Safety

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Chapter 9

• Safety

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Chapter 9 Safety

• Todays agenda
• Working safely with electricity
• Safety grounding
• Lightning protection
• RF exposure rules
• Evaluating your station
• Reducing exposure to RF

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Chapter 9 Safety

• Todays agenda (Continued)
• Safely installing antennas
• Working on and around towers

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Chapter 9 Safety
There is nothing particularly risky about working
with electricity, antennas, or climbing
towers. Compared to many activities, amateur
radio is one of the safest hobbies because most
hams educate themselves about safety and follow
some simple rules and heres where it gets
dangerous --- they use common sense and
unfortunately, common sense is not distributed
equally across the gene pool.
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Chapter 9 Electrical Safety
Working safely with electricity mostly means
avoiding contact with it. Compared to many
activities, amateur radio is one of the safest
hobbies because most hams educate themselves
about safety and follow some simple rules.
Sometimes a little common sense goes a long way.
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Chapter 9 Electrical Safety
Electrical Injuries

• Electrical hazards produce two types of injury
• Shocks and
• Burns
• Whenever electricity flows through any part of
  your body both can occur.
• Shocks and burns can be caused by ac or dc and
  result from current flow through the body.

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Chapter 9 Electrical Safety
Electrical Injuries
Effects of Electric Current in the Human Body Effects of Electric Current in the Human Body
Current Reaction
Below 1 milliampere Generally not perceptible
1 milliampere Faint tingle
5 milliamperes Slight shock not painful but disturbing Average person cannot let go
6-25 milliamperes (Women) 9-30 milliamperes (Men) Painful shock, loss of muscular control cant let go range.
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Chapter 9 Electrical Safety
Electrical Injuries
Effects of Electric Current in the Human Body Effects of Electric Current in the Human Body
50-150 milliamperes Extreme pain respiratory arrest severe muscular contractions death is possible.
1000-4300 milliamperes Heart pumping ceases muscular contraction and nerve damage death likely.
10,000 milliamperes Cardiac arrest severe burns death probable
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Chapter 9 Electrical Safety
Electrical Injuries

• The most dangerous currents are those that flow
  through the heart
• Hand-to-hand
• Hand-to-foot
• A current of 100 mA or more can disrupt normal
  heart rhythm.
• Voltages as low as 30 volts can cause enough
  current flow to be dangerous.

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Chapter 9 Electrical Safety
Electrical Injuries

• Electrical hazards produce two types of injury
• Shocks and
• Burns
• Whenever electricity flows through any part of
  your body both can occur.
• Shocks and burns can be caused by ac or dc and
  result from current flow through the body.

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Chapter 9 Electrical Safety
Avoiding Electrical Hazards

• Never work on live equipment unless it is
  absolutely necessary (e.g., Troubleshooting or
  testing).
• Never assume equipment is off or de-energized.
  Check with a meter or tester first.
• Capacitors in a power supply can store hazardous
  voltage after the charging circuit is turned off.
• Test with a meter
• Use a grounding stick to shunt the charge to
  ground.

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Chapter 9 Electrical Safety
Avoiding Electrical Hazards

• If you have to work on live equipment follow
  these guidelines
• Keep one hand in your pocket when probing or
  testing energized equipment.
• Never bypass a safety interlock unless
  specifically instructed to do so.
• Remove your jewelry when working on electronics.

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Chapter 9 Electrical Safety
Response to Electrical Injury
If you or someone receives an electrical
shock Turn off the power dont touch the
person while they are in contact with electricity
or you will be the next victim. Install a
clearly-labeled master ON/OFF switch for the
circuit to your ham shack. Show your family how
to turn off power at the switch AND at the
circuit breaker box. You and your family should
consider learning CPR and first aid for
electrical injuries.
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Chapter 9 Electrical Safety
AC Safety Grounding

• Most ham stations DO NOT require new wiring and
  can operate safely when powered from your homes
  ac wiring. You just have to follow some simple
  guidelines
• Use three-wire power cords that connect the
  chassis of your equipment to the ac safety
  ground.
• Use Ground Fault Circuit Interrupter (GFCI)
  circuit breakers.
• Use a circuit tester to verify proper wiring

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Chapter 9 Electrical Safety
AC Safety Grounding

• NEVER replace a fuse or circuit breaker with
  one of a larger size.
• Dont overload single outlets.
• If new wiring is required, hire an electrician
  do it or at least inspect your work.
• Be sure to follow the Hot-Black (occasionally
  Red), Neutral-White, Ground-Green (or bare
  wire) wiring standard

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Chapter 9 Electrical Safety
AC Safety Grounding

• Use cable and wire sufficiently rated for the
  expected current load.
• Use the proper size fuses and circuit breakers.
• If you build your own equipment, always install
  a fuse or circuit breaker IN SERIES with the ac
  hot conductor.

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Chapter 9 Electrical Safety
RF Burns
RF burns result from contact with a hot spot
a location where high RF voltage is present on
the outside of a connector, cable or equipment
enclosure. The RF voltage creates currents in
the skin at the point of contact. Can be painful
but dont do much damage Using a common ground
all of the radio equipment at the same RF voltage
thereby minimizing hot spots and the
possibility of a burn.
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Chapter 9 Electrical Safety
Lightning

• Lightning strikes amateur towers and antennas NO
  MORE frequently than tall trees or other
  structures.
• However, common sense must prevail and there are
  some things you should do regardless of where you
  live.
• Ground all towers, masts and antenna mounts
• Ground at the base or if roof-mounted, use a
  large diameter wire to a ground rod.
• Ground connections should be as short as
  possible and avoid sharp bends.

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Chapter 9 Electrical Safety
Lightning

• When lightning is anticipated, disconnect all
  cables outside the house.
• Unplug equipment power cords inside the house.
• Operating during a thunderstorm is never a good
  idea.
• A nearby strike can create a voltage surge of
  thousands of volts in a power line or phone line.

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Chapter 9 RF Exposure
After many studies done at power line frequencies
(50 and 60 Hz) and radio frequencies of RF
(shortwave, including amateur frequencies and
mobile phone), NO LINK has been established
between low-level electromagnetic radiation and
health risks. At the relatively low frequencies
used by radio amateurs, RF energy is
non-ionizing radiation.
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Chapter 9 RF Exposure
Despite a lack of evidence that radio frequencies
(RF) pose a health risk, its a good idea to
avoid unnecessary exposure to high levels of
RF. The FCC has set limits on the Maximum
Permissible Exposure (MPE) from radio
transmitters of any sort. Hams are required to
evaluate their stations to see if their operation
has the potential to exceed MPE levels. RF
energy can ONLY cause injury to the human body IF
the combination of frequency and power causes
excessive energy to be absorbed.
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Chapter 9 RF Exposure

• There are two techniques to ensure that humans
  are not exposed to high-strength fields of RF
  energy
• Prevent access to locations where strong fields
  are present.
• Make sure strong fields are not created in or
  directed towards areas where people might be
  present.
• RF burns can be eliminated by proper grounding
  techniques or by preventing access to an antenna.

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Chapter 9 RF Exposure

• When the human body absorbs RF energy, heating
  occurs.
• RF energy causes the molecules in the body to
  vibrate at the same frequency.
• The energy of the vibration is dissipated as
  heat.
• Absorption of RF energy varies with the frequency
  because the body absorbs more RF energy at some
  frequencies than others. The human body absorbs
  more RF energy at VHF frequencies than any other
  part of the RF spectrum.

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Chapter 9 RF Exposure

• The intensity of an RF field is called power
  density.
• Measured in several ways
• Most common is milliwatts per square
  centimeters (mW/cm2)
• Power density is highest near antennas and in the
  directions where antennas have the most gain.
  Its also very high inside transmitting
  equipment.
• Increasing transmitter power increases power
  density everywhere around an antenna.

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Chapter 9 RF Exposure
The further away you are from an antenna the
lower the power density in proportion to the
square of the distance from the antenna. At
twice the distance from the antenna, power
density is divided by four. Controlling the
power and distance, forms the basis for amateur
RF safety.
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Chapter 9 RF Exposure
The FCC has established safe levels of RF
exposure Maximum Permissible Exposure (MPE)
levels. MPE and absorption rates vary with
frequency. Absorption rates vary with the size
of the body or body part and is highest where the
body is naturally resonant. The full body is
resonant at about 35 MHz if grounded and about 70
MHz if not grounded. Body parts are resonant at
higher frequencies (e.g., an adults head is
resonant at about 400 MHz).
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Chapter 9 RF Exposure
Above and below the ranges of highest absorption,
the body less and less to the RF energy. The
highest absorption rates are above the HF portion
of the RF spectrum 30 to 1500 MHz. The highest
RF energy is at VHF frequencies (30-300 MHz)
regardless of whether it is a controlled or
uncontrolled environment.
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Chapter 9 RF Exposure

• In a controlled environment people are aware of
  the their exposure and can take the necessary
  steps to minimize it
• Wear hats and blankets made of aluminum foil
• Sit in a lead-lined room below ground
• Attach grounding wires to your big toes
• On a serious note, the FCC has determined that
  the controlled environment generally applies to
  amateur operators, their family members and their
  guests and is limited to your home and property.

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Chapter 9 RF Exposure
People in uncontrolled environments are not
aware of their exposure areas open to the
general public and your neighbors property and
their risk of exposure is generally less than in
controlled environments. Note Even in
uncontrolled environments, wearing aluminum
foil hats is strongly recommended.
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Chapter 9 RF Exposure

• Exposure limits are based on averages rather than
  peak exposure.
• The averaging period for controlled
  environments is 6 minutes.
• The averaging period for uncontrolled
  environments is 30 minutes
• The difference in averaging periods reflects the
  difference in how long people are expected to be
  present and exposed.

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Chapter 9 RF Exposure
Duty cycle is the ratio of the transmitted
signals on-the-air time to the total operating
time during the measurement period. The maximum
is 100 For most amateur contacts, the
transmitter is keyed no more than 50 of the time
and usually much less which in turn lowers the
duty cycle of the emissions. Because duty
cycle affects the average power level of
transmissions, it must be considered when
evaluating exposure.
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Chapter 9 RF Exposure

• Antenna Gain is the last piece of the puzzle that
  we must consider.
• Beam antennas focus radiated power toward one
  direction which results in increased gain.
  Therefore, gain increases your average power in
  the preferred direction.
• There are four factors that affect RF exposure
• Transmitter power
• Frequency
• Distance to the antenna
• Radiation pattern of the antenna

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Chapter 9 RF Exposure

• With the exception of mobile and hand held
  transceivers, the FCC requires all fixed stations
  be evaluated for RF exposure.
• The use of special equipment and computer
  modeling are acceptable but are too expensive or
  too much effort is required.
• Most evaluations use the techniques outlined in
  the FCCs Office of Engineering Technology (OET)
  Bulletin 65.
• Uses tables and simple formulas to determine if
  your station has the potential of causing an
  exposure hazard.

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Chapter 9 RF Exposure
Once youve done an evaluation you do not need to
do another unless you change equipment that
affects the average output power (e.g. added an
amplifier or increased antenna gain). Youll
also need to reevaluate if you add a new
frequency band. If your transmitted power (PEP)
is less than the levels indicated below on the
frequencies you operate, then no evaluation is
required. The FCC has determined that the risk
of exposure from those levels is too small to
create an exposure risk
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Chapter 9 RF Exposure
Power Thresholds for RF Exposure Evaluation Power Thresholds for RF Exposure Evaluation Power Thresholds for RF Exposure Evaluation Power Thresholds for RF Exposure Evaluation Power Thresholds for RF Exposure Evaluation Power Thresholds for RF Exposure Evaluation
Band Watts Band Watts Band Watts
160 m 500 15 m 100 70 cm 70
80 m 500 12 m 75 33 cm 150
40 m 500 10 m 50 23 cm 200
30 m 425 6 m 50 13 cm 250
20 m 225 2 m 50 SHF (all bands) 250
17 m 125 1.25 m 50 SHF (all bands) 250
If you need to do an evaluation, you can use
on-line exposure calculators and pre-calculated
tables. Youll need to know the frequency and
power level, distance from the antenna and the
antennas radiation pattern.
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Chapter 9 RF Exposure
If you need to do an evaluation, you can use
on-line exposure calculators and pre-calculated
tables. Whichever method used, youll need to
know the frequency and power level, distance from
the antenna and the antennas radiation
pattern. Conduct the evaluation for each
frequency band and antenna used on that band.
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Chapter 9 RF Exposure

• So what do you do if you find a potential hazard?
• You could issue everyone a hat made of aluminum
  foil or
• Locate antennas away from where people can get
  close to them you dont want anyone to be able
  to touch the antenna.
• Raise the antenna it usually improves your
  signal as well as being a good safety practice.
• Avoid aiming a beam antenna where people are
  likely to be.

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Chapter 9 RF Exposure

• Use a lower gain antenna.
• Reduce your transmitter power.
• Limit or reduce the average power of your
  transmissions.
• Transmit for shorter periods
• Use a mode with a lower duty cycle

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Chapter 9 Mechanical Safety

• ALWAYS FOLLOW THE MANUFACTURERS DIRECTIONS!
• When installing a radio in your vehicle you want
  to preserve the safety you and your passengers
• Secure all equipment inside the vehicle
• If possible, use control heads (detachable
  front panels)
• Dont install the radio where it diverts your
  attention from driving or can block your view.
• Dont operate in heavy traffic
• Pull over to make complicated adjustment
• Know the traffic laws in your state

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Chapter 9 Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURERS
DIRECTIONS! Before you start installing a tower
or an antenna on your property, check with your
home owners association and also check any local
zoning codes to ensure that its OK. If your
tower exceeds 200 feet or youre near an airport
youll need to check with the FCC and the
FAA. Place all antennas and feed lines clear of
power lines including the service drop to your
home. Ensure you have at least 10 feet of
clearance beyond your mast or tower height from
the nearest power line.
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Chapter 9 Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURERS
DIRECTIONS! Never attach an antenna or guy wire
to a utility pole since a mechanical failure
could result in contact with high-voltage
wires. Follow your local electrical code when
grounding antennas and support systems. Towers
should be grounded with separate 8-foot long
ground rods for each tower leg, bonded to the
tower and to each other.
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Chapter 9 Mechanical Safety

• ALWAYS FOLLOW THE MANUFACTURERS DIRECTIONS!
• Most antennas work better when installed as high
  as is practical and that usually means installing
  a tower or some sort.
• When working on a tower or as part of the ground
  crew, safety is absolutely critical.
• Each member of the crew should wear hard hats,
  goggles or safety goggles, and heavy gloves.
• Use sun screen lotion

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Chapter 9 Mechanical Safety

• ALWAYS FOLLOW THE MANUFACTURERS DIRECTIONS!
• If youre the climber use an approved
  climbing harness DO NOT use a linemans belt
  and work boots to protect the arches of your
  feet.
• Inspect all tower guying and support hardware.
  Repair or tighten before you climb.
• Crank-up towers must be fully nested in the
  retracted position and blocked. Never climb a
  crank-up tower supported only by its support
  cable.

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Chapter 9 Mechanical Safety

• ALWAYS FOLLOW THE MANUFACTURERS DIRECTIONS!
• Double-check all climbing belts and lanyards.
  Make sure all clips and carabiners work smoothly
  and do not stick in the open or closed position.
• Make sure all ropes and load-bearing hardware
  are in good condition.
• Use a gin pole (a temporary mast that is
  attached to the tower) to hoist stuff (e.g.,
  tools, parts, tower sections, antenna, etc.) up
  the tower.

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Chapter 9 Mechanical Safety

• ALWAYS FOLLOW THE MANUFACTURERS DIRECTIONS!
• Double-check the latest weather reports.
• Visit the bathroom before you climb the tower.
  Your ground crew will thank you.
• Avoid climbing alone whenever possible because
  its never safe.
• Make sure all power to the tower is turned off.
• Stay clear of the base of the tower unless you
  need to be there and never remove your hard hat
  until the climber is on the ground.

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Chapter 9 Mechanical Safety
The End