G0 Electrical and RF Safety

A. It heats body tissue

RF energy absorbed by the body is converted to heat, raising tissue temperature. This heating is the main biological effect of RF and the basis of the FCC exposure limits; RF is non-ionizing, so it does not cause the damage associated with ionizing radiation.

• B. Radiation poisoning (radiation sickness) is caused by ionizing radiation such as gamma rays; RF is non-ionizing.
• C. A dangerously low blood count is an effect of large doses of ionizing radiation, not RF.
• D. Absorbed RF energy adds heat to tissue; it does not cool it.

D. All these choices are correct

RF exposure depends on how strong the field is where people are (its power density), how readily the body absorbs that frequency, and how much of the time the transmitter is on. The maximum permissible exposure limits in 47 CFR 1.1310 are power densities that vary with frequency and are averaged over time.

• A. True: duty cycle sets the average power, and exposure limits are averaged over time, but it is only one of the factors.
• B. True: the body absorbs RF differently at different frequencies, so the limits vary with frequency (they are lowest from 30 to 300 MHz), but frequency is only one of the factors.
• C. True: power density, in mW/cm², is the quantity compared with the exposure limits, but it is only one of the factors.

D. All these choices are correct

Under 47 CFR 97.13(c)(1), the licensee must ensure the station complies with the FCC RF exposure rules, and OET Bulletin 65, Supplement B, describes methods for amateur stations. A station can be evaluated by calculation, by computer modeling of the antenna, or by measuring field strength with calibrated equipment.

• A. True: OET Bulletin 65 gives formulas and tables for calculating exposure, but calculation is only one of the accepted methods.
• B. True: antenna modeling software can compute the field strength around an antenna, but modeling is only one of the accepted methods.
• C. True: measuring field strength with calibrated equipment shows actual exposure levels, but measurement is only one of the accepted methods.

Pool citation: 97.13(c)(1)

D. The total RF exposure averaged over a certain period

RF exposure limits apply to the exposure averaged over a set period, not to each instant. Under 47 CFR 1.1310, the averaging time is up to 6 minutes for occupational/controlled exposure and up to 30 minutes for general population/uncontrolled exposure, so brief exposure above the limit is allowed if the average stays within it.

• A. Time averaging applies to exposure over 6 or 30 minutes, not to transmitter power over a 24-hour period.
• B. Time averaging is a method of evaluating exposure, not a measure of how long RF takes to cause effects.
• C. Total exposure time alone is not an average; time averaging spreads the total exposure over the averaging period.

A. Take action to prevent human exposure to the excessive RF fields

Under 47 CFR 97.13(c)(2), if the routine evaluation shows that RF fields could exceed the limits of 47 CFR 1.1310 in accessible areas, the licensee must take action to prevent human exposure. Options include reducing power, moving or raising the antenna, or keeping people out of the affected area.

• B. There is no "EIS-97" filing; the rule requires the licensee to prevent exposure to the excessive fields.
• C. Neighbors cannot authorize exposure above the limits; people outside the licensee's household must be protected to the general population limits under 47 CFR 97.13(c)(1).
• D. Filing an "EIS-97" and getting written permission from neighbors are not valid responses, so not all the choices are correct.

Pool citation: 97.13(c)(2), 1.1307(b)

A. Perform an RF exposure evaluation in accordance with FCC OET Bulletin 65

A station that does not qualify for an exemption under 47 CFR 1.1307(b)(3) must be evaluated for RF exposure. 47 CFR 97.13(c)(1) points amateurs to FCC OET Bulletin 65, Supplement B, for evaluation methods.

• B. No FCC permission is needed; the licensee performs the evaluation and makes sure the limits are met.
• C. The World Meteorological Organization deals with weather and climate, not RF exposure; FCC evaluations follow OET Bulletin 65.
• D. A band-pass filter removes unwanted emissions but does not reduce exposure from the intended signal, and no such filter is required for RF exposure compliance.

Pool citation: 97.13(c)(2), 1.1307(1)(b)(3)(i)

A. A lower duty cycle permits greater power levels to be transmitted

Exposure limits are averaged over time (47 CFR 1.1310). A mode with a low duty cycle, such as CW or SSB voice, produces less average power for a given peak power than a high-duty-cycle mode such as FM or FT8, so more power can be used before reaching the same average exposure.

• B. A higher duty cycle raises the average exposure, so it permits less power, not more.
• C. No rule exempts low-duty-cycle transmitters; duty cycle only lowers the time-averaged power used in the exemption test and evaluation (47 CFR 1.1307(b)).
• D. High-duty-cycle transmitters produce more average exposure, and nothing exempts them from the RF exposure rules.

C. Perform a routine RF exposure evaluation and prevent access to any identified high exposure areas

Under 47 CFR 97.13(c), the licensee must ensure compliance with the RF exposure rules through a routine evaluation and, if fields could exceed the limits in accessible areas, must prevent people from being exposed, for example by keeping them out of the high-exposure areas.

• A. No rule requires posting a copy of 47 CFR 97.13 in the station.
• B. No rule requires notifying neighbors of the station or its power levels.
• D. Posting the rule and notifying neighbors are not required, so not all the choices are correct.

Pool citation: 97.13(c)(2)

B. A calibrated field strength meter with a calibrated antenna

Accurate field strength measurement needs an instrument whose readings are traceable to a known standard: a calibrated field strength meter used with a calibrated antenna (probe). Uncalibrated equipment can show relative changes but not true field strength.

• A. A receiver shows relative signal strength, not calibrated field strength, and DSP noise reduction alters what it displays.
• C. An SWR meter measures forward and reflected power in the feed line, not the field in the space around the antenna.
• D. An oscilloscope displays waveforms, and a crystal marker generator provides frequency reference points; neither measures field strength.

C. Take precautions to ensure that the antenna cannot be pointed in their direction when they are present

The main lobe of a directional antenna carries its strongest field. If a neighbor could be exposed above the limit in that lobe, the station must make sure the antenna cannot point at them while they are present, for example by limiting the rotator's range or reducing power.

• A. Every antenna has a polarization, and switching to a higher-gain antenna would increase the field in the main lobe, making the problem worse.
• B. A higher front-to-back ratio reduces radiation to the rear of the antenna, but the problem here is in the main lobe.
• D. A higher-gain antenna or a better front-to-back ratio does not fix exposure in the main lobe, so not all the choices are correct.

C. Make sure that MPE limits are not exceeded in occupied areas

An indoor antenna puts the radiating element close to where people live and work, so fields in occupied rooms can be strong. The station must be evaluated to make sure the maximum permissible exposure (MPE) limits are not exceeded in those areas.

• A. Placing the antenna close to the operating position increases the operator's exposure rather than reducing it.
• B. Running an antenna along the edge of a wall does not control RF exposure, and "parasitic radiation" is not the safety concern.
• D. Shielding an antenna would stop it from radiating, which defeats its purpose; the requirement is to keep exposure in occupied areas within the limits.

D. All stations with a time-averaged transmission of more than one milliwatt

Under 47 CFR 1.1307(b)(3)(i)(A), an RF source whose available maximum time-averaged power is no more than 1 mW is exempt from routine evaluation regardless of distance. Any station above that level must qualify for another exemption or be evaluated, and amateur stations are included (47 CFR 97.13(c)).

• A. Amateur stations are not exempt; 47 CFR 97.13(c) requires amateur licensees to comply with the RF exposure rules.
• B. There is no cutoff based on antenna height; height affects exposure, but every station above 1 mW time-averaged power is subject to the rules.
• C. The current rules have no 500 W threshold; whether a station is exempt depends on its power, frequency and distance to people (47 CFR 1.1307(b)(3)).

Pool citation: 1.1307(1)(b)(3)(i)(A)

A. Only the hot wires

Fuses and circuit breakers go only in the hot (ungrounded) conductors. A four-wire 240 VAC circuit has two hot wires, a neutral and a ground, and opening the neutral or ground could leave equipment energized through the hot wires while removing its return or safety path.

• B. A fuse in the neutral could open while the hot wires remain live, leaving equipment energized even though it appears dead.
• C. The ground wire is the safety path for fault current and must never be interrupted.
• D. Fusing every wire would interrupt the neutral and ground, which must stay continuous; only the hot wires are fused.

C. AWG number 12

The National Electrical Code requires copper wire of at least AWG 12 on a circuit protected by a 20-ampere breaker (AWG 14 is limited to 15 A). Smaller AWG numbers mean thicker wire, which carries more current safely.

• A. AWG 20 is much thinner than AWG 12 (higher numbers are thinner wire) and would overheat at 20 A.
• B. AWG 16 is thinner than AWG 12 and is not permitted for a 20 A circuit.
• D. AWG 8 is much thicker than needed for 20 A; it is safe but is not the minimum size.

D. 15 amperes

Under the National Electrical Code, AWG 14 copper wiring is protected by a fuse or breaker of no more than 15 amperes. The overcurrent device must trip before the current heats the wire to an unsafe temperature.

• A. A 30 A circuit requires AWG 10 wire; AWG 14 would overheat before the protection tripped.
• B. 25 A is more current than AWG 14 wiring may carry, so the wire would not be protected.
• C. A 20 A circuit requires AWG 12 wire; AWG 14 is limited to 15 A.

B. Outside the building

The lightning protection ground belongs outside the building, so a strike on the antenna or feed line is carried into the earth before it can enter the house. It is bonded to the building's electrical service ground.

• A. Placing the lightning ground next to the equipment would bring lightning current inside the building.
• C. The ground at a utility pole belongs to the power company; the station lightning ground is at the building, bonded to its service ground.
• D. Running the ground parallel to the water supply line is not a requirement; what matters is that it is outside and bonded to the other grounds.

B. Current flowing from one or more of the hot wires directly to ground

A GFCI compares the current in the hot and neutral wires. Normally they are equal, but if a few milliamperes leak from a hot wire directly to ground, for example through a person, the imbalance trips the GFCI.

• A. Current from hot to neutral is normal load current and stays balanced, so it does not trip a GFCI; overcurrent is handled by the breaker or fuse.
• C. A GFCI senses current imbalance, not voltage, so overvoltage does not trip it.
• D. Normal hot-to-neutral current and overvoltage do not trip a GFCI, so not all the choices are correct.

C. Electrical safety of the station

The National Electrical Code is the US standard for safe electrical wiring and installation, including conductor sizes, fusing and grounding, and it applies to the wiring of an amateur station.

• A. Transmitted bandwidth limits come from FCC rules (47 CFR Part 97), not the electrical code.
• B. Modulation limits come from FCC rules, not the electrical code.
• D. RF exposure limits for the human body come from FCC rules (47 CFR 1.1310), not the electrical code.

B. Confirm that the harness is rated for the weight of the climber and that it is within its allowable service life

A safety harness protects a climber only if it is rated for the climber's weight and is in good condition. Harnesses have a limited service life set by the manufacturer, so check the rating and the age and condition before climbing.

• A. Climbers need both hands to climb and work; safety comes from staying attached to the tower with the harness lanyard, not from a one-hand rule.
• C. Heavy tools are raised and lowered with a rope rather than hung from the harness, where they add weight and can fall on people below.
• D. Holding on with one hand and hanging heavy tools on the harness are not correct practices, so not all the choices are correct.

B. Make sure all circuits that supply power to the tower are locked out and tagged

A tower may carry powered devices such as rotators, lights and preamplifiers. Before climbing, turn off every circuit feeding the tower and lock out and tag the switches or breakers, so no one can turn the power back on while someone is on the tower.

• A. The electric company does not control the circuits on your own wiring, and notifying it does not remove power from the tower.
• C. The tower ground protects against lightning and electrical faults and should never be removed.
• D. Notifying the power company and removing the ground do not make the tower safe, so not all the choices are correct.

A. The generator should be operated in a well-ventilated area

Engine-driven generators produce carbon monoxide, an odorless and deadly gas. A generator must run in a well-ventilated area outdoors, away from windows and doors where exhaust could enter a building.

• B. Nothing requires insulating a generator from ground; its frame is bonded or grounded according to the manufacturer's instructions and the electrical code.
• C. Fuel stored near a hot, running generator is a fire hazard; fuel should be stored away from it.
• D. Insulating the generator from ground and storing fuel next to it are wrong, so not all the choices are correct.

A. Lead can contaminate food if hands are not washed carefully after handling the solder

Lead is toxic, and handling lead-tin solder leaves lead on your hands. Wash your hands after soldering, before eating, so lead does not get into food.

• B. High voltage does not make solder disintegrate; the hazard of lead-tin solder is lead exposure.
• C. Tin "cold flowing" into shorts is not a hazard of lead-tin solder; the hazard is lead exposure.
• D. RF energy does not convert lead into a gas.

D. They must be bonded together with all other grounds

All grounds at the station, including lightning ground rods and the electrical service ground, must be bonded together. Bonding keeps them at the same potential during a strike, which prevents dangerous voltage differences and arcing between separate ground systems.

• A. Lightning ground rods are bonded to the building's grounding electrode system, not to every buried line; buried gas piping must never be used as a grounding electrode.
• B. Sharp bends raise the impedance of a ground wire to the fast lightning pulse; ground wires should run as straight as possible, with gentle bends.
• C. Connecting a ground to ungrounded (hot) wiring would create a short circuit.

C. To ensure that dangerous voltages are removed if the cabinet is opened

A power supply interlock is a switch that removes dangerous voltages, typically by disconnecting power, when the cabinet is opened. It protects anyone who opens the enclosure from the high voltages inside.

• A. An interlock is a safety device, not a way to protect the manufacturer's warranty.
• B. Shutting down when too hot is the job of thermal (overtemperature) protection, not an interlock.
• D. Shutting down on excess output voltage is the job of overvoltage protection, such as a crowbar circuit, not an interlock.

A. Where the feed lines enter the building

Lightning arrestors belong where the feed lines enter the building, usually on a grounded entry panel bonded to the station ground system. There they divert surges on the feed line to ground before they can reach the equipment inside.

• B. An arrestor on the antenna would not stop surges traveling along the feed line into the building.
• C. An arrestor connects between the feed line and ground; placed in series with a ground lead, it would block the path it is meant to provide.
• D. The power pole ground belongs to the utility; feed line arrestors go at the building entrance, bonded to the station ground.