A.R.E.S. Antenna and RF Safety By: Jeffrey Lamb Firefighter/EMT Sacramento County A.R.E.S. AEC We are amateur radio operators. We have a awesome hobby. We are A.R.E.S and we use our radio equipment to help in times of emergency and disaster. The radio equipment we use does present significant dangers to us and to others. We need to be highly aware of these dangers. We need to act responsibly and operate our radios responsibly so that we and the community are safe around antennas and RF energy. Let's look at antenna and RF safety.
Antennas!!! Some have said the antenna is the most important part of amateur radio. Well, if this is true, try holding an antenna in your hand with nothing attached to it and see how far and how well you can communicate with it. Having said this, antennas are critical to amateur radio. A better antenna is always preferable to more power. The better the antenna, the better your signal gets out. What good is your radio if there is not an antenna hooked up to it? So... what do we need to consider in antenna safety? We need to keep ourselves, others, and the antenna itself safe. Antennas can be a base antenna (typically fixed/non portable) or mobile/portable. Base antennas need to be installed correctly. When installing a base antenna, one must ALWAYS be INTENSLY AWARE of nearby power lines and keep well clear of them. Antenna tower collapsed into high power wires.
Base antennas need to be installed in a location where people and animals will not run into the antenna and injure themselves or damage the antenna. Base antennas may have elements/parts that stick out and could cause a penetrating injury to people and animals. Try to install the antenna high enough that people and animals can easily pass under the antenna if necessary without being injured or damaging the antenna. Be careful to make the antenna support as visible as possible to avoid people and animals running into the antenna support also. When installing a base antenna, carefully consider the winds it may be exposed to. Is your base antenna installation strong enough to survive the winds your location may be exposed to? If the wind blows over your antenna, what people, animals, or property will it damage when it crashes down?
When installing a base antenna system, be careful to consider proper proper electrical and RF grounding. An antenna may need to be properly grounded so that it radiates the RF energy efficiently. It is also CRITICAL that it is properly grounded against lightning strikes. RF grounding. Different than grounding for lightning protection. In the USA around a 100 residents are killed by lightning every year. The initial lightning strike can also be followed by secondary strokes utilising the same ionised air channel. Up to 4 secondary strokes can be expected, though much higher counts have been recorded. Each lightning stroke typically lasts only last 10 to 50 microseconds (0.000050 sec) and carries hundreds to thousands of amps. The air around a lightning strike is typically superheated to about 20,000 degrees Celsius or over 3 times hotter than the surface of the sun (estimated at 5,500 C). The air temperature can range from 8,000 to 30,000 degrees Celsius. The estimated peak power per lightning stroke is 10^12 watts (1,000,000,000,000 watts or 1,000 Giga Watts). The total energy in a large thunderstorm is thought to be enough to power the whole of the USA for 20 minutes. An average lightning strike discharges about 30,000 amperes (20,000 amperes in the UK). The current in a lightning strike typically ranges from 5,000 to 50,000 amperes depending on the strength of storm. NASA has recorded strikes of 100,000 amperes and there are other reports of strikes over 200,000 amperes. Lightning can and does strike the same place twice. On average lightning strikes the Empire State Building in New York City about 100 times every year. 49 strikes have been recorded in a single day.
Lightning strikes to base antenna systems must be taken extremely seriously. An in line coax lightning protector. Other brands and models available Whatever your base antenna system is, make sure it is well protected against lightning. Base antennas have a signal fed to them. This may be through coax antenna cable or other feed lines. Be aware that these feed lines can be a tripping hazard. When installing antenna feed lines, be aware of tripping hazards and other hazards which would damage the feed line or cause secondary damage to the antenna or radio/amplifier. If coax antenna cable or other feed line is being run overhead, make sure that it is high enough that people and animals can pass under it without being injured.
Other hazards may be present. Antennas on vehicles We love to take our amateur radio with us. There are some antenna safety precautions and considerations with antennas on vehicles to be aware of.
Make sure that antennas mounted on a vehicle are secure and will not be blown off by winds from the vehicle moving and or windy weather. If you have a problem with an antenna... which one??? Try and keep your ambitions a bit more realistic
Be aware of how high your antenna(s) extend above your vehicle. You may have problems when traveling through tunnels, under overpasses, entering garages, low hanging tree branches, and fast food drive through lanes. Handheld Radio Antennas Handheld radio antennas come in many styles and sizes. Some are very flexible, others are not. Some handheld radio antennas telescope and extend, others do not. Always be aware when others are around you when you are using your handheld radio. Be careful to make sure that your antenna doesn't poke you or anyone else in the eye. Be careful when your radio is not in your hands that the antenna is not damaged. The antenna might easily be bent or broken and might be rendered useless. Always examine the antenna prior to use for damage. Make sure the antenna is properly secured to the radio. An antenna not properly atached to the radio or missing can cause damage to the radio. Make sure that the antenna is correct for the radio you are going to use it on. Using the wrong antenna may cause as much damage as not having an antenna on the radio.
RF Exposure and Safety Amateur Radio is basically a safe activity. In recent years, however, there has been considerable discussion and concern about the possible hazards of electromagnetic radiation, including both RF energy and power-frequency (50-60 Hz) electromagnetic fields. To allay such concerns, the FCC set limits on the amount of RF energy people can be exposed to. All amateur radio operators are responsible to to make sure that they are in compliance with the RF exposure limits set by the FCC, FCC Policy on Human Exposure to Radio frequency Electromagnetic Fields The FCC is required by the National Environmental Policy Act of 1969,among other things, to evaluate the effect of emissions from FCC-regulated transmitters on the quality of the human environment. Several organizations, such as the American National Standards Institute (ANSI), the Institute of Electrical and Electronics Engineers, Inc. (IEEE),and the National Council on Radiation Protection and Measurements (NCRP) have issued recommendations for human exposure to RF electromagnetic fields. On August 1, 1996, the Commission adopted the NCRP's recommended Maximum Permissible Exposure limits for field strength and power density for the transmitters operating at frequencies of 300 khz to 100 GHz. In addition, the Commission adopted the specific absorption rate (SAR) limits for devices operating within close proximity to the body as specified within the ANSI/IEEE C95.1-1992 guidelines. Radio waves and microwaves emitted by transmitting antennas are one form of electromagnetic energy. They are collectively referred to as "radiofrequency" or "RF" energy or radiation. Note that the term radiation does not mean radioactive. Often, the terms "electromagnetic field" or "radiofrequency field" may be used to indicate the presence of electromagnetic or RF energy. The RF waves emanating from an antenna are generated by the movement of electrical charges in the antenna. Electromagnetic waves can be characterized by a wavelength and a frequency. The wavelength is the distance covered by one complete cycle of the electromagnetic wave, while the frequency is the number of electromagnetic waves passing a given point in one second. The frequency of an RF signal is usually expressed in terms of a unit called the "hertz" (abbreviated "Hz"). One Hz equals one cycle per second. One megahertz ("MHz") equals one million cycles per second.
Different forms of electromagnetic energy are categorized by their wavelengths and frequencies. The RF part of the electromagnetic spectrum is generally defined as that part of the spectrum where electromagnetic waves have frequencies in the range of about 3 kilohertz (3 khz) to 300 gigahertz (300 GHz). Microwaves are a specific category of radio waves that can be loosely defined as radiofrequency energy at frequencies ranging from about 1 GHz upward. "Ionization" is a process by which electrons are stripped from atoms and molecules. This process can produce molecular changes that can lead to damage in biological tissue, including effects on DNA, the genetic material of living organisms. X-rays and gamma rays are examples of ionizing radiation. The energy levels associated with RF and microwave radiation, on the other hand, are not great enough to cause the ionization of atoms and molecules, and RF energy is, therefore, is a type of non-ionizing radiation. Other types of non-ionizing radiation include visible and infrared light. Ionizing radiation should not be confused with the lower-energy, non-ionizing radiation with respect to possible biological effects, since the mechanisms of action are quite different. WHAT BIOLOGICAL EFFECTS CAN BE CAUSED BY RF ENERGY? Biological effects can result from exposure to RF energy. Biological effects that result from heating of tissue by RF energy are often referred to as "thermal" effects. It has been known for many years that exposure to very high levels of RF radiation can be harmful due to the ability of RF energy to heat biological tissue rapidly. This is the principle by which microwave ovens cook food. Exposure to very high RF intensities can result in heating of biological tissue and an increase in body temperature. Tissue damage in humans could occur during exposure to high RF levels because of the body's inability to cope with or dissipate the excessive heat that could be generated.
Two areas of the body, the eyes and the testes, are particularly vulnerable to RF heating because of the relative lack of available blood flow to dissipate the excess heat load. At relatively low levels of exposure to RF radiation, i.e., levels lower than those that would produce significant heating; the evidence for production of harmful biological effects is ambiguous and unproven. Such effects, if they exist, have been referred to as "non-thermal" effects. A number of reports have appeared in the scientific literature describing the observation of a range of biological effects resulting from exposure to low-levels of RF energy. However, in most cases, further experimental research has been unable to reproduce these effects. Furthermore, since much of the research is not done on whole bodies (in vivo), there has been no determination that such effects constitute a human health hazard. It is generally agreed that further research is needed to determine the generality of such effects and their possible relevance, if any, to human health. In the meantime, standards-setting organizations and government agencies continue to monitor the latest experimental findings to confirm their validity and determine whether changes in safety limits are needed to protect human health. ARE RF EMISSIONS FROM AMATEUR RADIO STATIONS HARMFUL? There are hundreds of thousands of amateur radio operators ("hams") worldwide. Amateur radio operators in the United States are licensed by the FCC. The Amateur Radio Service provides its members with the opportunity to communicate with persons all over the world and to provide valuable public service functions, such as making communications services available during disasters and emergencies. Like all FCC licensees, amateur radio operators are required to comply with the FCC's guidelines for safe human exposure to RF fields. Under the FCC's rules, amateur operators can transmit with power levels of up to 1500 watts. However, most operators use considerably less power than this maximum. Studies by the FCC and others have shown that most amateur radio transmitters would not normally expose persons to RF levels in excess of safety limits. This is primarily due to the relatively low operating powers used by most amateurs, the intermittent transmission characteristics typically used and the relative inaccessibility of most amateur antennas. As long as appropriate distances are maintained from amateur antennas, exposure of nearby persons should be well below safety limits. To help ensure compliance of amateur radio facilities with RF exposure guidelines, both the FCC and American Radio Relay League (ARRL) have issued publications to assist operators in evaluating compliance for their stations. See Sacramento County A.R.E.S website under training B 040 FCC OET Bulletin 65
WHERE CAN I OBTAIN MORE INFORMATION ON POTENTIAL HEALTH EFFECTS OF RADIOFREQUENCY ENERGY? EPA: The Environmental Protection Agency's Office of Radiation Programs is responsible for monitoring potential health effects due to public exposure to RF fields. Contact: Environmental Protection Agency, Office of Radiation and Indoor Air, Washington, D.C. 20460, (202) 564-9235. [EPA Non-Ionizing Radiation Web Page] OSHA: The Occupational Safety and Health Administration's (OSHA) Health Response Team has been involved in studies related to occupational exposure to RF radiation. [http://www.osha.gov/sltc/radiation_nonionizing/index.html] NIOSH: The National Institute for Occupational Safety and Health (NIOSH) conducts research on RF-related safety issues in workplaces and recommends measures to protect worker health. Contact: NIOSH, Engineering and Physical Hazards Branch, Mail Stop R-5, 4676 Columbia Parkway, Cincinnati, Ohio 45226, or phone 1-513-841-4221. Tollfree public inquiries: 1-800-CDC-INFO (1-800-232-4636), or by email: cdcinfo@cdc.gov. Internet information on workplace RF safety: http://www.cdc.gov/niosh/topics/emf/#rffields. FCC: Questions regarding potential RF hazards from FCC-regulated transmitters can be directed to the Federal Communications Commission, Consumer & Governmental Affairs Bureau, 445 12th Street, S.W., Washington, D.C. 20554; Phone: 1-888-225-5322; E-mail: rfsafety@fcc.gov; or go to: www.fcc.gov/oet/rfsafety. International Commission on Non-Ionizing Radiation Protection (ICNIRP Europe): http://www.icnirp.de/