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Subelement T0

SAFETY

Section T0B

Antenna safety: tower safety and grounding, installing antennas, antenna supports

Which of the following is good practice when installing ground wires on a tower for lightning protection?

  • Put a drip loop in the ground connection to prevent water damage to the ground system
  • Make sure all ground wire bends are right angles
  • Correct Answer
    Ensure that connections are short and direct
  • All these choices are correct

Use large wires over short distances on a direct path to the grounding rods - Lightning is high voltage, high current electricity, short and direct paths will lessen the chance of electricity to jump to nearby conductors.

The answers of using loops and right angles are the opposite of using short and direct connections. Lightning is high voltage, high current electricity.

Bends in the wire may allow the electricity to 'jump' from the wire to nearby conductors, thereby defeating the grounding system.

The longer the wires are, the more resistance there is and the hotter the wire will get.

Once again: Use large wires over short distances on a direct path to the grounding rods - short and direct.

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Tags: grounding safety section5.5

What is required when climbing an antenna tower?

  • Have sufficient training on safe tower climbing techniques
  • Use appropriate tie-off to the tower at all times
  • Always wear an approved climbing harness
  • Correct Answer
    All these choices are correct

This question is entirely basic safety steps. Remember, we are trying to save lives, not risk them. An antenna tower cannot retract like a crank tower.

It is always the safest to have both certification and experience climbing before moving to climb an antenna tower.

Using an appropriate tie-off prevents you from falling off of the tower, so this is required.

If you don’t use an approved harness, it may break and cause you to fall, harming or killing you.

So, all of these choices are correct.

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Tags: section5.5

Under what circumstances is it safe to climb a tower without a helper or observer?

  • When no electrical work is being performed
  • When no mechanical work is being performed
  • When the work being done is not more than 20 feet above the ground
  • Correct Answer
    Never

Always take the time to get someone to help. Never climb a tower without someone else to help or observe.

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Tags: safety section5.5

Which of the following is an important safety precaution to observe when putting up an antenna tower?

  • Wear a ground strap connected to your wrist at all times
  • Insulate the base of the tower to avoid lightning strikes
  • Correct Answer
    Look for and stay clear of any overhead electrical wires
  • All these choices are correct

These two answers are clearly incorrect. A grounded wrist strap is for use on electronics and won't help when working on a tower. Insulating the base won't stop lightning strikes and eliminates the grounding system that protects the tower. The only answer that is an important safety precaution is to look for and stay clear of overhead electrical wires. The tower, guy wires and you should be well clear of any overhead electrical wires. Refer to question B06 for more information on safe distances.

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Tags: safety towers section5.5

What is the purpose of a safety wire through a turnbuckle used to tension guy lines?

  • Secure the guy line if the turnbuckle breaks
  • Correct Answer
    Prevent loosening of the turnbuckle from vibration
  • Provide a ground path for lightning strikes
  • Provide an ability to measure for proper tensioning

You tighten turnbuckles by turning them, but with vibration, they can come loose. The safety wire keeps them from turning, once they're tight.

They won't help if the turnbuckle breaks - they're too fragile.

They won't prevent theft or vandalism because they're easily removed.

They have nothing to do with climbing the tower, because they're just used on the turnbuckles.

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Tags: section5.5

What is the minimum safe distance from a power line to allow when installing an antenna?

  • Add the height of the antenna to the height of the power line and multiply by a factor of 1.5
  • The height of the power line above ground
  • 1/2 wavelength at the operating frequency
  • Correct Answer
    Enough so that if the antenna falls, no part of it can come closer than 10 feet to the power wires

None of the other three answers provide any indication of how close the antenna will be to the power line if it falls. Note that this is the minimum and should only be used when necessary. It is better to create more distance than the 10 foot minimum whenever practical.

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Tags: safety section5.5

Which of the following is an important safety rule to remember when using a crank-up tower?

  • This type of tower must never be painted
  • This type of tower must never be grounded
  • Correct Answer
    This type of tower must not be climbed unless it is retracted, or mechanical safety locking devices have been installed
  • All these choices are correct

Obviously, the tower must be grounded. Clearly, the important safety precaution is to not climb the tower unless fully retracted. Climbing the tower requires that your hands and feet are placed between the parts of the tower that slide adjacent to each other. You can think of the tower as a possible guillotine that can severely injure and even remove body parts that are in the way if it accidentally slips. Even when retracted, it is a good idea to block the tower to prevent the sections from moving.

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Tags: safety towers section5.5

Which is a proper grounding method for a tower?

  • A single four-foot ground rod, driven into the ground no more than 12 inches from the base
  • A ferrite-core RF choke connected between the tower and ground
  • A connection between the tower base and a cold water pipe
  • Correct Answer
    Separate eight-foot ground rods for each tower leg, bonded to the tower and each other

The general idea of grounding a tower is to provide a short, direct path for high voltage/current lightning strikes to ground. If a single ground rod is used, it increases the distance required and drops the efficiency of the grounding system. A single four-foot grounding rod is not adequate to handle typical electrical energy generated in a lightning strike. Clearly, the ferrite-core RF choke is of no use, as it is used in electronic circuits. In addition to that, connecting the tower to a cold water pipe poses a serious safety concern for people who might be near the plumbing in the house the water pipe connects to. The best answer is long (8-10ft) grounding rods, one for each tower leg, that are bonded to the tower and to each other.

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Tags: grounding safety towers section5.5

Why should you avoid attaching an antenna to a utility pole?

  • The antenna will not work properly because of induced voltages
  • The 60 Hz radiations from the feed line may increase the SWR
  • Correct Answer
    The antenna could contact high-voltage power lines
  • All these choices are correct

It should be pretty obvious that any antenna should be far away from power lines, both to avoid accidental contact and to avoid interference. Also consider that installing and maintaining the antenna exposes you to the risk of accidental contact with the power wires as well.

The all are correct answer, however, is false. First the answer about 60Hz radiations affecting the SWR says they are coming from the feed line, when they actually would be coming from the power lines. Second, induced currents in the antenna might damage the transceiver if they were strong enough, or be received as static or unwanted noise (aka, interference) if they were at the right frequency, but this does not mean the antenna would be malfunctioning per se: The antenna would actually be functioning exactly as intended, turning radio waves into electricity.

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Tags: safety antenna section5.5

Which of the following is true when installing grounding conductors used for lightning protection?

  • Use only non-insulated wire
  • Wires must be carefully routed with precise right-angle bends
  • Correct Answer
    Sharp bends must be avoided
  • Common grounds must be avoided

Sharp bends, which includes right angles, must be avoided. While non-insulated wire is generally used for grounding, it is not required. For example, metal straps may be used instead of wires, but you won't see this commonly. Common grounds are recommended. The best grounding system uses conductors that are as short and straight as possible.

"Short and Direct"

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Tags: safety grounding section5.5

Which of the following establishes grounding requirements for an amateur radio tower or antenna?

  • FCC Part 97 rules
  • Correct Answer
    Local electrical codes
  • FAA tower lighting regulations
  • UL recommended practices

Because the grounding system falls under an electrical installation, it is governed by local electrical codes. Most local codes are based on the National Electrical Code (NEC), so in most cases they will just refer you to the NEC. You should be aware that local codes vary dramatically throughout the United States in terms of who can inspect and approve electrical installations, so it's always a good idea to check with your local code enforcement office to find out what the requirements are.

In Article 100 of the NEC, the local electric codes are governed by the term Authority Having Jurisdiction (AHJ), which is defined as “An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure.” Grounding requirements would fall under their jurisdiction.

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Tags: rules and regulations grounding towers antenna section5.5

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