Electrical and RF Safety T0 3 Questions Important

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Electrical and RF Safety (T0)3 Questions --
Important!

• Cant touch this (at least not while it

is transmitting)
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Grounding Your Station
All radio station equipment must be properly
grounded, separate from the ground for the
houses AC electrical distribution system. If the
grounding is not kept separate, reflected radio
frequency energy in the form of standing waves
can be conducted into the electrical wiring of
the building and into neighborhood power
distribution lines.
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Grounding Diagram
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Just be careful where you dig!

• Watch for
• Water Mains
• Sewer
• Telephone
• Otherwise, well

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Station Grounding

• Use only copper or galvanized rods
• Eight feet into the ground
• Connect to equipment with copper braid
• Make connections as short as possible!
• Ground ALL your equipment.
• Do not use plumbing for ground.
• Make sure all connections are tight!

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T0A06 What is a good way to guard against
electrical shock at your station? A. Use 3-wire
cords and plugs for all AC powered equipment B.
Connect all AC powered station equipment to a
common ground C. Use a ground-fault interrupter
at each electrical outlet D. All of these answers
are correct
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T0A01 What is a commonly accepted value for the
lowest voltage that can cause a dangerous
electric shock? A. 12 volts B. 30 volts C. 120
volts D. 300 volts
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T0A02 What is the lowest amount of electrical
current flowing through the human body that is
likely to cause death? A. 10 microamperes B.
100 milliamperes C. 10 amperes D. 100 amperes
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Common Sense will tell you a lot when it comes to
RF Safety.
Common sense saves lives answers a lot of test
questions!
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T0A07 What is the most important thing to
consider when installing an emergency disconnect
switch at your station? A. It must always be as
near to the operator as possible B. It must
always be as far away from the operator as
possible C. Everyone should know where it is and
how to use it D. It should be installed in a
metal box to prevent tampering
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T0A13 What kind of hazard might exist in a power
supply when it is turned off and disconnected?
A. Static electricity could damage the
grounding system B. Circulating currents inside
the transformer might cause damage C. The fuse
might blow if you remove the cover D. You might
receive an electric shock from stored charge in
large capacitors
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RF Safety for Dummies

• Install your antenna away from people, especially
  your neighbors. The higher the better.
• Make sure your antenna is not near or could fall
  on a power line.
• Keep your hands and other body parts away from
  the antenna and feed lines.

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T0B01 Why should you wear a hard hat and safety
glasses if you are on the ground helping someone
work on an antenna tower? A. It is required by
FCC rules B. To keep RF energy away from your
head during antenna testing C. To protect your
head and eyes in case something accidentally
falls from the tower D. It is required by the
electrical code
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2 Types of Radiation

• Ionizing
• Gamma and X-ray
• Can cause ionization of atomic structure
• Not good for your DNA
• Non-ionizing
• Radio waves
• Can cause heating of biological tissue
• If sufficient energy is present, can cause burns

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Power Density

• Measured in milli-watts per square centimeter
• The rules are most stringent between 30 MHz and
  300 MHz.

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Duty Cycle

• How much of the time is the transmitter
  operating?
• AM 100
• FM 100
• SSB 20
• CW 50

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T0C11 Why is duty cycle one of the factors used
to determine safe RF radiation exposure
levels? A. It takes into account the amount of
time the transmitter is operating B. It takes
into account the transmitter power supply
rating C. It takes into account the antenna feed
line loss D. It takes into account the thermal
effects of the final amplifier
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RF Heating

• Radio waves can heat body tissue.
• Works exactly like your microwave oven.
• The area most likely to be injured is the eye as
  it lacks sufficient blood flow for cooling.
• The eye can form cataracts from repeated exposure
  to high levels of RF energy.
• NEVER touch an antenna or other RF source. You
  could be severely burned.

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T0C07 What could happen if a person accidentally
touched your antenna while you were transmitting?
A. Touching the antenna could cause television
interference B. They might receive a painful RF
burn injury C. They would be able to hear what
you are saying D. Nothing
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Controlled and Uncontrolled Environments

• Controlled Environments
• The amateur operators household and property
• Persons here are aware of RF risks, and have
  control of the transmitting equipment.
• Uncontrolled Environments
• Your neighbors household and property
• Persons here are generally not aware of RF risks
  and have NO control over the transmitter.

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Exposure Averaging Times

• Controlled Environments
• The exposure averaging time is
• 6 Minutes
• Uncontrolled Environments
• The exposure averaging time is
• 30 Minutes

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3 Methods of RF Checking

• Measure the RF fields
• requires costly equipment that you dont have
• Calculate the RF fields
• requires complex software that you dont have
• Use the charts published by the FCC
• The charts are free
• Fairly simple to use

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Who is Exempt?

• The RF safety regulations do not apply to
• Mobile equipment
• Hand-held radios
• Any station that produces less than 50 watts PEP

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T0C04 What factors affect the RF exposure of
people near an amateur transmitter? A. Frequency
and power level of the RF field B. Distance from
the antenna to a person C. Radiation pattern of
the antenna D. All of these answers are correct
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T0C03 What is the maximum power level that an
amateur radio station may use at frequencies
above 30 MHz before an RF exposure evaluation is
required? A. 1500 watts PEP transmitter
output B. 1 watt forward power C. 50 watts PEP at
the antenna D. 50 watts PEP reflected power
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One last word about safety
Lightning is a REAL threat! Never take it
for granted.
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Lightning Protection

• Ground your equipment properly.
• Disconnect your equipment during storms.
• Install lightning arrestors between the feed line
  and the ground.
• These devices short the charge into the ground
  avoiding your expensive equipment!

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T0A08 What precautions should be taken when a
lightning storm is expected? A. Disconnect the
antenna cables from your station and move them
away from your radio equipment B. Unplug all
power cords from AC outlets C. Stop using your
radio equipment and move to another room until
the storm passes D. All of these answers are
correct
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Like we said, common sense when it comes to RF
safety!
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Questions?