Radio Merit Badge Amateur Radio Option

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Radio Merit Badge(Amateur Radio Option)

• James Alderman
• KF5WT

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Class Format

• Session I Intro To Radio
• Session II Electronic Components Safety
• Session III Amateur Radio Emergency
  Communications

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Class Format

• Session II
• Electronic Components Safety

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Components
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Old Timey Components
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Basic Electrical Terms

• Conductor substance through which electricity
  flows easily (copper, silver, gold)
• Insulator substance through which electricity
  does not flow easily (glass, rubber, plastic)

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Types of Electrical Current

• Direct Current (DC) flows only one direction
  produced by battery
• Alternating Current (AC) flows in first one
  direction then another found in our home
  electrical outlets

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Basic Electrical Terms

• Voltage electrical pressure (volts)
• Current the flow of electricity through a
  circuit (amps)
• Power the ability to do work (watts)

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Block Diagram vs. Schematic
Radio Transmitter
Block Diagram Outlines the various functions
within an electronic device
RF Oscillator
Carrier Signal
Pre Amp
Final Amp
Input
Output
Audio Signal
Modulated RF Signal
Mixer
Switch
120 ohm

Schematic Diagram Uses standard electrical
symbols to describe an electrical circuit in
detail
3V
LED flashlight
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Radio Block Diagram
RF Oscillator
Carrier Signal
Pre Amp
Final Amp
TX
Feed Line
Audio Signal
Modulated RF Signal
Antenna
Microphone
Mixer
RX
Transmitter
Receiver
RF/IF Oscillator
Reference Frequency
Pre Amp
Output Amp
Tuner
Audio Signal
Modulated RF Signal
Speaker
Detector
Transceiver
Volume Control
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Open Circuit
When S1 is open current can not flow. This is
an OPEN Circuit.
S1
120 ohm

3V
LED flashlight
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Closed Circuit
When S1 is closed current flows and the
LED Lights up. This is a CLOSED Circuit
S1
120 ohm

Current Flow
3V
LED flashlight
13
Short Circuit
If S1 gets broken and the contacts touch the case
of the flashlight, the result could cause current
to flow out of control through an unintended
path. This is a SHORT circuit.
S1
120 ohm

Abnormally High Current Flow
3V
LED flashlight
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Circuit Experiment
Draw This Diagram In Your Workbook
Fuse
SPDT Switch

Battery
Bulb

• This Experiment Demonstrates
• Open Circuit
• Closed (complete) Circuit
• Short Circuit

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Schematic Symbols
Draw Schematic Symbols In Your Workbook

SPDT Switch
N.O. Push button
SPST Switch
Light-Emitting Diode
Battery
Capacitor
Inductor
Transformer
Diode
NPN Bipolar Transistor (BJT)
PMOS Field Effect Transistor (FET)
Variable Capacitor
Variable Resistor (Potentiometer)
AC Voltage Source
OpAmp
Earth Ground
Circuit Ground
Incandescent Lamp
Speaker/Mic
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Properties
Record These In Your Workbook
Resistor opposes or resists current
flow measured in ohmsCapacitor stores energy
in electric field measured in faradsInductor
stores energy in a magnetic field measured in
henries
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Safety With RF Energy

• Never operate radios with the cover off
• Exposure to high levels of RF can cause burns and
  cancer
• Human eyes especially sensitive to RF
• Hams required to conduct a routine station
  evaluation to verify safe operation (usually
  done by consulting a chart)

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Safety With Electricity

• Minimum fatal voltage 30 volts
• Minimum fatal current if passed through the human
  heart 1/10th of an amp
• Power lines are un-insulated and carry thousands
  of volts never touch them!

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Electricity Through the Body
Through Heart !
Through Hand
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Electric Power
Power Generating Plant
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Electric Power
Transmission Lines (carry from 300,000 up to
several million volts)
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Electric Power
Substation (Millions of volts in 14,000 volts
out)
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Electric Power
Distribution Lines and Customer Transformer
14,000 volt primary distribution lines
Transformer (Converts 14,000 volts down to 240
and 120 volts)
240 / 120 volt lines to house
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The Future of Power Generation
India Proposes Beaming Solar Power Down From Space
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The Future of Power Generation
Each satellite 1.5 miles across Produces 1
Gigawatt of power (Enough to power 500,000
homes) More than double the output of a typical
coal-fired plant
Japan Is Already Building One ! (PopSci July
2008, p 42)
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The Power In Power Lines

• TXU Energy Show Winter Camp 2004

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Substation Video
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Boy Meets Power Lines

• Boys Arms Amputated After Shock From Cable
• GENOA, Ark. Doctors amputated both arms of a
  13-year-old boy below the elbow after he
  sustained a shock from an electrical distribution
  cable. David Letterman, 13, of Genoa underwent
  surgery at Arkansas Childrens Hospital, his
  family said. David and his friend, Cody Sims,
  11, were walking a power line right-of-way with
  the idea of bow hunting before church when they
  came upon a tree that had fallen on an electrical
  cable. David wanted to remove the dead tree from
  the line because he saw it smoking and was afraid
  it would catch fire.
• Dallas Morning News Thursday, October 9, 2003,
  page 3A

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Ground-Mounted Transformers
Sinking Transformer reported to power company

• Photo Courtesy of Standard Utilities Ft. Worth,
  Texas

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Ground-Mounted Transformers
Neighborhood kids had tunneled under transformer

• Photo Courtesy of Standard Utilities Ft. Worth,
  Texas

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Ground-Mounted Transformers
Input 14,000 volts Output 240 volts to
FOUR homes

• Photo Courtesy of Standard Utilities Ft. Worth,
  Texas

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Ground-Mounted Transformers
Note playground ball inches from primary terminals

• Photo Courtesy of Standard Utilities Ft. Worth,
  Texas

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If Power Lines Strike Your Car

• Stay inside and call for help
• Power lines can re-energize automatically. Never
  assume they are dead.
• If car catches fire, jump out on both feet and
  scoot away.

Boom Truck In Power Lines Video Clip
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Antennas Towers
Never place antennas or feed lines

• OVER or UNDER power lines
• Where they could fall on a power line in any
  direction
• Where a person could touch the antenna

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Lightning Protection

• Antenna pole connected to ground rod
• Disconnect radios if lightning is in the area
• Disconnect radios when not in use
• Connect antennas to ground when not in use

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Grounding Your Station
Common ground point Fuse or circuit breaker
Safety interlock on high voltage supplies
Everyone in your house should know how to shut
off the power
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Hybrid Cars

• Main batteries - 200 to 300 volts DC at hundreds
  of amps
• With car switched on, main power lines carry 300
  to 600 volts AC, three phase

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Installing A Radio In A Hybrid
Get help from an adult !
Only connect to auxiliary battery
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Future Hybrid Car

• Plug-in Hybrid
• Travels 40 miles on battery power alone
• Gets 53 MPG
• Recharges in 6 hours
• Available 2010

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Radio Merit Badge 10 Minute Break
Proceed to next session