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G0B

ELECTRICAL AND RF SAFETY

- Station safety: electrical shock, grounding, fusing, interlocks, and wiring; antenna and tower safety

G0B011 of 13

Which wire or wires in a four-conductor 240 VAC circuit should be attached to fuses or circuit breakers?

Why A four-conductor 240 VAC feed has two ungrounded "hot" conductors plus a neutral and a safety ground. Overcurrent protection goes only in the ungrounded conductors, because those are the ones that can deliver fault current from the source. The National Electrical Code prohibits putting a fuse or breaker in a grounded (neutral) or grounding conductor, since opening one would leave the equipment chassis or circuit energized with no return or no safety path.

Watch out The choice that fuses all wires sounds safer but is actually dangerous: if the neutral fuse blows first, the load stays connected to a hot line at full potential, and a broken ground connection removes the very protection that trips the breaker during a fault.

Fuse the hots, never the neutral or the green wire. Protection interrupts the source, not the return or safety path.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B022 of 13

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?

Why The National Electrical Code matches conductor size to breaker rating so the wire can carry the fault current without overheating before the breaker trips. For common copper branch circuits the pattern is AWG 14 for 15 amps, AWG 12 for 20 amps, and AWG 10 for 30 amps. So a 20-amp breaker requires at least AWG number 12 copper wire.

Watch out AWG 16 and AWG 20 are thinner wire (larger AWG number means smaller conductor) and would overheat well before a 20-amp breaker opened; AWG 8 is heavy enough but far larger than the minimum the question asks for.

14-15, 12-20, 10-30: wire gauge counts down as amps count up.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B033 of 13

Which size of fuse or circuit breaker would be appropriate to use with a circuit that uses AWG number 14 wiring?

Why A fuse or breaker protects the wire, not the equipment, so it must open before the conductor can overheat. Under the National Electrical Code, AWG 14 copper branch-circuit wire is limited to 15 amperes, so a 15 A breaker or fuse is the largest allowed. Using anything bigger lets the wire carry more current than its insulation and ampacity rating allow, creating a fire hazard.

Watch out The 20 ampere choice is the correct rating for the next larger wire, AWG 12, not for AWG 14; oversizing the breaker means the wire fails before the protection trips.

14-15, 12-20, 10-30: smaller gauge number, bigger wire, bigger breaker.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B044 of 13

Where should the station's lightning protection ground system be located?

Why Lightning protection works by giving surge current a short, direct path to earth before it can enter the building. Coax shields, rotator and control lines should pass through surge arrestors mounted on a ground panel or entry plate outside the structure, bonded to ground rods driven into the earth there. That ground system must also be bonded back to the AC service entrance ground so everything rises and falls in potential together, which is what prevents damaging differences between grounds.

Watch out Putting the lightning ground right at the operating position sounds convenient but it drags the surge current through the building and through your equipment on its way to earth, which is exactly what you are trying to avoid.

Stop the strike at the door: arrestors and ground rods go outside, bonded to the service ground.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B055 of 13

Which of the following conditions will cause a ground fault circuit interrupter (GFCI) to disconnect AC power?

Why A GFCI continuously compares the current leaving on the hot conductor with the current returning on the neutral. Those should be equal; if they differ by roughly 5 milliamps, some current is escaping to ground, possibly through a person, and the device trips in a fraction of a second. So it is current leaking from hot directly to ground that causes the disconnect, not the size of the load current.

Watch out Current from hot to neutral is simply normal load current, which a GFCI ignores no matter how large; overcurrent is the job of the fuse or breaker, and overvoltage is handled by surge protection, not a GFCI.

GFCI = balance check. Hot out must equal neutral back; about 5 mA going missing to ground trips it.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B066 of 13

Which of the following is covered by the National Electrical Code?

Why The National Electrical Code (NFPA 70) is a building/wiring safety standard, not an FCC rule. It specifies things like conductor sizes, overcurrent protection, grounding and bonding, and safe installation practices, so for a ham station it governs the AC wiring, service entrance, station ground and lightning protection. Bandwidth, modulation and RF exposure limits come from FCC Part 97, not the NEC.

Watch out RF exposure is the tempting pick because it sounds like a safety topic, but human RF exposure limits come from the FCC (Part 97 and the OET Bulletin 65 guidance derived from IEEE/NCRP), not the electrical code.

NEC = wires and grounds (AC safety); FCC Part 97 = signals and RF exposure.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B077 of 13

Which of these choices should be observed when climbing a tower using a safety harness?

Why A climbing safety harness is life-support equipment, so before you leave the ground you verify it is rated for your weight (including tools and gear) and that it has not passed the manufacturer's stated service life. Webbing and stitching degrade from UV exposure, moisture, and abrasion, so an old or damaged harness can fail at exactly the moment it is needed. Any harness that has taken a fall or shows cuts, fraying, or corroded hardware should be retired.

Watch out Holding the tower with one hand is good climbing practice but it is not what makes a harness safe, and hanging heavy tools on the harness is actually discouraged since tools should be hauled up separately on a rope, so the choice saying all are correct fails too.

The harness question is about the harness: right weight rating, not past its expiration date.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B088 of 13

What should be done before climbing a tower that supports electrically powered devices?

Why Rotators, antenna relays, tower lighting and amplifier feed lines on a tower can carry hazardous voltage, so the standard industrial practice of lockout/tagout applies: open the breakers or disconnects feeding those circuits, lock them in the off position, and tag them so no one can restore power while you are aloft. This guarantees the circuits stay dead even if someone else walks by the panel and flips a switch. Verifying the power is off at the tower before you start climbing is part of the same routine.

Watch out Ungrounding the tower base is exactly backward, since the ground connection protects against lightning and fault currents and should never be removed; the electric company has no involvement in your own station wiring.

Lock it out and tag it out before you go up. Never disconnect the ground.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B099 of 13

Which of the following is true of an emergency generator installation?

Why Engine driven generators produce carbon monoxide, an odorless, colorless gas that can be lethal indoors or in a partially enclosed space, so the unit must run outdoors or in a space with good airflow and exhaust directed away from occupied areas. Proper ventilation also carries away engine heat. Safe generator practice is ventilation, correct grounding/bonding, and keeping fuel stored well away from the hot running engine.

Watch out Insulating the generator from ground is backwards: the frame and neutral bonding must follow electrical code so fault current has a safe path. Storing fuel next to the generator puts gasoline vapors beside a hot exhaust and ignition sources, a fire risk, so 'all these choices' cannot be right.

Generators: fresh air yes, fuel nearby no, floating ground no. CO kills quietly.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B1010 of 13

Which of the following is a danger from lead-tin solder?

Why Traditional electronics solder is roughly 60% tin and 40% lead, and lead is a cumulative toxin. Handling the solder or the residue leaves traces on your hands, and those traces can transfer to food, drinks, or your mouth if you do not wash up afterward. The hazard is ingestion of lead residue, not the fumes from soldering (which are mostly flux smoke), so wash your hands after any soldering session.

Watch out The claims about solder disintegrating under high voltage, tin cold-flowing into shorts, or RF turning lead into poison gas are not real phenomena; they sound technical but describe nothing that actually happens in a station.

Lead solder: wash your hands before you eat. The only realistic answer is the mundane hygiene one.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B1111 of 13

Which of the following is required for lightning protection ground rods?

Why Lightning protection works by keeping everything in the station at the same potential during a strike, so every ground rod, the electrical service ground, and the tower and entry-panel grounds must be bonded together into one single-point ground system. If two ground systems are separate, a surge can raise one thousands of volts above the other and the difference flashes through your equipment. The National Electrical Code (Article 250) requires this bonding of all grounding electrodes at a structure.

Watch out The choice about right-angle bends states the opposite of good practice: sharp bends add inductance and let the surge jump off the conductor, so ground wires should use gentle, sweeping bends.

One station, one ground: bond every rod and ground together, and keep ground wire bends gentle, never sharp.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B1212 of 13

What is the purpose of a power supply interlock?

Why An interlock is a safety switch wired into the cabinet or enclosure so that opening the case breaks the primary power circuit. Power supplies and amplifiers can hold hundreds or thousands of volts on filter capacitors and plate circuits, so the interlock removes the source of that voltage the moment the cover comes off. It protects the operator from contacting lethal potentials during service. Note that large filter capacitors can still hold a charge after power is removed, so bleeder resistors and a shorting stick are still good practice.

Watch out Shutting down on overheating describes a thermal cutout or thermostat, and shutting down on excess voltage describes an overvoltage crowbar circuit. Neither responds to the cabinet being opened.

Interlock = "open the lid, kill the volts." It senses the cabinet, not heat or voltage.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

G0B1313 of 13

Where should lightning arrestors be located?

Why Lightning protection works by giving surge energy a short, low-impedance path to earth before it can get inside. So coax and other feed lines should pass through arrestors mounted on a bonded entrance panel right where they enter the building, with that panel tied to the station ground and to the building's electrical grounding electrode system. Anything that gets past that point is already in your shack.

Watch out Putting the arrestor out at the antenna or at a distant power pole ground leaves a long run of feed line inside or near the structure still able to carry the surge, and an arrestor in series with a ground lead would defeat the low-impedance bond the ground lead is supposed to provide.

Stop the surge at the door: arrestors go at the entrance panel, bonded to the station ground.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

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