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There are several hazards related to Amateur Radio, which appropriate practices mitigate.
Thunder, and lightning: The latter is dangerous to station equipment, and potentially the operator. Effective grounding is provided by using ground-rods, and bonding to other grounds, such as metallic water pipes, and the electrical ground of your property. Further measures, such as PolyPhasor or other lighting arresters, are important.
Generally you should avoid operating during a lightning storm, unless using an HT with its own antenna, and no power connection, ideally sitting on a non-conductive chair, inside a house, etc. In any case, lightning crashes make using HF difficult, even if the storm(s) are hundreds of kilometres away.
Exposure at levels significantly above the limits causes heating of body tissue, just as it does to food in a microwave oven.
At microwave frequencies, dishes have high gain, which can concentrate low power levels to dangerous levels. When calculating the level, remember that there is a lack of efficiency in any dish based system: The feed to the dish will either concentrate energy too tightly, making the dish effectively smaller than it is; or it will allow (low intensity) RF to spill outside the dish's area, and thus the power concentrated towards the distant station will be only a portion of the power at the feed-point. 60% efficiency may be typical.
In evaluating exposure, there are two kinds of area, controlled areas, such as work areas on transmitter sites, and your own property as a Ham; and uncontrolled areas, which include your neighbour's house, and public areas. The permissible level in uncontrolled areas is lower than in controlled areas, as there are often time limits on exposure in controlled areas. That your own property is "controlled" means you can make sure your kids don't play in an area where there is a high signal level while you are directing a signal at the rising or setting moon.
The FCC is most strict on levels in the VHF bands, 30 to 300 MHz.
SAR (Specific Absorption Rate) determines how much RF energy is absorbed by the body.
You can read an ARRL article on FCC RF exposure regulation evaluations, and use their RF exposure calculator.
One exemption are hand-held radios sold before May 3, 2021.
The examiner has removed all questions on these, without removing "hazardous materials" from the section title. Maybe the steel of a tower which allows you to reach an elevation from which you will splatter if your fall is hazardous, as they have not added working at heights to the title.
For UHF and microwave electronics, Beryllium Oxide (BeO) is used as a thermal transfer compound within RF transistors, and on older heatsink heat transfer compound. It is a very good electrical insulator, is RF transparent, and is highly thermally conductive (better than many metals). This white substance is toxic, especially if powder is inhaled, and is an irritant to skin and eyes.
The ceramic on magnetrons in military equipment (radars, etc) and in industrial ovens may include it, in white, or tinted pink or salmon / peach. Apparently modern domestic microwave oven magnetrons just use a lower cost ceramic of another kind, often tinted pink (BeO is apparently expensive). More info at: American Beryllia and Wikipedia: Beryllium oxide. Remember that magnetrons use dangerous voltages with a supply capable of supplying lethal current.
Dust from beryllium-copper alloys is also a problem. These are used as they are more springy than straight copper. Mechanical variable frequency HF antennas use this strips of this material internally.
Modern heatsink grease does not contain this. However, if in doubt about the safe use of any substance, download the MSDS - Material Safety Data Sheet.
Polychlorinated Biphenyls (PCBs) are found in older large transformers and capacitors, such as power factor correction capacitors. The latter includes those in fluorescent lamp fittings in commercial premises.
Carbon Monoxide, CO is a colourless, odourless gas which interferes with the blood's ability to deliver oxygen to your organs, including brain. It is generated by internal combustion engines, especially small ones such as used in generators; as well as faulty heaters and water heaters which burn some form of fuel, gas, wood, etc. It can only be detected by a dedicated CO detectors, not by a smoke detector. The symptoms of CO poisoning are the same as influenza, except the sore throat. Children and (other) small mammals are likely to overcome before human adults.
And buying firewood must be more expensive than using electrical heating, and electricity doesn't stink-up your neighbourhood.
Given petrol / gasoline or spark ignition gaseous fuel generators generate few course particulates which will trigger a smoke detector, the device required to detect CO entering a tent or van is the aptly named carbon monoxide detector. These are relatively inexpensive, so worth adding to a communications van, and buying one for home, even where they are not legislated. For Australians Aldi gets them in periodically, or you can ask your local independent or franchise hardware store to order one in from their smoke detector supplier.
BYD, MG, and various other Chinese electric vehicles can supply large amounts of electricity from their traction battery, so can be a great alternative to generators and flame based cooking and heating. These batteries-on-wheels can be periodically driven to a location with a medium to fast charger to recharge.
Two solvents, n-hexane and benzene are for things like cleaning iPhone screens during manufacture, and are carcinogenic, as well as damaging to the central nervous system.
Fumes from solder flux should also be avoided, and if you do a lot of soldering, extractors which suck the fumes and vapours through a carbon filter are available. You no-doubt know that lead (Pb) in solder is also harmful. I've had no difficulties using lead-free solder in hobby PCBs (that is printed circuit boards).
Ethanol (C2H5OH) (the primary constituent in methylated spirits (metho) or denatured alcohol, along with the very toxic methanol) used for cleaning and as a solvent for things like French polishing timber is flammable, with a flame which can be difficult to see. Consumption of this compound in beverages can cause accidents if done before working on equipment with hazardous voltages, etc; and it makes you look old before your time! Methanol (CH3OH) poisoning is surprisingly common in the US, and occurs elsewhere via local unlicensed spirit production. It is literally a case of "Stop it, or you'll go blind". Or require expensive body repatriation. Both are eye irritants if splashed.
Metho or other alcohol can apparently cause explosions if used in some oil or keroscene lamps.
While ethanol may be used in windscreen washer additive with anti-freeze properties in Europe and Australia, in the US and Canada they use methanol, hence the high poisoning rate in the US (yes, idiots drink it). Even in warmer areas the ethanol ones are worth using, as they are very effective at removing gunk. VW, Cupra / Seat, Audi, and Škoda dealers should either stock it, or be able to get it in. Würth "Windscreen cleaner Screenwash Plus" is available with article number: 0892332840. Follow the instructions, but in all of Australia the minimum quantity should be adequate. Note that this in *NOT* antifreeze engine coolant.
Climbing towers involves the risk of a fall. Thus you should wear a full harness with over-shoulder straps, not just an old fashioned belt. This should include two lanyards which have large sprung hooks which can attach to tower legs. This allows one or other to be clipped to the tower at any one time, termed "10% tie-off". These should include some form of fall arrest system which prevents a sudden stop if falling. This may be something like webbing folded back on itself at several points, and sewn, such that a shock load causes the stitching to fail progressively; or an aluminium plate in a squiggled form which straightens somewhat when overloaded. These should be attached above head height, presumably to reduce the distance of any fall.
When properly worn and attached it is possible to lean back onto the harness to allow both hands to be used.
Tower Safety, and Working at Height courses also available.
You should read something more comprehensive on tower climbing before you do so, including all manuals provided with the harnesses and lanyards.
With any energy storage system, one factor determining the danger it poses is how rapidly the energy can be released when something goes wrong. Does a seized bearing or failed shaft cause a vehicle with energy stored in a very large flywheel to rip itself apart instantly, while a bus burning due to a fuel or very rare battery fire provides time to exit? Lithium batteries without effective management systems (BMS) can also pose a risk.
These are the actual questions from the Extra licence exam pool, as published by the NCVEC.
E0A01
What is the primary function of an external earth connection or ground rod?
A. Prevent static build up on power lines
B. Lightning charge dissipation
C. Reduce RF current flow between pieces of equipment
D. Protect breaker panel from power surges
Earthing is primarily a protection against lighting, answer B.
As well as taking energy from the strike, or a nearby strike to ground, the earth system can dissipate the large static charge which could otherwise accumulate on an ungrounded antenna. There possible antennas should be grounded when not in use. Wind and rain or snow can also cause a charge to build up on antennas and guy wires. It can even cause audible pops due to discharge across insulators on guy wires of large masts.
E0A02
When evaluating RF exposure levels from your station at a neighbor's home, what must you do?
A. Ensure signals from your station are less than the controlled maximum permissible exposure (MPE) limits
B. Ensure signals from your station are less than the uncontrolled maximum permissible exposure (MPE) limits
C. Ensure signals from your station are less than the controlled maximum permissible emission (MPE) limits
D. Ensure signals from your station are less than the uncontrolled maximum permissible emission (MPE) limits
It must be below the uncontrolled area EXPOSURE limits, answer B.
The emission level does not matter, it is the exposure. If you lived in a rural estate or farm you could emit a high power signal into a gain antenna and not exceed the exposure limit a a house a hundred or more metres away. It is "uncontrolled" because it is not a workplace. Joking comment: If they WFH does that mean you could apply the "controlled" level in their work hours? No, because it is not somewhere you control. That said apparently you can exceed the safe level if you know the property is unoccupied.
E0A03
Over what range of frequencies are the FCC human body RF exposure limits most restrictive?
A. 300 kHz to 3 MHz
B. 3 to 30 MHz
C. 30 to 300 MHz
D. 300 to 3000 MHz
This is the VHF range, 30 to 300 MHz, answer C.
E0A04
When evaluating a site with multiple transmitters operating at the same time, the operators and licensees of which transmitters are responsible for mitigating over-exposure situations?
A. Each transmitter that produces 20 percent or more of its MPE limit in areas where the total MPE limit is exceeded
B. Each transmitter operating with a duty cycle greater than 25 percent
C. Each transmitter that produces 5 percent or more of its MPE limit in areas where the total MPE limit is exceeded
D. Each transmitter operating with a duty-cycle greater than 50 percent
You club may either pay for, or be granted access to a radio communication site with government and/or volunteer service and/or commercial users. If there is a problem with exposure in public areas around the site, and your club owns a transmitter with produces 5% of the MPE limit, you must take part in mitigation measures, answer C.
E0A05
What hazard is created by operating at microwave frequencies?
A. Microwaves are ionizing radiation
B. The high gain antennas commonly used can result in high exposure levels
C. Microwaves are in the frequency range where wave velocity is higher
D. The extremely high frequency energy can damage the joints of antenna structures
A dish can easily provide 30 dB of gain, converting a 1 watt input into a kilowatt in the direction it is pointing, but instead of a poor dead chook in the microwave, it could be your body parts being cooked! Answer B.
This question has been modified to incorrectly imply that all microwave systems generate supposedly dangerous levels. A HT on 1.290 GHz (23 cm) isn't going generate high levels, even if the wavelength is short enough that a rubber-ducky antenna is not horribly inefficient. The same applies with a low power video sender on 5.6 GHz into a pay-TV dish. However, if you are using a IC-905 into a dish at home, the RF should be well above head height. If operating with a antenna on a speaker stand, tripod or similar, try to set it up so people can't get in front of it.
E0A06
Why are there separate electric (E) and magnetic (H) MPE limits at frequencies below 300 MHz?
A. The body reacts to electromagnetic radiation from both the E and H fields
B. Ground reflections and scattering cause the field strength to vary with location
C. E field and H field radiation intensity peaks can occur at different locations
D. All these choices are correct
All of the above, answer D.
E0A07
What is meant by "100% tie-off" regarding tower safety?
A. All loose ropes and guys secured to a fixed structure
B. At least one lanyard attached to the tower at all times
C. All tools secured to the climber's harness
D. All circuit breakers feeding power to the tower must be tied closed with tape, cable, or ties
This means as you climb a tower, or reposition yourself on it, or are working on an antenna, etc, you always have at least one lanyard attached, answer B.
E0A08
What does SAR measure?
A. Signal attenuation ratio
B. Signal amplification rating
C. The rate at which RF energy is absorbed by the body
D. The rate of RF energy reflected from stationary terrain
SAR is the rate at which energy is absorbed by the body, answer C.
E0A09
Which of the following types of equipment are exempt from RF exposure evaluations?
A. Transceivers with less than 7 watts of RF output
B. Antennas that radiate only in the near field
C. Hand-held transceivers sold before May 3, 2021
D. Dish antennas less than one meter in diameter
These are hand-held transceivers sold before May 3, 2021, answer C.
E0A10
When must an RF exposure evaluation be performed on an amateur station operating on 80 meters?
A. An evaluation must always be performed
B. When the ERP of the station is less than 10 watts
C. When the station's operating mode is CW
D. When the output power from the transmitter is less than 100 watts
These must always be performed, answer A.
Thankfully, at this frequency if the antenna is over 1.5 metres from a fence it easily complies at many hundred watts. At 100 watts it is 20 cm or less in most cases, so using a wire on the top rail of a timber fence in an HOA is safe within a hand-span of the fence.
E0A11
To what should lanyards be attached while climbing?
A. Antenna mast
B. Guy brackets
C. Tower rungs
D. Tower legs
This is the tower legs, answer D.
I suppose that the logic here is that if the tower is standing the legs must be in reasonable condition, while cross-bars or rungs may not be.
E0A12
Where should a shock-absorbing lanyard be attached to a tower when working above ground?
A. Above the climber's head level
B. To the belt of the fall-arrest harness
C. Even with the climber's waist
D. To the next lowest set of guys
At the tower end, the lanyard should be attached above the climber's head, answer A.
Harnesses should have over-shoulder straps, and the lanyard should be attached above belt level.
CONGRATULATIONS! You have now reviewed all questions.
I would suggest doing some drills on hamtestonline.com, which are available without charge. Registering, also free, allows you to track your results.
It is also time to look at Exams.
You can find links to lots more on the Learning Material page.
This has taken a fair bit of work to write, so if you have found this useful, there is a "tip jar" and a Ko-Fi link below.
You may also want to get a Ham related shirt designed by your author: VK-73
Another path of study is become a Volunteer Examiner with one of the various VECs. The ARRL-VEC has a comprehensive manual, which includes an open-book review as part of the application. See: Becoming a VE. GLAARG are also worth talking too, or one of the other local VECs.
Written by Julian Sortland, VK2YJS & AG6LE, March 2025.
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