amperes1.5 amperes
2320,000 amperes 0.5 amperes 2 amperes 100 amperes T5D08 -- What is the current flowing through a 100-ohm resistor connected across 200 volts?20,000 amperes0.5 amperes2 amperes100 amperes
2424,000 amperes 0.1 amperes 10 amperes 216 amperes T5D09 -- What is the current flowing through a 24-ohm resistor connected across 240 volts?24,000 amperes0.1 amperes10 amperes216 amperes
25T5D10 -- What is the voltage across a 2-ohm resistor if a current of 0 T5D10 -- What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it?1 volt0.25 volts2.5 volts1.5 volts
26T5D11 -- What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it? 10 volts11 volts9 volts
278 volts 0.2 volts 12 volts 20 volts T5D12 -- What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it?8 volts0.2 volts12 volts20 volts
28Electricity 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.
31Electricity Circuits Measuring voltage and current Voltmeters are always placed in parallel with the circuit.Ammeters are always placed in series with the circuit
32An ammeter A voltmeter A wavemeter An ohmmeter T7D01 -- Which instrument would you use to measure electric potential or electromotive force?An ammeterA voltmeterA wavemeterAn ohmmeter
33T7D02 -- What is the correct way to connect a voltmeter to a circuit? In series with the circuitIn parallel with the circuitIn quadrature with the circuitIn phase with the circuit
34T7D03 -- How is an ammeter usually connected to a circuit? In series with the circuitIn parallel with the circuitIn quadrature with the circuitIn phase with the circuit
35T7D04 -- Which instrument is used to measure electric current? An ohmmeterA wavemeterA voltmeterAn ammeter
36Electricity The Multimeter The most basic piece of test equipment. Everybody should have one.Three (or more) instruments in one:VoltmeterAmmeterOhmmeterMeasures volts, amperes, and ohms in one package.
37Electricity The Multimeter Digital multimeter (DVM) Very inexpensive. Often has extra features in addition to measuring volts, amps, & ohms.
38Electricity The Multimeter Meters can only measure current. A voltmeter measures voltage by:Placing a known resistance in series with the voltage being measured.Measuring the resulting current.Calculating the voltage using Ohm’s law.An ohmmeter measures resistance by:Applying a known voltage to the circuit being measured.Calculating the resistance using Ohm’s law.
39Electricity 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.
40Electricity 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.
41T7D06 -- Which of the following might damage a multimeter? Measuring a voltage too small for the chosen scaleLeaving the meter in the milliamps position overnightAttempting to measure voltage when using the resistance settingNot allowing it to warm up properly
42Signal strength and noise Impedance and reactance T7D07 -- Which of the following measurements are commonly made using a multimeter?SWR and RF powerSignal strength and noiseImpedance and reactanceVoltage and resistance
43The ohmmeter is defective The circuit contains a large capacitor 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?The ohmmeter is defectiveThe circuit contains a large capacitorThe circuit contains a large inductorThe circuit is a relaxation oscillator
44Ensure that the applied voltages are correct T7D11 -- Which of the following precautions should be taken when measuring circuit resistance with an ohmmeter?Ensure that the applied voltages are correctEnsure that the circuit is not poweredEnsure that the circuit is groundedEnsure that the circuit is operating at the correct frequency
45Ensure that the voltmeter has very low impedance T7D12 -- Which of the following precautions should be taken when measuring high voltages with a voltmeter?Ensure that the voltmeter has very low impedanceEnsure that the voltmeter and leads are rated for use at the voltages to be measuredEnsure that the circuit is grounded through the voltmeterEnsure that the voltmeter is set to the correct frequency
46Electricity Power The rate at which energy is consumed. Measured in wattsAbbreviated “W”Use symbol “P” in formulasPower is measured using a wattmeter.
47Electricity P E I P = E x I E = P / I I = P / E P = E2/R P = I2 x R PowerP = E x IE = P / II = P / EP = E2/RP = I2 x RPWattsEIVoltsAmpsP = PowerE = VoltageI = Current
48ElectricityAC and DCWhen 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.
49T5A02 -- Electrical power is measured in which of the following units? VoltsWattsOhmsAmperes
50Alternating current Direct current Normal current Smooth current T5A04 -- What is the name for a current that flows only in one direction?Alternating currentDirect currentNormal currentSmooth current
51Alternating current Direct current Circular current Vertical current T5A09 -- What is the name for a current that reverses direction on a regular basis?Alternating currentDirect currentCircular currentVertical current
52Resistance Current Power Voltage T5A10 -- Which term describes the rate at which electrical energy is used?ResistanceCurrentPowerVoltage
53Power (P) equals voltage (E) multiplied by current (I) T5C08 -- What is the formula used to calculate electrical power in a DC circuit?Power (P) equals voltage (E) multiplied by current (I)Power (P) equals voltage (E) divided by current (I)Power (P) equals voltage (E) minus current (I)Power (P) equals voltage (E) plus current (I)
54138 watts 0.7 watts 23.8 watts 3.8 watts 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?138 watts0.7 watts23.8 watts3.8 watts
554.8 watts 30 watts 14.5 watts 0.208 watts 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?4.8 watts30 watts14.5 watts0.208 watts
560.1 amperes 10 amperes 12 amperes 132 amperes T5C11 -- How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and the load is 120 watts?0.1 amperes10 amperes12 amperes132 amperes
57Components Basic Components There are 3 basic types of components: ResistorUnit of measurement of resistance is the ohm (Ω).CapacitorUnit of measurement of capacitance is the farad (F).InductorUnit of measurement of inductance is the henry (H).
58Components Basic Components Resistors The function of the resistor is to oppose the flow of electric current.Dissipates energy as heat.Potentiometer.Volume control.
59Components Basic Components Resistors. A fixed amount of a partially conductive material.Ratings.Resistance.Ohms (Ω), kilohms (kΩ), megohms (MΩ)Values from <1 Ω to >10 MΩ.Maximum power in watts (W).Values from a fraction of a watt to a couple to >100 W.
60Components 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.
61Components 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.
62Components 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.
63Components 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.
64Components 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 VAC household voltage to a lower value for use in electronic equipment.
65ComponentsColor 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.
67ComponentsColor 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)
68Inductance Resistance Tolerance Capacitance T5C01 -- What is the ability to store energy in an electric field called?InductanceResistanceToleranceCapacitance
69T5C02 -- What is the basic unit of capacitance? The faradThe ohmThe voltThe henry
70Admittance Capacitance Resistance Inductance T5C03 -- What is the ability to store energy in a magnetic field called?AdmittanceCapacitanceResistanceInductance
71T5C04 -- What is the basic unit of inductance? The coulombThe faradThe henryThe ohm
72Inductor Resistor Voltmeter Transformer T6A01 -- What electrical component is used to oppose the flow of current in a DC circuit?InductorResistorVoltmeterTransformer
73Fixed resistor Power resistor Potentiometer Transformer T6A02 -- What type of component is often used as an adjustable volume control?Fixed resistorPower resistorPotentiometerTransformer
74T6A03 -- What electrical parameter is controlled by a potentiometer? InductanceResistanceCapacitanceField strength
75T6A04 -- What electrical component stores energy in an electric field? ResistorCapacitorInductorDiode
76Resistor Potentiometer Oscillator Capacitor T6A05 -- What type of electrical component consists of two or more conductive surfaces separated by an insulator?ResistorPotentiometerOscillatorCapacitor
77Resistor Capacitor Inductor Diode T6A06 -- What type of electrical component stores energy in a magnetic field?ResistorCapacitorInductorDiode
78Switch Capacitor Diode Inductor T6A07 -- What electrical component is usually composed of a coil of wire?SwitchCapacitorDiodeInductor
79Variable capacitor Transformer Transistor Diode T6D06 -- What component is commonly used to change 120V AC house current to a lower AC voltage for other uses?Variable capacitorTransformerTransistorDiode
80Components 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).
81Components 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.
82Components 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 (XC) is measured in Ohms (Ω).Inductive reactance (XL) is measured in Ohms (Ω).Combination of resistance and reactance is called impedance (Z).Impedance (Z) is measured in Ohms (Ω).
83ComponentsResonance.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.
84Components 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 (XC) and inductive reactance (XL) in a resonant circuit are equal.Impedance (Z) of a resonant circuit is purely resistive.Reactance = 0Ω.
85T5C12 -- What is meant by the term impedance? It is a measure of the opposition to AC current flow in a circuitIt is the inverse of resistanceIt is a measure of the Q or Quality Factor of a componentIt is a measure of the power handling capability of a component
86T5C13 -- What are the units of impedance? VoltsAmperesCoulombsOhms
87Resistor Zener diode Potentiometer Capacitor T6D08 -- Which of the following is used together with an inductor to make a tuned circuit?ResistorZener diodePotentiometerCapacitor
88T6D11 -- What is a simple resonant or tuned circuit? An inductor and a capacitor connected in series or parallel to form a filterA type of voltage regulatorA resistor circuit used for reducing standing wave ratioA circuit designed to provide high fidelity audio
90Components 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.
91Components 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.
92Components 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.
93Components Diodes, Transistors, and Integrated Circuits. Light-Emitting Diode (LED).Emits light when forward-biased.
94Components 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.
95Components 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.
96Components 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.
97ComponentsDiodes, Transistors, and Integrated Circuits.
98Components 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.
99Components 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”
100Capacitors Inductors Resistors Transistors T6B01 -- What class of electronic components is capable of using a voltage or current signal to control current flow?CapacitorsInductorsResistorsTransistors
101Resistor Fuse Diode Driven Element T6B02 -- What electronic component allows current to flow in only one direction?ResistorFuseDiodeDriven Element
102Oscillator Potentiometer Transistor Voltmeter T6B03 -- Which of these components can be used as an electronic switch or amplifier?OscillatorPotentiometerTransistorVoltmeter
103Alternator Transistor Triode Pentagrid converter T6B04 -- Which of the following components can be made of three layers of semiconductor material?AlternatorTransistorTriodePentagrid converter
104Electrolytic capacitor Multi-cell battery T6B05 -- Which of the following electronic components can amplify signals?TransistorVariable resistorElectrolytic capacitorMulti-cell battery
105All of these choices are correct T6B06 -- How is the cathode lead of a semiconductor diode usually identified?With the word cathodeWith a stripeWith the letter CAll of these choices are correct
106T6B07 -- What does the abbreviation LED stand for? Low Emission DiodeLight Emitting DiodeLiquid Emission DetectorLong Echo Delay
107T6B08 -- What does the abbreviation FET stand for? Field Effect TransistorFast Electron TransistorFree Electron TransitionField Emission Thickness
108T6B09 -- What are the names of the two electrodes of a diode? Plus and minusSource and drainAnode and cathodeGate and base
109T6B10 -- What are the three electrodes of a PNP or NPN transistor? Emitter, base, and collectorSource, gate, and drainCathode, grid, and plateCathode, drift cavity, and collector
110Emitter, base, and collector Source, gate, and drain T6B11 -- What at are the three electrodes of a field effect transistor?Emitter, base, and collectorSource, gate, and drainCathode, grid, and plateCathode, gate, and anode
111Gain Forward resistance Forward voltage drop On resistance T6B12 -- What is the term that describes a transistor's ability to amplify a signal?GainForward resistanceForward voltage dropOn resistance
112Transformer Rectifier Amplifier Reflector T6D01 -- Which of the following devices or circuits changes an alternating current into a varying direct current signal?TransformerRectifierAmplifierReflector
113LED FET Zener diode Bipolar transistor T6D07 -- Which of the following is commonly used as a visual indicator?LEDFETZener diodeBipolar transistor
114Transducer Multi-pole relay Integrated circuit Transformer T6D09 -- What is the name of a device that combines several semiconductors and other components into one package?TransducerMulti-pole relayIntegrated circuitTransformer
115T6D10 -- What is the function of component 2 in Figure T1? Give off light when current flows through itSupply electrical energyControl the flow of currentConvert electrical energy into radio waves
116Components Protective Components. Fuses and circuit breakers are designed to interrupt the flow of current if the current becomes too large.
118Components Protective Components. Circuit breakers trip. Can be reset & reused.
119Components Circuit Gatekeepers. Switches The function of the switch is to turn the flow of current on or off or to redirect it.
120Components Circuit Gatekeepers. Relays. An electrically-controlled switch.A set of switch contacts connected to an electromagnet.
121Components 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.
122All of these choices are correct T6A08 -- What electrical component is used to connect or disconnect electrical circuits?MagnetronSwitchThermistorAll of these choices are correct
123All of these choices are correct T6A09 -- What electrical component is used to protect other circuit components from current overloads?FuseCapacitorInductorAll of these choices are correct
124T6D02 -- What best describes a relay? A switch controlled by an electromagnetA current controlled amplifierAn optical sensorA pass transistor
125Single-pole single-throw Single-pole double-throw T6D03 -- What type of switch is represented by component 3 in figure T2?Single-pole single-throwSingle-pole double-throwDouble-pole single-throwDouble-pole double-throw
126Potentiometer Transistor Meter Relay T6D04 -- Which of the following can be used to display signal strength on a numeric scale?PotentiometerTransistorMeterRelay
127T0A04 -- What is the purpose of a fuse in an electrical circuit? To prevent power supply ripple from damaging a circuitTo interrupt power in case of overloadTo limit current to prevent shocksAll of these choices are correct
128The power supply ripple would greatly increase T0A05 -- Why is it unwise to install a 20-ampere fuse in the place of a 5-ampere fuse?The larger fuse would be likely to blow because it is rated for higher currentThe power supply ripple would greatly increaseExcessive current could cause a fireAll of these choices are correct
129Components 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.
130ComponentsSchematics and Component SymbolsSchematic diagrams
131ComponentsSchematics and Component SymbolsSchematic diagrams
132Electrical depictions Grey sketch Schematic symbols Component callouts T6C01 -- What is the name for standardized representations of components in an electrical wiring diagram?Electrical depictionsGrey sketchSchematic symbolsComponent callouts
133T6C02 -- What is component 1 in figure T1? ResistorTransistorBatteryConnector
134T6C03 -- What is component 2 in figure T1? ResistorTransistorIndicator lampConnector
135T6C04 -- What is component 3 in figure T1? ResistorTransistorLampGround symbol
136T6C05 -- What is component 4 in figure T1? ResistorTransistorBatteryGround symbol
137T6C06 -- What is component 6 in figure T2? ResistorCapacitorRegulator ICTransistor
138T6C07 -- What is component 8 in figure T2? ResistorInductorRegulator ICLight emitting diode
139T6C08 --- What is component 9 in figure T2? Variable capacitorVariable inductorVariable resistorVariable transformer
140T6C09 -- What is component 4 in figure T2? Variable inductorDouble-pole switchPotentiometerTransformer
141T6C10 -- What is component 3 in figure T3? ConnectorMeterVariable capacitorVariable inductor
142T6C11 -- What is component 4 in figure T3? AntennaTransmitterDummy loadGround
143Electrical components Logic states Digital codes Traffic nodes T6C12 -- What do the symbols on an electrical circuit schematic diagram represent?Electrical componentsLogic statesDigital codesTraffic nodes
144Physical appearance of components T6C13 -- Which of the following is accurately represented in electrical circuit schematic diagrams?Wire lengthsPhysical appearance of componentsThe way components are interconnectedAll of these choices are correct
145Types of Radios and Radio Circuits Basic 2-Way Radio Station.
146Types 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.
147Types 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).
148Types 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.
149Types 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.
150Types 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.
151Types 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.
152Types of Radios and Radio Circuits Mixers.Mixers combine 2 different frequency signals together to produce 4 output frequencies.f1 x f2 f1, f2, f1-f2, & f1+f2.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.
153Phase splitter Mixer Inverter Amplifier T7A03 -- Which of the following is used to convert a radio signal from one frequency to another?Phase splitterMixerInverterAmplifier
154Reactance modulator Product detector Low-pass filter Oscillator T7A05 -- What is the name of a circuit that generates a signal of a desired frequency?Reactance modulatorProduct detectorLow-pass filterOscillator
155Impedance matching Oscillation Modulation Low-pass filtering T7A08 -- Which of the following describes combining speech with an RF carrier signal?Impedance matchingOscillationModulationLow-pass filtering
156Types 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.
157Types 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.
158Types 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.fLO > fRF.
159Types of Radios and Radio Circuits Receivers.Heterodyne receiver.
160Types 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.
161Types 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.
162Types 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.
163Total Harmonic Distortion T7A01 -- Which term describes the ability of a receiver to detect the presence of a signal?LinearitySensitivitySelectivityTotal Harmonic Distortion
164Discrimination ratio Sensitivity Selectivity Harmonic Distortion T7A04 -- Which term describes the ability of a receiver to discriminate between multiple signals?Discrimination ratioSensitivitySelectivityHarmonic Distortion
165High-pass filter Low-pass filter Transverter D. Phase converter T7A06 -- What device takes the output of a low-powered 28 MHz SSB exciter and produces a 222 MHz output signal?High-pass filterLow-pass filterTransverterD. Phase converter
166T7A11 -- Where is an RF preamplifier installed? Between the antenna and receiverAt the output of the transmitter's power amplifierBetween a transmitter and antenna tunerAt the receiver's audio output