What is one way that RF energy can affect human body tissue?
AnswerIt heats body tissue
RF energy can be absorbed by the body and converted to heat. RF safety limits are intended in part to prevent excessive tissue heating.
RF PREP // FCC AMATEUR RADIO
G0 · Electrical and RF Safety
General · correct answers only, in question-pool order.
Which transmission characteristic related to transmit-on time is used to determine RF exposure?
AnswerDuty cycle.
Duty cycle describes the fraction of time the transmitter is actually transmitting during the exposure period. It is one of the factors used to determine RF exposure.
Which signal characteristic measured in hertz is used to determine RF exposure?
AnswerFrequency.
RF exposure limits vary with frequency, so operating frequency is one of the factors used when evaluating exposure from a transmitted signal.
Which field quantity is used to determine RF exposure from a transmitted signal?
AnswerPower density.
Power density expresses RF power distributed over an area and is one of the quantities used in evaluating RF exposure.
Which FCC publication can be used as the basis for calculating RF exposure compliance?
AnswerFCC OET Bulletin 65.
The question pool identifies calculation based on FCC OET Bulletin 65 as one accepted way to determine that a station complies with RF exposure regulations.
What modeling method can be used to determine RF exposure compliance?
AnswerComputer modeling.
The question pool identifies calculation based on computer modeling as an accepted method for determining RF exposure compliance.
What measurement method can be used to determine RF exposure compliance?
AnswerMeasurement of field strength using calibrated equipment.
Direct field-strength measurement with calibrated equipment is one accepted way to determine whether a station complies with RF exposure regulations.
What does “time averaging” mean when evaluating RF radiation exposure?
AnswerThe total RF exposure averaged over a certain period
Time averaging evaluates the total RF exposure over a defined period rather than treating every instant as though the transmitter were continuously at peak output.
What must you do if an evaluation of your station shows that the RF energy radiated by your station exceeds permissible limits for possible human absorption?
AnswerTake action to prevent human exposure to the excessive RF fields
If an RF evaluation shows exposure above the permissible limit, the station must be operated or arranged so people are not exposed to those excessive fields.
What must you do if your station fails to meet the FCC RF exposure exemption criteria?
AnswerPerform an RF exposure evaluation in accordance with FCC OET Bulletin 65
Failing the FCC exemption criteria means the station cannot simply assume compliance. An RF exposure evaluation must be performed using the FCC guidance in OET Bulletin 65.
What is the effect of modulation duty cycle on RF exposure?
AnswerA lower duty cycle permits greater power levels to be transmitted
A lower duty cycle means the transmitter is on for a smaller fraction of the averaging period. That can allow a higher transmitter power while keeping time-averaged exposure within limits.
Which of the following steps must an amateur operator take to ensure compliance with RF safety regulations?
AnswerPerform a routine RF exposure evaluation and prevent access to any identified high exposure areas
Compliance requires evaluating RF exposure and then controlling access to any area where the evaluation identifies excessive exposure.
What type of instrument can be used to accurately measure an RF field strength?
AnswerA calibrated field strength meter with a calibrated antenna
Accurate RF field measurements require an instrument and antenna with known calibration so the indicated field strength can be related to the actual field.
What should be done if evaluation shows that a neighbor might experience more than the allowable limit of RF exposure from the main lobe of a directional antenna?
AnswerTake precautions to ensure that the antenna cannot be pointed in their direction when they are present
A directional antenna concentrates RF in its main lobe. If that lobe could expose a neighbor above the allowable limit, operating precautions must prevent the antenna from being pointed toward them while they are present.
What precaution should be taken if you install an indoor transmitting antenna?
AnswerMake sure that MPE limits are not exceeded in occupied areas
An indoor transmitting antenna places people much closer to the radiating structure, so the installation must be arranged so occupied areas remain within the maximum permissible exposure limits.
What stations are subject to the FCC rules on RF exposure?
AnswerAll stations with a time-averaged transmission of more than one milliwatt
The pool states that FCC RF-exposure rules apply to stations with time-averaged transmissions greater than one milliwatt.
Which wire or wires in a four-conductor 240 VAC circuit should be attached to fuses or circuit breakers?
AnswerOnly the hot wires
Overcurrent protection belongs in the ungrounded hot conductors. The neutral and safety-ground conductors are not normally fused in a four-conductor 240 VAC circuit.
According to the National Electrical Code, what is the minimum wire size that may be used safely for wiring with a 20-ampere circuit breaker?
AnswerAWG number 12
The question pool pairs a 20-ampere circuit breaker with a minimum conductor size of AWG 12 under the National Electrical Code.
Which size of fuse or circuit breaker would be appropriate to use with a circuit that uses AWG number 14 wiring?
Answer15 amperes
The question pool specifies a 15-ampere fuse or circuit breaker for a circuit wired with AWG 14 conductors.
Where should the station’s lightning protection ground system be located?
AnswerOutside the building
Lightning protection is intended to keep lightning current outside the building rather than routing that high-energy current through the operating room.
Which of the following conditions will cause a ground fault circuit interrupter (GFCI) to disconnect AC power?
AnswerCurrent flowing from one or more of the hot wires directly to ground
A GFCI detects an imbalance caused when current leaves the intended hot-to-neutral path and flows to ground. It disconnects power when that ground-fault current is detected.
Which of the following is covered by the National Electrical Code?
AnswerElectrical safety of the station
The National Electrical Code addresses safe electrical installation and wiring practices. It does not set amateur modulation, bandwidth, or RF-exposure limits.
Which of these choices should be observed when climbing a tower using a safety harness?
AnswerConfirm that the harness is rated for the weight of the climber and that it is within its allowable service life
A tower-climbing harness is life-safety equipment. It must be rated for the climber's weight and still be within its approved service life.
What should be done before climbing a tower that supports electrically powered devices?
AnswerMake sure all circuits that supply power to the tower are locked out and tagged
Electrically powered equipment on a tower can expose a climber to dangerous voltage or unexpected movement. Lockout/tagout keeps those circuits from being energized while work is underway.
Which of the following is true of an emergency generator installation?
AnswerThe generator should be operated in a well-ventilated area
Engine-driven generators produce exhaust gases while operating. Running the generator in a well-ventilated area prevents dangerous exhaust accumulation.
Which of the following is a danger from lead-tin solder?
AnswerLead can contaminate food if hands are not washed carefully after handling the solder
Lead from lead-tin solder can be transferred from the hands to food or the mouth. Careful hand washing after handling the solder reduces that contamination risk.
Which of the following is required for lightning protection ground rods?
AnswerThey must be bonded together with all other grounds
Separate grounding systems can rise to different voltages during a lightning event. Bonding the lightning ground rods together with the station's other grounds keeps the grounding system at a common potential as much as practical.
What is the purpose of a power supply interlock?
AnswerTo ensure that dangerous voltages are removed if the cabinet is opened
A power-supply interlock is a safety mechanism that removes dangerous internal voltages when access to the cabinet is opened.
Where should lightning arrestors be located?
AnswerWhere the feed lines enter the building
A lightning arrestor is most effective at the point where the feed line enters the building, before surge energy is carried farther inside.