RF Sites: Safety
I wanted to take the time to discuss the topic of RF safety. Specifically in regards to transmission facility sites. First of all, I want to point out that, no... RF from normal radio frequencies will not give you cancer. However there are other health effects which various frequencies and power levels, can cause in humans. Such effects are Body Heating, and RF Burns and Shocks. These 2 issues are instant effects which have never been disputed. Body Heating can trigger other medical issues, such as asthma attacks, and heart issues, and may also produce headaches. This would only really happen fairly close to an antennas main beam, or in the case of an omni-directional antenna, fairly close to the antenna (how close is determined by the ERP - effective radiated power - of the antenna). RF Burns and Shocks can happen even if you are fairly far from a radiating antenna. Especially if you have metal fillings, or are wearing metal objects, in a high RF environment. RF Shocks are commonly described as a 'tingling' feeling, when this occurs. More serious RF Shocks and Burns happen when someone actually touches or gets very close to a radiating element. Such burns can be very severe and quite deep. and may require treatment in a burn center. Such burns have been known to kill people as well, both due to the severity of the damaged tissue, and/or the resulting infection of the tissue. Usually however, this is only concern with people who work in the field. Generally such a burn would not be encountered if you were simply standing in front of a dish, or antenna. You would likely have to actually make contact with an energized element in the transmission chain, and a very high powered transmitter at that! Other issues, are eye issues (cataracts), and a lower sperm count. These issues have been disputed, however they are widely accepted in the RF community as being fairly accurate. Both of these issues seem to only be a problem at higher frequencies... Roughly over 1 GHz at fairly high power levels. And they are generally a 'damage over time' effect, and not an instant effect. The general public will typically not be exposed to such levels of RF energy. That being said, there have been times - during my employment as an Engineer in the RF world - where I was at specific sites, which had high powered, onmi-directional, microwave transmission antennas. And I do recall getting an almost instant pain in my eyes when I looked at them. Other people in the field have also reported similar pains. Of course, you generally do not feel pain in your eyes. But the feeling of looking at those antennas, was like staring at the sun without any eye protection - although less severe. As for low sperm counts, well, I can vouch for that one as well. :P Lets move on to various sites. And discuss the various dangers and exposure risks at each site. Cell Sites: Cell Sites are very very common these days, and are likely the biggest cause in peoples concern over RF exposure. Generally, Cell towers are fairly safe to walk around, at ground level. The antennas most sites use are directional, and only put out about 100 watts or so (per channel), sometimes more, depending on the system. The RF Energy dissipates quickly as it moves away from the Antenna elements, and generally, at ground level, you would barely be exposed to anything more then what you would be if you were at home, or in your car. If you were to climb a Cell Tower, or be standing on a roof top next to the site / antennas, then you would be exposed to a lot more RF energy - likely more then would be considered safe. You likely will not be hurt or effected, if you were only that close for a short period of time. However the longer you expose yourself, the more in danger you are of feeling the effects. Over time, exposure levels at the base of a cell tower, may add up to enough to cause minor issues. I personally would not live directly under a cell tower for a period longer then 1 year. This is just a personal viewpoint however. Communications Towers: These days, Communications towers are more and more often looking like Cell Towers. As many companies move towards Trunked Radio Systems, to save costs, more and more Trunked Radio sites are going up... which can function similar to Cell phone sites in that they service 'cells' and generally operate many channels, in a small bandwidth of frequencies. In general, most Communications towers will be a lot taller then Cell towers, and thus their antennas will be even further from the ground. They generally only use about 200 watts of power, on average per channel. There is usually no problems at all with being near communications towers. at ground level, you are very unlikely to be exposed to any level of RF energy, which would be higher then considered safe and normal. Even living beside one for years is perfectly fine. Generally, communications towers are not operating 24/7, as they are used only when someone keys them up to talk. Broadcast Sites: Broadcast sites (AM, FM and TV) generally transmit at a fairly high power, and are likely the most likely place where a person would be exposed to RF energy which is above the recommended exposure limits. However in most (read 99%) of cases, all of these sites are fenced off, and have posted signs warning of said RF dangers. Sites which may not be fenced off in this manner, are sites on top of buildings, and sites in very rural and remote areas. In this case, they are usually not required to fence around the 'high exposure area'. AM sites offer an extra danger of RF Burns and Shocks, because many people do not realize that AM sites, usually energize the entire tower structure, which is isolated from ground. Many people have died, or been seriously injured when foolishly attempting to climb an AM tower for fun. Am sites can run anywhere from 500 Watts, to 250,000 Watts, however most are around 50,000 or 100,000 Watts. Another issue here, although minor, is Shocks from the high energy in the location of the AM site. Usually the towers will produce a field between 10 and 50 volts per meter (sometimes higher) in the general vicinity of the towers. This means if you were holding a piece of wire a meter long, you would be holding a 50 volt conductor, in essence, and likely you would feel it. You may also hear the radio station in your fillings, or 'taste' the electricity, as your fillings are energized. Loose change and keys can also give you small shocks. However generally the smaller the piece of metal, the smaller the charge. Other then this issue, and the issue of electronic interference on phone lines and other electronic devices, if you happen to live nearby, there are no serious long term health effects associated with living near an AM broadcast site. Even if you lived right at the site itself, the radio waves, since the wavelength is so large, do not get absorbed by the human body very easily. FM sites are slightly more dangerous to live near. VHF tends to get absorbed very well by the human body, and thus, you may exhibit health effects over time if you lived near an FM broadcast facility. That being said, most FM sites are not as powerful as AM sites or TV sites. But they are still often quite powerful. Anywhere from 500 Watts to 60,000 Watts for FM stations. Most FM antennas are high up at the top of a large tower, or on top of a large building. Exposure on the ground is likely not a factor. As is exposure to the antenna, for shock and burn hazards. You would likely have to climb up (even when its on top of a building) a tower structure of some sort, to even get close enough to the antenna to become burnt, heated, or shocked. TV sites are a lot more dangerous on average. They often operate between 1,000 Watts and 2,000,000 watts. And the Antenna location could be spread out using various antenna bays, up the entire length of a tower (i.e. not nessecairly right at the top). I personally often get 'RF Headaches' whenever I am near a TV tower. This is likely due to body heating. Depending on the frequency, the human body may be quite likely to absorb a great deal of the RF energy. I would not recommend living within 500 meters of a TV broadcast facility. TV can have a wide range of frequencies, ranging from very low VHF frequencies, to very high UHF frequencies. While these sites are usually fenced, the fences do not always protect you from the high exposure levels. Broadcast TV stations may be sited at the same tower as a broadcast FM station, or may share a tower with other TV stations, to produce even higher energy output. The bandwidth of TV signals is also a lot wider then AM or FM broadcast, in fact TV bandwidth is likely the widest transmission in the spectrum in common usage. While these sites are all routinely tested for compliance, it is important to note that in most cases, compliance means that the boundries where the public can access, are below levels of RF emissions which could cause issues, noticed right away, i.e. body heating. spending a long time (days, weeks, months, years) next to a TV tower, will likely cause other issues, which may be disputed as being caused by RF. There is a LOT of power coming out of TV stations, and while research is ongoing, it has not been conclusive on the effects of such energy on a human over time. Military and Research sites: These sites are generally multi-purpose with a variety of radio types and antenna types. Power can varry from 1 Watt to 6,000,000 Watts (for HAARP in Alaska). Generally such sites are located out of the way, and far from human habitation. Thus as long as you stay outside of the fences, you are likely never to be effected by any emissions from such sites. Aviation and Weather radars, if located near your home, may cause interference with your home electronics, and may over time cause health problems similar to those mentioned above in the FM tower site section. However since exposure is limited to a small burst every second or so, it will likely take a while before this has any effect on you. You are likely not going to receive health effects, if you do not have interference on your consumer electronic equipment from the radar / radio site. Aviation sites, for navigation aids for airports and airplanes are generally low powered, VHF frequencies, which are often directed upwards. Nav aids do not need to be powerful, because of the height of the aircraft intended to receive them. There is usually no issue of obstruction, or signal loss as the RF signal travels direct through the air to the airplane. You should not worry about such sites. Uplinks and Microwave links: Uplinks, are generally in the form of a parabolic dish aimed up towards a specific satellite in the sky. While Uplinks are generally high powered, their energy is directed in a beam projecting upwards. You are likely only to 'feel' this if you are very close to the front of the dish. Microwave links, are usually low powered, point to point systems, for voice, video, or data transmission. These are often used at remote tower sites, where it would be too expensive to run cabling to. These systems generally do not run more then 50 Watts, and usually have a range of 30 miles max. Standing in front of a microwave dish is generally not a good idea. not only are you exposing your self to microwave frequencies at a .. moderate power level .. but you are also likely blocking and interfering with the signal. lol Otherwise these systems are fairly safe to be around. That is about it really. I hope that has been somewhat helpful. Generally if you do not know a lot about RF, you should probably not go poking around at a tower site.