T0 — Safety

3 exam questions · 3 groups · 36 questions in pool

The part that keeps you alive: electrical and battery hazards and proper grounding/fusing; tower and antenna safety; and RF exposure. There are no calculations to fear here — almost every answer follows from common sense plus a few specific numbers and the idea that you, the licensee, are responsible for safety.

T0A — Power Circuits, Hazards, Fuses, Grounding, Lightning, Batteries

12 questions

What this group tests: household AC wiring conventions, fuses, grounding/bonding, lightning protection, and battery hazards.

Foundational concepts

Fuses exist to remove power during an overload; they protect the wiring from overheating. So a fuse must be installed in series with the hot conductor, and you must never replace a 5 A fuse with a 20 A one — the oversized fuse lets excessive current flow and start a fire. In U.S. 120 V wiring, black insulation = the hot conductor.

Electric shock through the body can cause many injuries — “all of these” — so guarding against shock uses several measures (“all of these”). Two non-obvious electrical hazards: a power supply can still bite you right after you switch it off, because filter capacitors hold a charge; and when measuring high voltage, your voltmeter and leads must be rated for it.

Grounding/lightning: a lightning arrester goes on a grounded panel where the feed lines enter the building, and all external ground rods must be bonded together with heavy wire or strap (a single common ground prevents dangerous voltage differences).

Batteries: shorting a 12 V storage battery’s terminals can cause burns, fire, or explosion; charging or discharging too quickly causes overheating or out-gassing (venting explosive hydrogen).

Key facts to retain

External reference anchors

Per-question map

Q Asks for Resolved by
T0A01 12 V battery hazard Shorting → burns/fire/explosion
T0A02 Current through the body All these choices
T0A03 Black wire = which conductor Hot
T0A04 Purpose of a fuse Remove power on overload
T0A05 Why not 5 A → 20 A fuse Excess current could cause fire
T0A06 Guarding against shock All these choices
T0A07 Where lightning arrester goes Grounded panel at building entry
T0A08 Where fuse/breaker goes In series with hot only
T0A09 All external ground rods Bond together with heavy wire/strap
T0A10 Too-fast battery charge/discharge Overheating or out-gassing
T0A11 Hazard right after power-off Charge in filter capacitors
T0A12 High-voltage measurement precaution Use rated meter and leads

T0B — Antenna and Tower Safety

11 questions

What this group tests: the physical safety of erecting and climbing towers and antennas, and tower grounding.

Foundational concepts

The dominant hazard around antenna work is power lines. When installing an antenna, keep enough distance that if it falls, no part can come within 10 feet of the power wires; look for and stay clear of overhead wires; and never attach an antenna to a utility pole (it could contact high-voltage lines).

Climbing rules are strict: never climb a tower without a helper/observer, and always use proper equipment (“all of these” required). A crank-up tower must not be climbed unless fully retracted or with mechanical safety locks in place. A safety wire through a turnbuckle keeps guy-line tension from vibrating loose.

Tower grounding for lightning wants the fastest possible path to earth: connections short and direct, sharp bends avoided (lightning won’t make a tight turn), separate 8-foot ground rods for each tower leg, all bonded together and to the tower. The authority that sets these grounding requirements is your local electrical code.

Key facts to retain

External reference anchors

Per-question map

Q Asks for Resolved by
T0B01 Good tower ground wire practice Short and direct connections
T0B02 Required when climbing All these choices
T0B03 Climb without observer? Never
T0B04 Important install precaution Stay clear of overhead wires
T0B05 Turnbuckle safety wire purpose Prevent vibration loosening
T0B06 Min distance from power line 10 ft clearance if it falls
T0B07 Crank-up tower rule Climb only retracted/locked
T0B08 Proper tower grounding A bonded 8-ft rod per leg
T0B09 Avoid utility poles because Could contact high-voltage lines
T0B10 Lightning conductor install Avoid sharp bends
T0B11 Who sets grounding requirements Local electrical codes

T0C — RF Exposure

13 questions

What this group tests: the nature of RF radiation, the FCC exposure limits and what affects them, and how to stay compliant.

Foundational concepts

RF is non-ionizing radiation — unlike X-rays or radioactivity, it lacks the energy to cause chemical changes or damage DNA. Its hazard is heating: touching a transmitting antenna causes an RF burn to the skin.

Several factors set the maximum permissible exposure (MPE), and they all interact — “all of these” affect exposure near an antenna. Frequency matters because the body absorbs RF more efficiently at some frequencies than others; the limit is most restrictive (lowest) around 50 MHz, near where the body resonates. Duty cycle — the percentage of time the transmitter is actually transmitting — matters because it sets the average exposure: cutting duty cycle from 100% to 50% doubles the allowable power density (you may run twice the power for half the airtime).

Staying compliant is the licensee’s responsibility. You may evaluate your station by any acceptable method (“all of these”), you must re-evaluate whenever you change the transmitter or antenna system, and the simplest fix to reduce exposure is to relocate antennas farther from people.

Key facts to retain

External reference anchors

Per-question map

Q Asks for Resolved by
T0C01 Type of radiation radio is Non-ionizing
T0C02 Lowest MPE frequency 50 MHz
T0C03 Duty cycle 100%→50% Allowed density ×2
T0C04 Factors affecting RF exposure All these choices
T0C05 Why limits vary with frequency Body absorbs more at some frequencies
T0C06 Acceptable compliance methods All these choices
T0C07 Touching antenna during TX RF burn to skin
T0C08 Reduce RF exposure Relocate antennas
T0C09 Staying compliant Re-evaluate after system changes
T0C10 Why duty cycle matters Affects average exposure
T0C11 Definition of duty cycle % of time transmitting
T0C12 RF vs ionizing radiation RF can’t damage DNA
T0C13 Who’s responsible for exposure The station licensee