Good detective work, which unfortunately required a major effort on your part in terms of having to pick up and move. Forget about the inconvenience, the issue you raise about the effect of the RF disturbances on humans is really far more alarming. Glad you were able to clear out of dodge.
I'd like to add some to the discussion on the biological effects of RF. 1. Way back in the early '70s I worked at Motorola Comm division; next door to my lab was one run by Dr. Quiriano Balzano. His expertise was (still is, I suppose) exactly that: biological effects of RF radiation. At the time, he was doing extensive research in a very direct way (very un-PC now!). He used lab rabbits, exposed to well-controlled RF fields over a wide range of frequencies VHF upwards) for long periods of time. He found that the most sensitive indication of damage were the rabbits' eyes; they would develop cataracts after a sufficiently long exposure to a sufficiently high field strength. He then measured the near-field strengths and spectra of the many types of hand-held equipment that Motorola manufactured and sold, and conducted a years-long study using several times the highest levels he measured. NONE of the test rabbits ever suffered any ill effects; the resulting paper was published, reviewed, etc. and was generally accepted as valid. No subsequent study has ever been conducted to that same level of detail and thorough ness!
2. There is a very large study group that has been voluntarily exposing themselves to RF field strengrths MUCH MUCH higher for MUCH MUCH longer than, for example cell phones (especially current technologies, which use very low transmitting power even in marginal areas). I refer to the 1 million+ or so radio amateurs (I am a Life Member of both the ARRL and the IEEE) around the world. While I am not aware of any organized scientific study of this group, from my personal observation I imagine hams are on average among the HEALTHIEST and longest-lived populations! I am quite surprised no one has ever thought about doing that study; I suspect that far too many of the possible researchers have axes to grind that might be blunted by its results!
I don't think you can say amateur radio operators are among the healthiest folks, not without a scientific epidemiology study. I've known hams who died from brain cancer and hams who are indeed in their 80's and are still on the air.
The FCC imposes fairly stringent exposure regulations on licensed commercial emitters of RF energy, broadcasters. License applications have to address how a facility prevents over exposure to the general public and to workers who might find themselves near radiating antennas on rooftops or towers. Radio Amateurs have to self certify that they've read the RF exposure rules and their ham stations are in compliance. My guess is many hams probably are not in compliance.
Cancer triggers are hard to pin down as so much of the biological response is governed by the genetic roulette wheel. Some folks, like my brother-in-law and his grandfather, chain smoke their entire lives and never acquire lung cancer while mere second hand smoke can be fatal to others. You also have to follow people for many years, maybe decades, as the carcinogenic affects can take a long time to manifest. Animal studies using mammals other than humans, for obvious ethical reasons, may not reliably model the human body's response except, maybe for thermal damage to corneas as in the rabbit studies previously mentioned.
SAR (specific absorption rate) depends upon RF wavelength, distance from the emitter, square law (reducing field strength by the square of the distance) and part of the body in the main lobe of the field. Resonance of the human body can enhance absorption.
Children, whose biological cellular activity is high due to growth may be more susceptable to genetic cellular damage than the adult population as a whole, yet they are becoming more and more long term users of cellular handsets. Cell phones can radiate their half watt of energy in very close proximity to the head measured in centimeters. If we were only concerned about easily quantifiable energy absorption as measured thermal affect in tissue, this might not translate as a significant exposure issue at least in the short term. Study of the thermodynamic response of the circulatory system and the body's own thermal regulation tends to negate any fear of thermal affects at these low energy levels. But the jury is still out about potential subtle interference with membranes and the biochemical dances taking place within living and dividing cells. Could a rather tiny addition to the electric fields or thermal gradient within the cell help trigger genetic accidents?
I know of folks who are very sensitive to RF. They actually get headaches and feel a bit sick when in the presence of fairly strong RF fields. Some can't use a cellular handset for more than minute or two at a time. Most of us are not sensitive to RF, good thing when it comes time for an MRI, but a few of my broadcast engineering collegues are. Have there been any studies done to attempt to pinpoint why?
In my post, I did point out that to my knowledge there has not been any study of hams re longevity or cancers; I think it could definitely be a worthwhile effort regardless of the results. I've been out of the RF business myself, professionally speaking, for MANY years (over 35; even the last few years I was with Motorola, I had "graduated" to system-level design), so I don't have any personal stake in this battle. I live in the Atlanta area, and right now, every night it seems the evening news is running yet another story about hysterical parents near-rioting over having cell towers anywhere near schools or residential areas. Last night, one of those stated that there were 159 existing cell towers within 4 miles of the one she was protesting about. The clear implication is "why do they need so many?" Cell sites are NOT cheap to erect OR maintain; this particular one would result in $4 million INCOME to the school district (badly needed) over the next 10 years. It's needed because of the CONSUMER DEMAND (strongly encouraged by the current US administration) for vast increases in broadband data infrastructure. The only way to do that is by cell-splitting (which incidentally REDUCES the radiated power from each cell site!); ergo, more cell sites and towers, covering the same geographic area. The only way to stop this would be to outlaw smartphones (a "modest proposal" of Swiftian dimensions)!
This is a needless pot-stirring (IMHO) by the technically-illiterate mass media. EVERYONE who does understand the technical issues involved needs to help educate the illiterati and the public to forestall this sort of "pitchforks and torches" activism before it results in a further shackling of our ability to IMPROVE our lives and lifestyles with advancing technology by ill-advised and misguided policies.
I have been a ham for 35 years. I've seen a lot of research. An epidemiological study of ham radio operators would have to take a whole lot of other extenuating circumstances in to the picture. Don't forget about the wonderful materials we use to make electronic components and what happens to them if they burn up. Don't forget that they often set up their stations in the basement, where radon is commonplace. Don't forget that this is often a very sedentary activity.
There are lots of reasons why you might find that ham radio operators may not be in the best of health, and none of them have anything to do with RF.
That said, knowledge of RF in general, is rapidly disappearing. Few people understand much about how the radio spectrum propagates, about impedance, about the practical limits to dynamic range and so many more very technical subjects.
Instead we have people who think they understand the time domain and they're reinventing all the frequency domain stuff to fit in those terms so that they can make software of the radio. I can hardly wait until the first of these people encounters a less than ideal amplifier and exclaims "I don't get it --I've got 18 bits of dynamic range!"
The beauty of the CDMA standards in use here in the US is that they don't make those pulsed transmissions that are so easily picked up by poorly shielded audio wiring. Another good thing is that while RF is more ubiquitous today, it generally runs less power because it only needs to get to the nearest network node. After that, some other networking takes over and routes it to the destination.
I sympathize with those who feel that RF is the cause of their weirdness. I should remind everyone that by definition, RF radiation is NON-IONIZING. Aside of heating effects, no-one has ever shown that RF radiation is dangerous to humans, plants, or animals despite nearly a century of research. I'm not saying that such an effect can not exist, but I have to point out that this electrosensitivity research, despite nearly a century of effort by many different people, has yet to produce any consistent and reproducible results.
RF radiation is called non ionizing as its energy level, based upon frequency (wavelength), cannot normally bump electrons from valence rings of atoms. Thus the chemical reaction effects are considered to be non existent. RF is part of the same electromagnetic spectrum as X-rays gamma rays and visible light. The real question is, are there rare circumstances where RF energy can cause other biological changes. And are those events frequent enough that they should be addressed. Probably not. But we do need long term studies to get results above the noise and decide once in for all if more or less caution is appropriate.
Remember it is only in the past few years that we're all being exposed long term to SHF wavelengths from our cell phones, cordless phones, WiFi AP's etc. Also, remember that with digital modulation the peak energy level is much higher than the average level. So, if we are not dealing with tissue thermal effects, the average level becomes irrelevent. Peak RF fields have to be treated differently. When I specify a test load for a digital RF signal I need to know not only the average power dissipation required but the peak RF level in that waveform. The peak results in higher voltage stress of the resistor. Dummy loads known to work well at CW power levels have failed over time when subject to digital RF energy of the same average power because the peaks provided significantly higher voltage.
Human activity always results in benefits and problems. Life is a tradeoff. If we are too careful as a species we'll never progress. If we are too cavaliere, we may end our reign on this planet way too soon.
I think one of the main problems in trying to have a meaningful discussion about the possible biological effects of RF or EMF is that there are so many different kinds of radiation/electromagnetic frequencies and they are apparently not at all the same in their potential for affecting living beings. Another problem, partially dependent on the first one, is that not all studies are created the same, making it difficult to compare their results. A third is that biological systems are extraordinarily complex, especially compared to machines, and are subject to huge amounts of variables.
And yet another problem is that the researchers who do these studies often don't understand the engineering side of the problem and the engineers don't understand the research side of the problem. I can remember reading about one study where the researchers ended up cooking their lab rats with relatively small levels of RF because they used far-field assumptions instead of near field equations for the antenna radiation patterns.
One approach worth considering is to assume antenna reciprocity with MRI images. This would give people some idea of how much of what frequencies of energy the human body would absorb most highly. Right now the radiation standards are pretty broad and are based upon some crude thermal assumptions, with a fudge factor thrown in for good measure.
We might do well to consider limiting exposure to those frequencies that are most highly absorbed by the human tissues. And while we're at it, examine whether it is feasible to allow exposure to greater amounts of radiation as long as those wavelengths are not easily absorbed human tissues.
Also, we make the assumption that pulsed power averaged over time won't hurt anything. However some parts of the body may not conduct heat away all that well (making the assumption that the heat conductivity of human tissues can be approximated by saline water may not be all that well founded)
I agree that there is still much that we can do to improve RF safety --but in the scheme of things that can hurt or kill people, I think other research deserves priority. If we studied everyday household chemicals with half as much fervor as people have about this stuff, why, I'm sure we could lengthen the average human life span by a whole year. (OK, I'm being a bit sarcastic here, but only a little).
Thanks, ab3a, for some good summaries of these issues.
However, there's a big difference between chemicals you can choose to buy or not to buy and bring into your home, and RF signals bathing your house, your car, and everywhere you go in a city without your consent. I think that's a large part of why those people are making so much noise.
I agree that the mass media often gets it wrong and contributes to mass hysteria about technology. Problem is when there are alleged experts with opposing opinions the unwashed have nowhere to turn as they do not have the expertise to research the answers for themselves. I put the blame squarely on the US education system both high school and college. Liberal arts majors should be exposed to life skills knowledge that incluse science and technology for the non technologist. And it should be a requirement, not an elective.
Ironically, those that protest cell tower placement increase their exposure to RF from their handsets by forcing them to put out more power to reach more distant cell sites. They do not understand the physics or the technology and thus make the wrong decisions regarding RF exposure concerns.
I would love to see a Sherlock or Monkeys which talks about something that took place in the 21st century. But I digress. My point here is that one can't help but notice that RFI has actually increased in recent years. My beloved Blackberry is among the biggest culprits. Who among us hasn't been on a conference call where asychronous (actually, often persistent) buzzing is disrupting the discussion. "Can everyone check if their Blackberry is near the phone?" is a common question on these calls. I don't know how designers can easily stanch this interference. It's not like you can put a choke on the antenna without killing the signal. Still, it's a serious problem.
The amount of RFI has definitely increased because there are so many more sources, both in terms of different kinds of wireless transmission technologies on various bands, such as WiFi and 4G networks, and in terms of point sources (millions of cell towers, millions of Blackberries and WiFi-equipped laptops) for each of these transmission technologies. Other, perhaps less obvious sources, include clock radios and halogen lamps.
But as a product designer that routinely sees thier device used in the situation you describe below, one would think that they would put in a brick wall RF filter that would shunt everything from about 800mhz and above.
Any first year EE student could design a passive filter that would do the job and it would cost all of $0.50 to implement. Unfortunately the 'consumer' electronics industry has a long history of paring down designs for cost reasons, typically resulting in degraded or poor performance of the product.
It is the 21st century and RFI susceptance as you properly point out is a real and continuing issue. And the problem will only get worse as more and more wireless devices are unleashed and cost pressures continue to drive designs towards minimalist levels.
As the RF spectrum becomes more and more crowded proper pre-selector filtation becomes more important, but it also becomes expensive. Very steep skirts are required to separate out services that abutt each other. And filters introduce their own amomlies, ripple, group delay, etc. Multi-pole cavity filters of the type used for microwave systems such as C-band satellite, are labor intensive as each pole has to be hand tuned during assembly. They are not cheap. The waveguide flanges, the semi rigid inter cavity coaxial cable links and the pickups on either end add to the cost.
You are protecting a wide band low noise amplifier and down converter. In the past 25 years the cost has dropped from $100,000 for a nitrogen cooled parametric amplifier to under $300 for very quiet room temperature LNA or LNB of better specs! Adding $600 for for a front end filter to a $300 LNB will not make your product competative in the marketplace even if it is better.
A long time ago I worked at an intstallation in a Mediterranean port. When a USN sixth fleet carrier was visiting the port, NOONE could watch television or listen to the radio - the inteference from the ship's search radar was just too much. Don't know why they operated the radar in port, but they did.
I grew up next to a US airbase - in the UK. In the late 70's / early eighties, there was a well known stretch of road adjacent to the air base along which cars had a habit of stalling - dead in their tracks and for no apparent reason. The emergency service crews - AA and the like (UK's equivalent of AAA) - had learnt that the best means fo starting a stalled car in that location was to push the car a few hundred yards down the road. The car would then start with no problems. The problem was sufficiently serious to warrant mention on the local news I recall.
In that cold war era the authorities denied all knowledge... plus, it only seemed to happen to what were then Japanese imports, so nobody seemed to worry much at the time. (Presumably Japan was using electronic ignition a few years before the homegrown competition).
I work in solid state lighting. It is amazing just how much equipment is available today with no FCC marks on it. There is bound to be fallout from that as its use spreads. I have one very widely used driver on my desk here today which comlpetely knocks out any fm radios within 20 feet of it. (But who uses those these days I guess??).
In the 60's and 70's when television was analogue broadcast and the receiving equipment still a work in prgress Joe Public knew all about interference. We can expect the same awareness to arise as the internet of things grows over the next decade and various day to day items stop working for no reason.
We will see jobs, legislation and associated corrective action on multiple fronts as a result.
Actually the age of digital modulation will make it much more difficult for the general public to detect or understand RFI. Digital with good error correction will work through some interference sufficient to make an analog signal annoyingly noisy. But at some point it will simply mute, poof! There will be no tell tale sound of the interference generator be it a fish tank heater or nearby radar antenna. Most folks will never know why their on the air (OTA) DTV reception is so unreliable and will simply give up.
Anicodally, I once got a call from an airport whose FAA C-band satellite receive dish was having sporadic interference. I suggested they add a flange mounted C-band bandpass filter similar to what I was using at a nearby public radio station to eliminate desense from the airport's own radar and aircraft altimeters.
Digital reception is not going to make the public more aware of RFI. On the contrary, it is interference from digital devices that makes analog modulation less and less useful! Listening range of AM radio has been severely diminished by the rising RF noise floor everywhere. And lets not forget the BPL fiasco, broadband Internet over unshielded power lines! Those of us whose amateur radio hobby is still mostly analog can attest at the threat of BPL, a solution looking for a problem and creating its own havoc along the way. Is the dollar mightier than the physics textbook? You cannot rewrite the laws of physics. But it seems you can buy your way around the laws of regulation.
In 1976, I was working on a low noise video amplifier for a large area CCD array to be used in astronomical observation. When measuring noise figure and bandwidth, I was plagued by a periodic noise burst that made the measurement impossible. I checked for sources around the lab and then around the house (lab located in the basement of a hillside home in Fairfax, Marin County, CA.)
Finally, I happend to glance out of the window at the fine view of Mount Tamalpais which we had and recalled the Air Force search radar at its peak. I could see the radar site (~7 miles away) through binoculars; the rep rate of the interference was what I would have expected from the rotation rate of the antenna. A small Faraday cage around the measurement setup took care of the radar interference.
#1) While designing HF & VHF transmitters in the 1960s & 1970s, a common practice to test the chassis for "hot spots" was to Scotch tape an NE-2H neon bulb to a long piece of tuning coil core stock and with the transmitter energized, move the bulb all around the chassis, not only in the immediate vicinity of the transmitting tube(s), but also in the "tank" circuit section. RF hot spots would make the bulb glow brightly. That was an indication of spurious & degenerative power in the equipment. Depending on the operating frequency range, designed power output, and other factors, a sheetmetal redesign may have been warranted.
#2) At the early stages of WW II, my father was in the U.S. Navy. His "MOS" was Aircraft Technician I, however his REAL "job" was to service & maintain the then top-secret RADAR facilities in support of the operations headquartered in Morocco. He was detached to a squadron of PB-Y aircraft, station in nearby Rabat. He died of pancreatic cancer @ age 59. I have often pondered WHY? His lifestyle was fairly exemplary in his daily routine. He was NEVER sick w/ any of the common contagious diseases that plague so many, especially during the winter months. He had NO physical ailments, and never needed to see a doctor, UNTIL he started to complain of back pain in August of the year he died. By November, he had been confirmed diagnosed, and was dead by Jan of the following year. In the early 1940s, RADAR waves were not as explicitly understood as they are now. Was his daily exposure to this radiation somehow a cause of terminal illness? I'm NOT a doctor, nor a research scientist. I just ponder this anomaly twice a year, on the anniversary of his birth & death!
Like another responder, I was on a military base in the south Pacific. The large - I mean large radars being developed - had a grounded screen around it. A tall fence that would shield the island from the radiation. After use, dead birds and such were cleaned up between the building and the fence. Microwaved on the fence or in the air. - Navy guys often talk about working on this or that antenna and getting warm. A tracker ship with 100' dishes on it cut doors in half as some were resonant.
Now for the "take back the skies" thought - I was flying a 2-M sail plane on the West Coast - and we would start loosing control of our wings in an area. The gas guys flew bi-planes and single wings - and often had the same issue. Then one day a guy drove out to our area - an old runway in the weeds - he was the IT manager of a graphics company - his Earth station (ftp over a satellite link) was dropping out when we flew in a region of his beam. We moved (sad for us) to a high school with permission - and wished the company would relocate, but never did.
I'm in a geezer rock band that plays 60s tunes using mostly vintage tube guitar amps and such. One of our members has a pretty high powered (no pun intended...) corporate communications job that calls for him to be chained to his Blackberry at all times, lest a far flung exec need some speechifying advice. It has happened more than once that his device will BZZZZT through all of our gear and PA while we are on stage (at midnight, our time!) and he must drop his tambourine and head for the bar to take the call.
A slew of announcements about new materials and design concepts for transportation have come out of several trade shows focusing on plastics, aircraft interiors, heavy trucks, and automotive engineering. A few more announcements have come independent of any trade shows, maybe just because it's spring.
Samsung's Galaxy line of smartphones used to fare quite well in the repairability department, but last year's flagship S5 model took a tumble, scoring a meh-inducing 5/10. Will the newly redesigned S6 lead us back into star-studded territory, or will we sink further into the depths of a repairability black hole?
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.