Download 3.0 - Electricity, Components and Circuits

Chapter 3
Electricity, Components and
Circuits
Fundamentals of Electricity
• When dealing with electricity, what we are
referring to is the flow of electrons through
a conductor.
• Electrons are negatively charged atomic
particles.
• A conductor is a material that allows electrons
to move with relative freedom within the
material.
• An insulator is a material that does not allow
electrons to move freely within the material.
Fundamentals of Electricity
• In electronics and radio, we control the flow
of electrons to make things happen.
• You need to have a basic understanding of
how and why we control the flow of
electrons so that you can better operate
your radio.
Basic Characteristics of Electricity
• There are three characteristics of electricity:
• Voltage
• Current
• Resistance
Basic Characteristics of Electricity
• Voltage
• Electromotive force (EMF) causing electrons to
flow
• a.k.a. – Electric potential
• Positive voltage attracts electrons
• Negative voltage repels electrons
• Measured in Volts (V)
Basic Characteristics of Electricity
• Current
• a.k.a. – Amperage
• Rate (quantity, not speed) at which electrons flow
• Measured in Amperes (A)
• Often shortened to “Amps”
• 1 Amp = 6.25 x 1018 electrons per second
• 6,250,000,000,000,000,000
Basic Characteristics of Electricity
• Resistance
• Opposition to flow of electrons
• Measured in Ohms (Ω)
Basic Characteristics of Electricity
• The flow of water through a hose is a good
analogy to understand the three
characteristics of electricity and how they
are related.
Characteristics of Electricity
are Inter-related
• Just like water flowing through a hose,
changes in voltage, current and resistance
affect each other.
• That effect is mathematically expressed in
Ohm’s Law.
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.
Ohm’s Law
• E = Electromotive Force
• Force causing electrons
to flow
• I = Current Intensity
E=IxR
I = E/R
R = E/I
• Number of electrons
flowing past a point in a
given period of time
• R = Resistance
• Opposition to flow of
electrons
T5A01 -- Electrical current is measured in
which of the following units?
A.
B.
C.
D.
Volts
Watts
Ohms
Amperes
T5A03 -- What is the name for the flow of
electrons in an electric circuit?
A.
B.
C.
D.
Voltage
Resistance
Capacitance
Current
T5A05 -- What is the electrical term for the
electromotive force (EMF) that causes electron
flow?
A.
B.
C.
D.
Voltage
Ampere-hours
Capacitance
Inductance
T5A07 -- Which of the following is a good
electrical conductor?
A.
B.
C.
D.
Glass
Wood
Copper
Rubber
T5A08 -- Which of the following is a good
electrical insulator?
A.
B.
C.
D.
Copper
Glass
Aluminum
Mercury
T5A11 -- What is the basic unit of electromotive
force?
A.
B.
C.
D.
The volt
The watt
The ampere
The ohm
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)
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 (R)
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)
The Electric Circuit:
An Electronic Roadmap
• For current to flow, there must be a path
from one side of the source of the current to
the other side of the source – this path is
called a circuit.
• There must be a hose (conductive path) through
which the water (current) can flow.
Types of Circuits
• Series Circuit.
• Provides one and only one path for current flow.
Types of Circuits
• Parallel Circuit
• Provides alternative paths for current flow.
Types of Circuits
• Short Circuit
• Direct connection between 2 points in a circuit
• Often unintentional
• Open Circuit
• No path from one side of the source of the
current to the other side of the source
• Often unintentional
Measuring Electricity
• Voltage is measured with a voltmeter.
• Connected in parallel with circuit.
• Current is measured with an ammeter.
• Connected in series with circuit.
Measuring Electricity
• Resistance is measured with an ohmmeter.
• Measurement is accomplished by applying a
known voltage, measuring the current, & using
Ohm’s Law to calculate the resistance.
• Power MUST be removed from circuit before
measuring!
• Component should be removed from circuit, if
possible.
The Multimeter
• The most common test instrument is the
Volt-Ohm-Milliammmeter (VOM) or
Multimeter.
• Measures voltage, current, or resistance.
• May have other functions.
The Multimeter
 The Multimeter
 Digital multimeter (DVM)


Very inexpensive.
Often has extra features in
addition to measuring volts,
amps, & ohms.
The Multimeter
 If resistance reading is initially very low but
slowly increases to a higher value, it
indicates the presence of a large
capacitance in the circuit.
 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.
T7D01 -- Which instrument would you use to
measure electric potential or electromotive
force?
A.
B.
C.
D.
An ammeter
A voltmeter
A wavemeter
An ohmmeter
T7D02 -- What is the correct way to connect a
voltmeter to a circuit?
A.
B.
C.
D.
In series with the circuit
In parallel with the circuit
In quadrature with the circuit
In phase with the circuit
T7D03 -- How is an ammeter usually connected to
a circuit?
A.
B.
C.
D.
In series with the circuit
In parallel with the circuit
In quadrature with the circuit
In phase with the circuit
T7D04 -- Which instrument is used to measure
electric current?
A.
B.
C.
D.
An ohmmeter
A wavemeter
A voltmeter
An ammeter
T7D05 -- What instrument is used to measure
resistance?
A.
B.
C.
D.
An oscilloscope
A spectrum analyzer
A noise bridge
An ohmmeter
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
T7D07 -- Which of the following measurements
are commonly made using a multimeter?
A.
B.
C.
D.
SWR and RF power
Signal strength and noise
Impedance and reactance
Voltage and resistance
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.
B.
C.
D.
The ohmmeter is defective
The circuit contains a large capacitor
The circuit contains a large inductor
The circuit is a relaxation oscillator
T7D11 -- Which of the following precautions
should be taken when measuring circuit
resistance with an ohmmeter?
A.
B.
C.
D.
Ensure that the applied voltages are correct
Ensure that the circuit is not powered
Ensure that the circuit is grounded
Ensure that the circuit is operating at the
correct frequency
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
Moving Electrons Doing
Something Useful
• Any time energy is expended to do
something, work is performed.
• When moving electrons do some work,
power is consumed.
• Unit of measurement of power is the Watt
(W).
Power
• Power is defined as the rate at which energy
is used to do work.
• It takes 10x more power to expend a given
amount of energy in 1 minute than it does to
expend the same amount of energy in 10
minutes.
Power Formula
• P = Power
P
Watts
E
I
Volts Amps
P=ExI
E=P/I
I=P/E
• Rate at which energy
is expended.
• E = Voltage
• I = Current
Two Basic Kinds of Current
• 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.
T5A02 -- Electrical power is measured in which of
the following units?
A. Volts
B. Watts
C. Ohms
D. Amperes
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
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
T5A10 -- Which term describes the rate at which
electrical energy is used?
A.
B.
C.
D.
Resistance
Current
Power
Voltage
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)
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.
B.
C.
D.
138 watts
0.7 watts
23.8 watts
3.8 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?
A.
B.
C.
D.
4.8 watts
30 watts
14.5 watts
0.208 watts
T5C11 -- How many amperes are flowing in a
circuit when the applied voltage is 12 volts DC
and the load is 120 watts?
A.
B.
C.
D.
0.1 amperes
10 amperes
12 amperes
132 amperes
T5A12 -- What term describes the number of
times per second that an alternating current
reverses direction?
A.
B.
C.
D.
Pulse rate
Speed
Wavelength
Frequency
Basic Electronic Components
 There are 3 basic types of components:

Resistor


Capacitor


Unit of measurement of resistance is the ohm (Ω).
Unit of measurement of capacitance is the farad
(F).
Inductor

Unit of measurement of inductance is the henry
(H).
The Resistor
• The function of the resistor is to reduce
(limit) the flow of current through it.
• Potentiometer.
• Volume Control
The Resistor
• A fixed amount of 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.
Capacitance
• Capacitance is the ability to store energy in
an electric field.
• The unit of measurement of capacitance is the
Farad (F).
• 1F is a very large value.
• Capacitors are commonly available in values ranging
from 1pF to a few hundred thousand microfarads.
The Capacitor
• The function of the capacitor is to
temporarily store electrical energy in an
electric field.
• Like a very temporary storage battery.
The Capacitor
•
•
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.
Inductance
• Inductance is the ability to store energy in a
magnetic field.
• The unit of measurement of inductance is the
Henry (H).
• Inductors are commonly available in values ranging
from 1µH to a few Henries.
The Inductor
• The function of the inductor is to
temporarily store electrical energy in a
magnetic field.
• Basically a coil of wire.
The Transformer
• One function of the transformer is to change
AC voltage levels.
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.
Components
Components
• Color Code.
• Bad Beer Rots Out Your Guts But
Veggies Go Well.
• Get Some Now (tolerance)
T5C01 -- What is the ability to store energy in an
electric field called?
A.
B.
C.
D.
Inductance
Resistance
Tolerance
Capacitance
T5C02 -- What is the basic unit of capacitance?
A.
B.
C.
D.
The farad
The ohm
The volt
The henry
T5C03 -- What is the ability to store energy in a
magnetic field called?
A.
B.
C.
D.
Admittance
Capacitance
Resistance
Inductance
T5C04 -- What is the basic unit of inductance?
A.
B.
C.
D.
The coulomb
The farad
The henry
The ohm
T6A01 -- What electrical component is used to
oppose the flow of current in a DC circuit?
A.
B.
C.
D.
Inductor
Resistor
Voltmeter
Transformer
T6A02 -- What type of component is often used as
an adjustable volume control?
A.
B.
C.
D.
Fixed resistor
Power resistor
Potentiometer
Transformer
T6A03 -- What electrical parameter is controlled
by a potentiometer?
A.
B.
C.
D.
Inductance
Resistance
Capacitance
Field strength
T6A04 -- What electrical component stores energy
in an electric field?
A.
B.
C.
D.
Resistor
Capacitor
Inductor
Diode
T6A05 -- What type of electrical component
consists of two or more conductive surfaces
separated by an insulator?
A.
B.
C.
D.
Resistor
Potentiometer
Oscillator
Capacitor
T6A06 -- What type of electrical component stores
energy in a magnetic field?
A.
B.
C.
D.
Resistor
Capacitor
Inductor
Diode
T6A07 -- What electrical component is usually
composed of a coil of wire?
A.
B.
C.
D.
Switch
Capacitor
Diode
Inductor
T6D06 -- What component is commonly used to
change 120V AC house current to a lower AC
voltage for other uses?
A.
B.
C.
D.
Variable capacitor
Transformer
Transistor
Diode
Reactance & 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.
• Special kind of resistance to the flow of AC
called reactance (X).
• Reactance also measured in Ohms (Ω).
Reactance & 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.
ELI the ICEman
Reactance & Impedance
• Opposition to AC current flow in capacitors
or inductors is called reactance (X, XC, or XL).
• Reactance is also measured in Ohms (Ω).
Reactance & Impedance
• Combination of resistance and reactance is
called impedance (Z).
• Impedance also measured in Ohms (Ω).
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.
Resonance
• This condition is called resonance.
• Resonant circuit.
• Tuned circuit.
• Impedance of a resonant circuit is purely
resistive.
• Reactance = 0Ω
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
T5C13 -- What are the units of impedance?
A. Volts
B. Amperes
C. Coulombs
D. Ohms
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
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
Break
Protective Components –
Intentional Open Circuits
• Fuses and circuit breakers are designed to
interrupt the flow of current if the current
becomes to large
• Fuses blow – one time protection
• Circuit breakers trip – can be reset and
reused
The Switch
• The function of the switch is to turn on or off
or to redirect the flow of current.
The Relay
• A relay is an electrically-controlled switch.
• A set of switch contacts connected to an
electromagnet.
The Meter
• A meter displays an electrical value on a
numeric scale.
• All analog meters are ammeters.
• A voltmeter is an ammeter with a series resistor.
T6A09 -- What electrical component is used to
protect other circuit components from current
overloads?
A.
B.
C.
D.
Fuse
Capacitor
Inductor
All of these choices are correct
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
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
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
T6D02 -- Which best describes a relay?
A. A switch controlled by an electromagnet
B. A current controlled amplifier
C. An optical sensor
D. A pass transistor
T6D04 -- Which of the following can be used to
display signal strength on a numeric scale?
A.
B.
C.
D.
Potentiometer
Transistor
Meter
Relay
The Diode
• The function of the diode is to allow the
flow of current in only one direction.
• An analogy, a check valve in a water system.
The Diode
• One use of a diode is as a rectifier in a
power supply circuit to convert an AC
voltage into a varying DC voltage.
The Diode
• Light-Emitting Diode (LED).
• Emits light when forward-biased.
The Transistor
• 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.
NPN
PNP
The Transistor
• Bipolar Transistors.
• Small change in base current results in large
change in emitter current.
• Low input & output impedances.
The Transistor
• Field-Effect Transistors (FET).
• Small change in gate voltage results in large
change in drain current.
• High input impedance & low output impedance.
The Integrated Circuit
• The integrated circuit is a collection of
components contained in one device that
accomplishes a specific task.
• Acts like a “black-box”
T6B01 -- What class of electronic components is
capable of using a voltage or current signal to
control current flow?
A.
B.
C.
D.
Capacitors
Inductors
Resistors
Transistors
T6B02 -- What electronic component allows
current to flow in only one direction?
A.
B.
C.
D.
Resistor
Fuse
Diode
Driven element
T6B03 -- Which of these components can be used
as an electronic switch or amplifier?
A.
B.
C.
D.
Oscillator
Potentiometer
Transistor
Voltmeter
T6B04 -- Which of the following components can
be made of three layers of semiconductor
material?
A.
B.
C.
D.
Alternator
Transistor
Triode
Pentagrid converter
T6B05 -- Which of the following electronic
components can amplify signals?
A.
B.
C.
D.
Transistor
Variable resistor
Electrolytic capacitor
Multi-cell battery
T6B06 -- How is the cathode lead of a
semiconductor diode usually identified?
A.
B.
C.
D.
With the word cathode
With a stripe
With the letter C
All of these choices are correct
T6B07 -- What does the abbreviation LED stand
for?
A.
B.
C.
D.
Low Emission Diode
Light Emitting Diode
Liquid Emission Detector
Long Echo Delay
T6B08 -- What does the abbreviation FET stand
for?
A.
B.
C.
D.
Field Effect Transistor
Fast Electron Transistor
Free Electron Transition
Field Emission Thickness
T6B09 -- What are the names of the two
electrodes of a diode?
A.
B.
C.
D.
Plus and minus
Source and drain
Anode and cathode
Gate and base
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
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
T6B12 -- What is the term that describes a
transistor’s ability to amplify a signal?
A.
B.
C.
D.
Gain
Forward resistance
Forward voltage drop
On resistance
T6D01 -- Which of the following devices or circuits
changes an alternating current into a varying
direct current signal?
A.
B.
C.
D.
Transformer
Rectifier
Amplifier
Reflector
T6D07 -- Which of the following is commonly used
as a visual indicator?
A.
B.
C.
D.
LED
FET
Zener diode
Bipolar transistor
T6D09 -- What is the name of a device that
combines several semiconductors and other
components into one package?
A.
B.
C.
D.
Transducer
Multi-pole relay
Integrated circuit
Transformer
Other Circuit Symbols
Putting It All Together in a
Circuit Diagram
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
T6C01 -- What is the name for standardized
representations of components in an electrical
wiring diagram?
A.
B.
C.
D.
Electrical depictions
Grey sketch
Schematic symbols
Component callouts
T6C13 -- Which of the following is accurately
represented in electrical circuit schematic
diagrams?
A.
B.
C.
D.
Wire lengths
Physical appearance of components
The way components are interconnected
All of these choices are correct
The Basic Radio Station
Circuits Used in Radios
• Transmit/Receive (TR) Switch
• If the station antenna is shared between the
transmitter and receiver, the TR switch allows
the antenna to be switched to the transmitter
when sending and to the receiver when
receiving.
• In a transceiver, the TR switch is inside the unit and
requires no attention from the operator.
Circuits Used in Radios
• Oscillators
• An oscillator produces a steady AC voltage on a
single frequency.
• Used in both receivers & transmitters to determine
operating frequency.
• Variable-frequency oscillator (VFO).
Circuits Used in Radios
• Amplifiers
• An amplifier increases 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.
Simple CW Transmitter
Block Diagram
Circuits Used in Radios
• Filters
• Filters reject (attenuate) unwanted signals.
• Passive filters.
• Capacitors, inductors, & resistors.
• Tuned circuits are common examples of passive filters.
• Active filters
• Amplifiers with circuits to reject unwanted signals.
• Can have gain.
Circuits Used in Radios
• Filter classifications.
•
•
•
•
Low pass.
High pass.
Band pass.
Band reject (notch).
Circuits Used in Radios
• Mixers.
• Mixes 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.
Circuits Used in Radios
• Modulators
• Encode information (voice, data, etc.) onto an RF
signal (carrier)
• Can be as simple as on-off switch
• Telegraph key
• Can be very complex
Circuits Used in Radios
• Demodulators
• Extracts information (voice, data, etc.) from RF
signal (carrier)
• Several different types of demodulators used in
amateur radio equipment depending on type of
modulation being used
Circuits Used in Radios
• Simple detectors
• Envelope detector used to demodulate AM
signals
• Product detectors
• One application of a mixer circuit
• Used to demodulate CW & SSB signals
• Frequency discriminators
• Used to demodulate FM signals
Receivers
• Types:
• Direct Conversion.
• 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
• Types:
• Heterodyne.
• 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.
Superheterodyne Receiver
Block Diagram
Superheterodyne Receiver
• Single-conversion.
• One mixer.
• One IF frequency.
• Double-conversion.
• Two mixers.
• Two IF frequencies.
• 2nd IF frequency very low for easier filtering.
• 2nd IF typically 455 kHz.
• Not used much any more.
FM Receiver Block Diagram
RF
Amp
Mixer
Filter
IF
Amp
Limiter
Osc
Frequency
Discriminator
Audio
Amp
Spkr
Receivers
• Two primary characteristics:
• Sensitivity.
• Ability to receive weak signals.
• Sometimes a pre-amplifier (pre-amp) is added between
antenna & receiver to improve sensitivity.
• Selectivity.
• Ability to reject unwanted signals.
Transverter
• Converts a band of frequencies to a different
band of frequencies.
• Both transmit and receive.
• Usually used for VHF/UHF/SHF/EHF operation.
• Driven by a low-power signal from an HF
transceiver (typically 28 MHz).
• Amateur Satellites.
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
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
T7A04 – Which terms describes the ability of a
receiver to discriminate between multiple signals?
A.
B.
C.
D.
Discrimination ratio
Sensitivity
Selectivity
Harmonic Distortion
T7A05 -- What is the name of a circuit that
generates a signal of a desired frequency?
A.
B.
C.
D.
Reactance modulator
Product detector
Low-pass filter
Oscillator
T7A08 -- Which of the following describes
combining speech with an RF carrier signal?
A.
B.
C.
D.
Impedance matching
Oscillation
Modulation
Low-pass filtering
T7A06 -- What device takes the output of a lowpowered 28 MHz SSB exciter and produces a 222
MHz output signal?
A.
B.
C.
D.
High-pass filter
Low-pass filter
Transverter
Phase converter
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
Questions?