G-10

G-10

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SUBELEMENT G0 – ELECTRICAL AND RF SAFETY

[2 Exam Questions – 2 Groups]

G0A – RF safety principles, rules and guidelines; routine station evaluation

Its duty cycle, frequency and power density are important in estimating whether an RF signal exceeds the maximum permissible exposure (MPE). You can determine that your station complies with FCC RF exposure regulations by calculations based on FCC OET Bulletin 65, calculations based on computer modeling and measurement of field strength using calibrated equipment. “Time averaging” means the total RF exposure averaged over a certain time in reference to RF radiation exposure. If an evaluation of your station shows RF energy radiated from your station exceeds permissible limits take action to prevent human exposure to the excessive RF fields. A lower transmitter duty cycle permits greater short-term exposure levels when evaluating RF exposure. An amateur operator must perform a routine RF exposure evaluation to ensure compliance with RF safety regulations when transmitter power exceeds levels specified in FCC Part 97.13. Make sure that MPE limits are not exceeded in occupied areas when you install an indoor transmitting antenna.

Heating body tissue is one way that RF energy can affect human body tissue. Turn off the transmitter and disconnect the feed line whenever you make adjustments or repairs to an antenna. A ground-mounted antenna should be installed so it is protected against unauthorized access. A calibrated field strength meter with a calibrated antenna can be used to accurately measure an RF field. Take precautions to ensure that the antenna cannot be pointed in their direction is one thing that can be done if evaluation shows that a neighbor might receive more than the allowable limit of RF exposure from the main lobe of a directional antenna.

G0B – Safety in the ham shack: electrical shock and treatment, safety grounding, fusing, interlocks, wiring, antenna and tower safety

Only the two wires carrying voltage in a four-conductor connection should be attached to fuses or circuit breakers in a device operated from a 240 VAC single phase source.

AWG number 12 is the minimum wire size that may be safely used for a circuit that draws up to 20 amperes of continuous current. 15 amperes fuse or circuit breaker would be appropriate to use with a circuit that uses AWG number 14 wiring. Current flowing from one or more of the voltage-carrying wires directly to ground will cause a Ground Fault Circuit Interrupter (GFCI) to disconnect the 120 or 240 Volt AC line power to a device. Danger of carbon monoxide poisoning is a primary reason for not placing a gasoline-fueled generator inside an occupied area. Metal enclosure of every item of station equipment must be grounded to ensure that hazardous voltages cannot appear on the chassis.

These choices should be observed when climbing a tower using a safety belt or harness, confirm that the belt is rated for the weight of the climber and that it is within its allowable service life. Make sure all circuits that supply power to the tower are locked out and tagged before any person preparing to climb a tower that supports electrically powered devices. Soldered joints should not be used with the wires that connect the base of a tower to a system of ground rods because it will likely be destroyed by the heat of a lightning strike.

Bonding them together with all other grounds is good practice for lightning protection grounds. To ensure that dangerous voltages are removed if the cabinet is opened is the purpose of a power supply interlock. Disconnect the incoming utility power feed when you are powering your house from an emergency generator. Electrical safety inside the ham shack is covered by the National Electrical Code. An emergency generator should be located in a well-ventilated area.

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