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Electrical Safety

Electrical Safety.

jaden
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Electrical Safety

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  1. Electrical Safety • Amateur radios operated at high power produce dangerous and potentially deadly voltages and current. For example, it is commonly accepted that a voltages as low as 30 volts can cause a dangerous electric shock. It is very important to know how to work safely with electricity.

  2. Lethal Current • There is a saying in electronics that “It’s the volts that jolts, but the mills that kills.” • As little as 100 milliamperes of electrical current flowing through the human body is likely to cause death. That’s only .1 amp, and this kind of current is very common in radio equipment!

  3. Safe Wiring • You may find yourself installing or replacing an electrical outlet at some point. A typical modern outlet has three different wires, each with a different color. Each color must be connected correctly. Black wires go to the brass or gold terminals, white wires are connected to the silver terminals, and the bare or green wire is connected to the ground screw.

  4. Fuses • Fuses are extremely important safety devices. The purpose of a fuse in an electrical circuit is to interrupt power in case of overload. This may happen if something inside the device “shorts” causing too much current to flow. Fuses are usually rated by the amount of current that will cause them to open or “blow.” A 10 amp fuse will open if 10 or more amps flow through the circuit it protects. When it opens, power to the unit is cut off.

  5. Using the Right Size Fuse • You should always use a fuse of the correct size or rating. If you use a fuse rated for less current than that called for, the fuse will blow when the equipment is operating normally. If you use one that is rated for a higher current, it could cause enough current to flow through the device to do serious damage before the fuse opens. Worse yet, the heat generated could start a fire. For example, if you install a 20-ampere fuse in your transceiver in the place of a 5-ampere fuse, excessive current could cause a fire or burn up the transceiver circuitry.

  6. Ways to Prevent Electrical Shock • There are several good ways to guard against electrical shock at your station. They include: • Using 3-wire cords and plugs for all AC powered equipment • Connecting all AC powered station equipment to a common ground • Using a ground-fault interrupter at each electrical outlet

  7. Emergency Disconnect Switch • An emergency disconnect switch will quickly cut off all power to your station. This may be very important if something goes wrong while you are away from your operating position. For that reason, the most important thing to consider when installing an emergency disconnect switch at your station is that everyone should know where it is and how to use it. If others in your home don’t know where it is, they cannot turn it off in your absence.

  8. Lightning Storms • Lightning storms can be extremely dangerous, particularly to hams, because outdoor antennas make great lightning rods. If an antenna is hit by lightning, the electrical charge the lightning carries is headed straight for you and your station. When a lightning storm is expected, you should: • Disconnect the antenna cables from your station and move them away from your radio equipment • Unplug all power cords from AC outlets • Stop using your radio equipment and move to another room until the storm passes

  9. Lightning and Fire • Without a doubt, the most important reason to have a lightning protection system for your amateur radio station is fire prevention.

  10. Emergency Power • If you are able to use a 12 volt battery as a power source for your radio, one simple way to recharge the 12-volt battery if the commercial power is out is to connect the battery to a car's battery and run the engine.

  11. Battery Safety • Conventional 12-volt storage batteries are widely available and often used by hams as an emergency power source. However, they must be handled carefully due to the potential hazards they pose. Hazards presented by conventional 12-volt storage batteries include: • They contain dangerous acid that can spill and cause injury if the case is broken. • Short circuits can damage wiring and possibly cause a fire • Explosive gas produced by such batteries can collect if not properly vented

  12. Avoid Rapid Charge or Discharge of Storage Batteries • If a storage battery is charged or discharged too quickly, the battery could overheat and give off dangerous gas or explode. Most newer chargers are “smart” chargers that will prevent a too rapid charge. To prevent a battery from being discharged too quickly, you should use enough batteries in parallel to safely power your equipment.

  13. Capacitors • You will learn more about capacitors when you study for your General class license. For now, however, you need to know that some types of capacitors, such as the electrolytic capacitors shown here, are capable of storing an electrical charge of hundreds of volts, and they can remain charged long after power is turned off. Devices such as power supplies have large capacitors that can hold dangerous charges. Even when a power supply is turned off and disconnected, you might receive an electric shock from a stored charge in these capacitors if you don’t know what your are doing. It’s not on the exam, but you should learn how to safely discharge these capacitors.

  14. Check-Up Time! Now let’s try the questions from this group. You should make a note of any that you miss for later review.

  15. 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

  16. T0A01 Answer - B • Thirty volts can be dangerous, although you can still get a nasty shock at voltages lower than this.

  17. 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

  18. T0A02 Answer - B • 100 milliamperes or .1 amp is enough to kill. That doesn't sound like much, but bear in mind the old saying, "It's the volts that jolts, but the mils that kills!"

  19. T0A03 • What is connected to the green wire in a three-wire electrical plug? • A. Neutral • B. Hot • C. Ground • D. The white wire

  20. T0A03 Answer - C • For safety, the green wire should always be connected to the ground terminal.

  21. 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

  22. T0A04 Answer - B • If a circuit suddenly begins to draw too much power, usually due to a component failure, the fuse "blows" breaking the connection between the device and the power source. Circuit breakers do the same thing, but unlike fuses, they can be reset and do not have to be replaced.

  23. 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

  24. T0A05 Answer - C • Using a fuse larger than the value called for will allow more current to flow before it "blows." This could cause all kinds of damage, including allowing the transceiver to literally burn up, and could possibly start a fire as well.

  25. 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

  26. T0A06 Answer - D • All of these answers are good ways to protect yourself and your station from damage or injury. Hams often use equipment and components that develop high voltages and current. It is smart to play it safe!

  27. 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

  28. T0A07 Answer - C • An emergency disconnect allows you to "pull the plug" on all connected equipment instantly. Everyone in your home should know how to do this because you may not be around when it needs to be done.

  29. 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

  30. T0A08 Answer - D • All of these answers are correct. No good can come from a lightning bolt surging through your equipment. The easiest path for a lightning bolt to your radio is the outside antenna. Disconnect it. The next best path is through your home wiring, so you should always unplug your equipment and any other valuable appliances when a storm is approaching. Finally, if you are connected to your equipment when lightning strikes, need we say more?

  31. T0A09 • What is one way to recharge a 12-volt battery if the commercial power is out? • A. You cannot recharge a battery unless the power is back on • B. Add water to the battery • C. Connect the battery to a car's battery and run the engine • D. Take your battery to the utility company for a recharge

  32. T0A09 Answer - C • If your 12 volt battery is running low and the power is out, you can always recharge it using jumper cables from your car's battery.

  33. T0A10 • What kind of hazard is presented by a conventional 12-volt storage battery? • A. It contains dangerous acid that can spill and cause injury • B. Short circuits can damage wiring and possibly cause a fire • C. Explosive gas can collect if not properly vented • D. All of these answers are correct

  34. T0A10 Answer - D • All of these answers are correct. 12 volt batteries are great for emergency power, but they are somewhat dangerous. Dangers include acid spills, shorts, and unvented gasses.

  35. T0A11 • What can happen if a storage battery is charged or discharged too quickly? • A. The battery could overheat and give off dangerous gas or explode • B. The terminal voltage will oscillate rapidly • C. The warranty will be voided • D. The voltage will be reversed

  36. T0A11 Answer - A • Charging or discharging a battery too quickly can cause overheating and possibly dangerous gas that could lead to an explosion. There are all kinds of "smart chargers" on the market today that will help you to avoid this very unpleasant result.

  37. T0A12 • What is the most important reason to have a lightning protection system for your amateur radio station? • A. Lower insurance rates • B. Improved reception • C. Fire prevention • D. Noise reduction

  38. T0A12 Answer - C • Nothing is more important than fire prevention. It doesn't matter how good your insurance happens to be. Some things simply cannot be replaced!

  39. 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

  40. T0A13 Answer - D • Power supplies rely on capacitors to produce smooth direct current at a steady voltage. These capacitors can store a hefty charge long after the supply has been turned off. Touching the leads of a charged capacitor can be very dangerous.

  41. Group T0B Group T0B covers antenna installation, tower safety, and overhead power lines.

  42. Antenna Safety • Antenna safety goes hand in hand with electrical safety. Installing and maintaining an antenna can be dangerous if you don’t play it safe. For example, you should wear a hard hat and safety glasses if you are on the ground helping someone work on an antenna tower to protect your head and eyes in case something accidentally falls from the tower.

  43. Climbing Safety • Another good idea before climbing an antenna tower is to put on a good climbing safety belt and safety glasses. One slip and it’s a long way down to the ground! In addition, you should arrange for a helper or observer on the ground, inspect the tower for damage or loose hardware, and above all, make sure there are no electrical storms nearby.

  44. Picking a Site for Your Antenna • When you are transmitting, antennas can carry large high currents, so one very important consideration when putting up an antenna is to make sure people cannot accidentally come into contact with it. You don’t want someone getting a dangerous shock or RF burn.

  45. Antennas and Airports • If you live close to an airport, you need to consult Part 97 to see whether you are close enough for height restrictions to be imposed on your antenna. (See § 97.15(A))

  46. Keep Antennas Away From Power Lines! • The absolute most important safety precaution to observe when putting up an antenna tower is to look for and stay clear of any overhead electrical wires. If a falling antenna hits power lines, it can bring dangerous and damaging voltages into your station and could cause death by electrocution.

  47. Safe Distance from Power Lines • A good rule of thumb for maintaining a safe distance to from a power line when installing an antenna is to install the antenna so that if it falls unexpectedly, no part of it can come closer than 10 feet to the power wires. That is an absolute minimum. Any less than that, and you are asking for trouble.

  48. Tower Guy Wires • Most towers of any size need to have guy wires in place to secure the tower during high winds. The guy wires for an antenna tower should be installed strictly in accordance with the tower manufacturer's instructions. The engineers who designed the tower are in the best position to know how it should be done.

  49. Crank-up Towers • Crank-up towers are towers made of nested sections that can be raised or lowered by means of a hand crank or electrical motor. However, these nested sections can fall, so the most important safety rule to remember when using a crank-up tower is that a crank-up tower should never be climbed unless it is in the fully lowered position. If you are on a higher section that gives way, you not only run the risk of falling. You may also run a very real risk of having a limb severed.

  50. Preventing Antenna Corrosion • Stainless steel hardware is used on many antennas instead of other cheaper metals because stainless steel parts are much less likely to corrode than the cheap stuff. Corrosion not only damages the antennas. It also seriously affects your signal.

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