1. Chapter 9
Safety

2. 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.
A little common sense goes a long way.
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3. Chapter 9 Electrical Safety
Electrical Injuries
Electrical hazards produce two types of injury:
Shocks
Burns
Whenever electricity flows through any part of your body both can occur (AC or DC).
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4. Effects of Electric Current in the Human Body (table 9-1, pg 9-2)
Chapter 9
Electrical Safety
Electrical Injuries
Effects of Electric Current in the Human Body (table 9-1, pg 9-2)
Current
Reaction
Below 1 milliampere
Generally not perceptible
1 milliampere
Faint tingle
5 milliamperes
Slight shock; not painful but disturbing, Involuntary reaction
6-25 milliamperes (Women)
9-30 milliamperes (Men)
Painful shock, loss of muscular control; “can’t let go” range.
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5. 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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6. 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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7. 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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8. Chapter 9 Electrical Safety
Response to Electrical Injury
If you or someone receives an electrical shock…
Turn off the power – don’t 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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9. Chapter 9 Electrical Safety
AC Safety Grounding
Most ham stations DO NOT require new wiring and can operate safely when powered from your home’s 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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10. Chapter 9 Electrical Safety
AC Safety Grounding
NEVER replace a fuse or circuit breaker with one of a larger size. (table 9-2, pg. 9-4)
Don’t 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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11. Chapter 9 Electrical Safety
AC Safety Grounding
Use cable and wire sufficiently rated for the expected current load. (table 9-2, pg 9-4)
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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12. 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 (#8 copper wire to 8’ copper-clad ground rod of 5/8” diameter).
Ground connections should be as short as possible and avoid sharp bends.
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13. 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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14. 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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15. Chapter 9
RF Exposure
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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16. 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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17. 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 adult’s head is resonant at about 400 MHz).
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18. Chapter 9
RF Exposure
In a “controlled” environment people are aware of the their exposure and can take the necessary steps to minimize it:
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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19. Chapter 9
RF Exposure
People in “uncontrolled” environments are not aware of their exposure – areas open to the general public and your neighbor’s property – and their risk of exposure is generally less than in “controlled” environments.
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20. 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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21. Chapter 9
RF Exposure
Duty cycle is the ratio of the transmitted signal’s on-the-air time to the total operating time during the measurement period. The maximum is 100% (Duty Cycle: Table 9-4, pg. 9-14)
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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22. 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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23. Chapter 9
RF Exposure
With the exception of mobile and hand held transceivers, the FCC requires all fixed stations be evaluated for RF exposure.
Most evaluations use the techniques outlined in the FCC’s 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.
The use of computer modeling is acceptable.
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24. Chapter 9
RF Exposure
Once you’ve 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). You’ll 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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25. Power Thresholds for RF Exposure Evaluation
Chapter 9
RF Exposure
Power Thresholds for RF Exposure Evaluation
Band
Watts
160 m
500
15 m
100
70 cm 70
80 m
12 m 75
33 cm
150
40 m
10 m 50
23 cm
200
30 m
425
6 m
13 cm
250
20 m
225
2 m
SHF (all bands)
17 m
125
1.25 m
If you need to do an evaluation, you can use on-line exposure calculators and pre-calculated tables. You’ll need to know the frequency and power level, distance from the antenna and the antenna’s radiation pattern.
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26. So what do you do if you find a potential hazard?
Chapter 9
RF Exposure
So what do you do if you find a potential hazard?
Locate antennas away from where people can get close to them – you don’t 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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27. Chapter 9 RF Exposure Use a lower gain antenna.
Reduce your transmitter power.
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28. ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Chapter 9
Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
When installing a radio in your vehicle you want to preserve the safety you and your passengers:
Secure all equipment inside the vehicle
Use “control heads” (detachable front panels)
Don’t install the radio where it diverts your attention from driving or can block your view.
Don’t operate in heavy traffic
Pull over to make complicated adjustment
Know the traffic laws in your state
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29. ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Chapter 9
Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Before you start installing a tower or an antenna on your property, check with your home owner’s association and also check any local zoning codes to ensure that it’s OK.
If your tower exceeds 200 feet or you’re near an airport you’ll 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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30. ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Chapter 9
Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURER’S 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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31. ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Chapter 9
Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURER’S 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 glasses, and heavy gloves.
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32. ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Chapter 9
Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
If you’re the “climber” use an approved climbing harness – DO NOT use a “lineman’s 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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33. ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Chapter 9
Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURER’S 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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34. ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Chapter 9
Mechanical Safety
ALWAYS FOLLOW THE MANUFACTURER’S DIRECTIONS!
Double-check the latest weather reports.
Avoid climbing alone whenever possible because it’s 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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35. The End Practice Tests!!!! Homework Chapter 9 Mechanical Safety
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