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Amateur Radio Info & Exams - Safety - Earthing, RF hazards & Hazardous materials

There are several hazards related to Amateur Radio, which appropriate practices mitigate.

Donner unt Blitzen!

Thunder, and lightning, at least the latter is dangerous to station equipment, and potentially the operator. Effective grounding, through ground-rods, and bonding to other grounds. Measures, such as PolyPhasor lighting arrestors, are important.

RF Exposure

Exposure at levels significantly above the limits causes heating of body tissue, just as it does to food in a microwave oven. And at microwave frequencies, dishes have high gain, which can concentrate low power levels to dangerous levels.

In evaluating exposure, there are two kinds of area, controlled areas, such as work areas on transmitter sites; 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.

Toxic materials

For UHF and microwave electronics, Beryllium Oxide is or was used as a thermal transfer compound in transistors. This white substance is toxic, especially if powder is inhaled. Modern heatsink grease does not contain this.

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 small mammals are likely to overcome before adults.

Off the exam, n-hexane and benzene are solvents used in 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.

Relevant Questions

These are the actual questions from the Extra licence exam pool, as published by the NCVEC.

What is the primary function of an external earth connection or ground rod?
A. Reduce received noise
B. Lightning protection
C. Reduce RF current flow between pieces of equipment
D. Reduce RFI to telephones and home entertainment systems

Earthing is primarily a protection against lighting, answer B.

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 Permitted Exposure (MPE) limits
B. Ensure signals from your station are less than the uncontrolled Maximum Permitted Exposure (MPE) limits
C. Ensure signals from your station are less than the controlled Maximum Permitted Emission (MPE) limits
D. Ensure signals from your station are less than the uncontrolled Maximum Permitted Emission (MPE) limits

It must be below the uncontrolled area limits, answer B.

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.

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. Only the most powerful transmitter
B. Only commercial transmitters
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.

What is one of the potential hazards of operating in the amateur radio microwave bands?
A. Microwaves are ionizing radiation
B. The high gain antennas commonly used can result in high exposure levels
C. Microwaves often travel long distances by ionospheric reflection
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 is your body parts getting cooked! Answer B.

Why are there separate electric (E) and magnetic (H) field MPE limits?
A. The body reacts to electromagnetic radiation from both the E and H fields
B. Ground reflections and scattering make the field impedance vary with location
C. E field and H field radiation intensity peaks can occur at different locations
D. All of these choices are correct

All of the above, answer D.

How may dangerous levels of carbon monoxide from an emergency generator be detected?
A. By the odor
B. Only with a carbon monoxide detector
C. Any ordinary smoke detector can be used
D. By the yellowish appearance of the gas

Odourless, colourless GAS, so no smell, no yellow, and no particles which will trigger a smoke detector, so the required device must be the aptly named carbon monoxide detector! Answer B.

What does SAR measure?
A. Synthetic Aperture Ratio of the human body
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.

Which insulating material commonly used as a thermal conductor for some types of electronic devices is extremely toxic if broken or crushed and the particles are accidentally inhaled?
A. Mica
B. Zinc oxide
C. Beryllium Oxide
D. Uranium Hexafluoride

It is Beryllium Oxide, a white material, answer C.

Dust from beryllium-copper alloys is also a problem. These are used as they are more springy than straight copper.

What toxic material may be present in some electronic components such as high voltage capacitors and transformers?
A. Polychlorinated Biphenyls
B. Polyethylene
C. Polytetrafluroethylene
D. Polymorphic silicon

Polychlorinated Biphenyls (PCB) is an often clear oily liquid which is toxic, answer A.

PE is a common plastic, and PTFE is trademarked as Teflon.

Which of the following injuries can result from using high-power UHF or microwave transmitters?
A. Hearing loss caused by high voltage corona discharge
B. Blood clotting from the intense magnetic field
C. Localized heating of the body from RF exposure in excess of the MPE limits
D. Ingestion of ozone gas from the cooling system

It is heating of body parts, answer C.

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 yoru 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" below.

You may also want to get a Ham related shirt designed by your author: VK-73

The other path of study is become a Volunteer Examineer with one of the various VECs. The ARRL-VEC has a comprehensive manual, which includes an open-book review as part of the application: Becoming a VE.

Written by Julian Sortland, VK2YJS & AG6LE, July 2022.

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