Basic Communications Electronics T4

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Basic Communications Electronics T4

• The stuff radios are made of.

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First things first . Whats a circuit?
A circuit is a closed loop of wire with certain
electronic parts that will together perform a
specified function.Each part of the circuit is
represented by a symbol.
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Second thing Units Prefixes
giga G 109 1,000,000,000 mega M 106 1,000,000
kilo K 103 1,000 basic unit 100 1 milli m 10-
3 0.001 micro u 10-6 0.0000001 pico p 10-12 0
.000000000001
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T4E08 What is another way to specify the
frequency of a radio signal that is oscillating
at 1,500,000 Hertz? A. 1500 kHz B. 1500 MHz C.
15 GHz D. 150 kHz
Remember 1 kHz 1000 Hz
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DC and AC Power!
Direct Current Current is measured in Amperes.
Alternating Current
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Resistors
4 ohms
12 volts
3 Amps
Resistors limit the flow of current.
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Resistors
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Resistor Summary

• Resistors oppose (resist) the flow of current.
• Resistance is measured with an ohmmeter.
• The Unit of Measure of Resistance is the Ohm.

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T4A11 What is the term used to describe
opposition to current flow in ordinary conductors
such as wires? A. Inductance B. Resistance C.
Counter EMF D. Magnetism
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Inductors

• Inductors store electrical energy in their
  magnetic fields.
• The unit of measurement for inductors is the
  Henry.

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Capacitors
A capacitor is made by separating two
conductive plates by an insulator
or dielectric. Capacitors store
electrical energy in an electrostatic field. The
unit of capacitance is the farad.
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• CAPACITORS CAN HOLD
• A CHARGE
• FOR QUITE SOME TIME.
• They would be very happy to bite you.

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Units of Measurement

• Hertz Frequency (cycles per second)
• Volts Electromotive Force
• Amps Electrical Current
• Ohms Resistance (to current flow)
• Farads Capacitance
• Henries Inductors
• Watts Power (the work being done)

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Ohms Law

• Ohms Law is applicable to all electrical
  circuits.
• Ohms Law is a mathematical expression of the
  relationship between Voltage (EMF), Current (the
  flow of electrons in a circuit), and Resistance
  (to current flow).
• Expressed as E I x R

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Voltage and Current?

I
R
E
A
-
It is possible to have voltage without current,
as in the case of a battery by itself. In order
to have current, there must be an electrical path
(circuit) from the positive to the negative
terminal of the voltage source.
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Ohms Law
Electromotive Force, VOLTS
E
I
R
The flow of electrons AMPERES
Resistance to current flow OHMS
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Ohms Law
4 ohms
E / R I
3 ohms
2 ohms
As we change the resistance value, what happens
to the current flow in the circuit?
12/4 3
12/3 4
12/2 6
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T4D09 What is the voltage across the resistor if
a current of 2 amperes flows through a 10 ohm
resistor? A. 20 volts B. 0.2 volts C. 12
volts D. 8 volts
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T4D06 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.
0.667 amperes D. 1.5 amperes
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Power
Energy Expended, in WATTS
P
I
E
The flow of electrons AMPERES
Electromotive Force VOLTS
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Volts, Amps and Watts
4 ohms
12 volts
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The current in this circuit _________ Amps The
power in this circuit _________ Watts
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T4E07 How many milliamperes is the same as 1.5
amperes? A. 15 milliamperes B. 150
milliamperes C. 1500 milliamperes D. 15000
milliamperes
Remember 1 amp 1000 milliamps
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T4A09 Which of the following is a good electrical
conductor? A. Glass B. Wood C. Copper D. Rubber
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T4E01 What unit is used to describe electrical
power? A. Ohm B. Farad C. Volt D. Watt
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The Fuse

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The Fuse
A fuse will self destruct when current flow
exceeds the fuse rating. This results in an open
condition, and current flow will then cease,
saving equipment from overheating and possible
fire damage. When replacing a fuse, always use a
fuse which has the same current rating as the
fuse being replaced.
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T0A04 What is the purpose of a fuse in an
electrical circuit? A. To make sure enough power
reaches the circuit B. To interrupt power in
case of overload C. To prevent television
interference D. To prevent shocks
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T0A05 What might happen if you install a
20-ampere fuse in your transceiver in the place
of a 5-ampere fuse? A. The larger fuse would
better protect your transceiver from using too
much current B. The transceiver will run
cooler C. Excessive current could cause a fire
D. The transceiver would not be able to produce
as much RF output
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The Relationship of Frequency and Wavelength

• The distance a radio wave travels in one cycle is
  called wavelength.

V
One Cycle
0V
time
V-
One Wavelength
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Wavelength Formula

• To convert from frequency to wavelength
• Wavelength and Frequency are Inversely
  Proportional. As one goes up, the other must go
  down.

300 freq (MHz)
Wavelength
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On what amateur bands will you find these
frequencies?

• 50.125 MHz _______ meter band
• 21.25 MHz _______ meter band
• 145.21 MHz _______ meter band
• 7,233 kHz _______ meter band
• 28.350 MHz _______ meter band

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15
2
40
10
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T4B09 What property of a radio wave is often used
to identify the different bands amateur radio
operators use? A. The physical length of the
wave B. The magnetic intensity of the wave C. The
time it takes for the wave to travel one mile D.
The voltage standing wave ratio of the wave
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T1C08 What amateur band are you using if you are
operating on 223.50 MHz? A. 15 meter band B. 10
meter band C. 2 meter band D. 1.25 meter band
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Bandwidth
The amount of space a signal occupies in the
radio-frequency spectrum.
Ever listened to 97.1and you can hear
thestation at 96.9 and97.3? (thats 400 kHz!)
97.1 MHz
Broadcast FM is very messy (wide).
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Bandwidth -- AM SSB
We can hear most AMbroadcasts 5 kHz updown.
1080 kHz
AM Bandwidth 4 to 6 kHz SSB Bandwidth 2 to 3 kHz
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T6A09 What is the approximate bandwidth of a
single-sideband voice signal? A. 1 kHz B. 2
kHz C. Between 3 and 6 kHz D. Between 2 and 3 kHz
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Bandwidth of Amateur Signals
PSK31
50 Hz
200 Hz
RTTY
50 - 200 Hz
CW
2 3 kHz
SSB
AM
4 6 kHz
FM
10 20 kHz
(Not to scale!)
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T6A10 What is the approximate bandwidth of a
frequency-modulated voice signal? A. Less than
500 Hz B. About 150 kHz C. Between 5 and 15
kHz D. More than 30 kHz
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And Finally Power Sources!

• This power supply converts AC to DC.
• From 120 V
• To 13.8 V
• Generators convert engine power to electricity

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Batteries

• Batteries
• Cells typically supply 1.2 9 volts DC
• Cells may be connected in series to increase
  voltage.
• There are MANY different types of batteries.

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Rechargeable Batteries

• Nickel-Cadmium
• NiCd
• 1.2 V per cell
• 700 mAh per cell
• Nickel Metal Hydride
• NiMH
• 1.2 V per cell
• 1500 2200 mAh

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Rechargeable Batteries

• Lithium-Ion
• 3.3 3.6 V per cell
• 2100 2400 mAh
• Lead-Acid
• Car Batteries
• Gel-Cells
• 2.2 V per cell
• 35 75 Amp-hrs

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T4C08 What battery type on this list is not
designed to be re-charged? A. Nickel-cadmium B.
Carbon-zinc C. Lead-acid D. Lithium-ion
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T4C06 Which of the battery types listed below
offers the longest life when used with a
hand-held radio, assuming each battery is the
same physical size? A. Lead-acid B. Alkaline C.
Nickel-cadmium D. Lithium-ion
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Questions?