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eHam Forums => Antenna Restrictions => Topic started by: KB3YLQ on April 07, 2013, 05:57:35 AM



Title: FCC seeks to reassess RF exposure limits
Post by: KB3YLQ on April 07, 2013, 05:57:35 AM
This should be interesting.

http://www.arrl.org/news/view/fcc-seeks-to-reassess-rf-exposure-limits?utm_medium=twitter&utm_source=twitterfeed

73,

Loren KB3YLQ


Title: RE: FCC seeks to reassess RF exposure limits
Post by: KG4RUL on April 07, 2013, 11:56:19 AM
So, how will they spin the rules to allow one to press a microwave transmitter against ones head for extended periods of time?  Can you fry me now?


Title: RE: FCC seeks to reassess RF exposure limits
Post by: KY6M on April 08, 2013, 11:49:04 AM
So, how will they spin the rules to allow one to press a microwave transmitter against ones head for extended periods of time?  Can you fry me now?

I pretty much said the same thing on the QRZ forum... I'm sure the cell phone industry makes the FCC more money then we do...


Title: RE: FCC seeks to reassess RF exposure limits
Post by: WA8FOZ on April 08, 2013, 09:06:17 PM
Quote
Quote from: KG4RUL on Yesterday at 11:56:19 AM
So, how will they spin the rules to allow one to press a microwave transmitter against ones head for extended periods of time?  Can you fry me now?

KA6MLE:
I pretty much said the same thing on the QRZ forum... I'm sure the cell phone industry makes the FCC more money then we do...
In point of fact, nobody makes the FCC any money. All license fees, forfeitures, and the like go directly to the Treasury ( the general fund). The FCC gets whatever Congress decides to appropriate to them.

Where the money goes is lobbying Congress, and most important of all, PACs. A race for a House seat costs at the very least $2 million. That means that a Representative has to raise $20,000 each week! In a competitive urban district, the amount can be many times that. And since the SCOTUS has decided that campaign contributions are free speech and cannot be limited, it is wide open for the big boys to invest billions to foster businesses worth many billions. The bottom line is still just that: money matters.

It is AMAZING that the ARRL, with budgets of a few hundred thousand dollars and no PAC, does as well as it does. We are up against some EXTREMELY big opponents. Far more powerful than RF exposure rules or gub'mint regulations. OSISI.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: W6RMK on April 08, 2013, 09:12:08 PM
This is fairly normal and not particularly unusual in the regulatory world. Any time there's a special case (e.g. an exemption for hams) one would ask whether you can do away with the special case (regulatory simplification and all).

Doing a decent RF safety evaluation isn't all that hard (it's a lot easier than learning CW). There's plenty of simple analysis that a ham can do that would assess the exposure, so the need for a "no analysis safe harbor" is sort of small.

There's also the "multiple transmitter" problem. The regulations require that if there is more than one transmitter, you need to do the analysis, not take the exemption.  And that's not just ham transmitters, the cell phone and the WiFi and the BT and everything else count too.  There's a "less than 5 percent" exception, but I would venture that the fields from the cellphone are comparable to, if not greater than, the typical fields from a HF or VHF antenna.

There's also this problem:"exempt transmitting antennas that are unusually close to people could potentially lead to non-compliant exposure levels"  

Pictures in QST of people running mobile VHF rigs or HF compact loops on picnic tables running 100W don't help things.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: K1CJS on April 12, 2013, 03:57:14 AM
I would venture to bet that there are more ham stations that don't have a hard copy analysis done where one is mandated than there are those that do have one done.  Once more, there are more ham stations that have tweaked their analysis they have done so it shows things are OK.  Regulations like this are essentially useless--unless, of course, you get investigated for something else and the authorities check for the analysis.

In any event, there have been transmitters with their antennas close to people--all sorts of people, not only hams--for many, many years.  There isn't one instance yet where it was proven that RF energy from HF, VHF and UHF have caused harm to a human being.  Yes, the cell phones are more problematic for many reasons, but for our most used frequencies, the RF that people are 'exposed' to is essentially harmless in all but an extremely few cases.  Added--And those few cases are with power levels way higher than we usually use.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: KH6DC on April 14, 2013, 12:09:03 PM
NEPA or National Environmental Policy Act???  You mean we have to get an Environmental Impact Statement (EIS) just to put up an antenna???  Looks like the FCC is becoming a puppet of the cellphone corporations being misguided by the almighty dollar.

I wonder the cell towers always will receive a Finding of No Significant Impact (FONSI) on their EIS's but ours (if implemented) will be scrutinized with a fine tooth comb.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: KD0REQ on April 16, 2013, 11:05:50 AM
the ARRL summary also indicated labelling and barriers are part of the review.  so if your next HT is wrapped with razor wire and has a diathermy warning sticker on it, it can both make you bleed and cure it.

probably add $500 to the cost of the radio.  but if you rig a plug to the antenna jack connecting that razor wire, should be good for another 3 dB.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: N0JI on April 30, 2013, 10:44:57 AM
Enjoy your hobbies while you can.  The times they are a changin'.......


Title: RE: FCC seeks to reassess RF exposure limits
Post by: ZENKI on May 20, 2013, 06:00:30 AM
Meanwhile they let  all the crap equipment from China onto the market that causes vast amount of interference.

Nobody has faith in any of the government bodies like the FCC anymore anywhere in the world. They dont have the high moral technical ground anymore.
The quicker government departments like the FCC dies and blows away  out of our lives the better off we will all be.

Government is disease like cancer that has no cure. If somebody can make money out of getting away with high levels of RF exposure they will let them do it.  Just look at how the bent the rules on BPL and  made the ARRL look like fools by changing the goal posts. They then prance around like they have some moral and technical competence. When lawyer engineers try and fool real engineers they lose all respect.  Its even worst when these government bodies sole
existence is to accommodate their political masters.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: KH6AQ on May 21, 2013, 05:48:15 AM
I see this paragraph as the most important:

“We appreciate that Amateur Radio operators are knowledgeable about the appropriate use of their equipment, such that separation distances are likely to be maintained to ensure compliance with our exposure limits,” the FCC said. “However, since the existing amateur exemptions are based only on transmitter power and do not consider separation distance or antenna gain, exempt transmitting antennas that are unusually close to people could potentially lead to non-compliant exposure levels.” The FCC said that a separation distance of at least 24 feet would meet its proposed exemption criteria, “considering a currently exempt 50 W transmitter at VHF in accord with Section 97.13(c) and assuming an antenna gain of 6 dBd.”

The present rules do not take into account the antenna near-field and so RF exposure grossly above the occupational limits is allowed. Ideally RF E and H fields would be measured with a calibrated instrument.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: KJ4VKC on June 30, 2013, 09:21:51 AM
What about the typical mobile user such as myself running on 50W VHF when we're having trouble working the repeater on lower power or seeing what we can work simplex? Under the current rules I don't have to evaluate, but the suggested example of 24 feet under the new example would be nowhere near possible in my compact car.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: W6RMK on July 01, 2013, 08:33:46 PM
What about the typical mobile user such as myself running on 50W VHF when we're having trouble working the repeater on lower power or seeing what we can work simplex? Under the current rules I don't have to evaluate, but the suggested example of 24 feet under the new example would be nowhere near possible in my compact car.

this is precisely the sort of situation that needs actual analysis and not a safe harbor. The "safe harbor" is the 24 feet.   In reality, given typical duty cycles, unless you're a real alligator, you're not going to bust the limits with the averaging factor considered, but you need to do the analysis to be sure.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: K1CJS on July 02, 2013, 04:49:31 AM
What about the typical mobile user such as myself running on 50W VHF when we're having trouble working the repeater on lower power or seeing what we can work simplex? Under the current rules I don't have to evaluate, but the suggested example of 24 feet under the new example would be nowhere near possible in my compact car.

Even with a compact car, there is little need to worry about VHF operation.  There has been extended VHF operation in cars for over fifty years--and UHF (400 mHz) for over thirty.  There hasn't been even one report of harm coming to a person from such useage.  The people using that radio equipment would have reported such things too--because those people are your local police and public safety people!

Police units have run 100 watts--and over--in mobile VHF transmitters since the fifties and sixties.  Larger cities have used the 400 mHz UHF transmitters for around thirty years.  Not one of those people has developed any sort of medical problems from such useage.  When you start to speak of cell phones and such, yes, there may be a problem because of the much higher frequencies in use, even at low power levels.  Think of this though--lower power microwave ovens still run 800 watts to cook food, and still have to take some time to do it.  Radio systems do not put out nearly that much power for the usual communications, and such communications usually don't take as long as cooking food in a microwave does.

The push for the assessing RF exposure limits are on because of the nature of litigation in this country now--something driven by lawyers, not scientists and engineers.  If it WERE up to the scientists and engineers, this reassessment wouldn't be done, simply because the scientists and engineers know that the current levels are more than adequate now.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: K1CJS on July 02, 2013, 04:54:22 AM
Don't get me wrong, I do not mean to say that you should not follow the regs, but if the current thinking keeps up, pretty soon we won't be able to do much at all--without having a lead lined full coverage suit on and filling out paperwork every time we transmit!   ::)


Title: RE: FCC seeks to reassess RF exposure limits
Post by: W6RMK on July 16, 2013, 09:35:33 PM
What about the typical mobile user such as myself running on 50W VHF when we're having trouble working the repeater on lower power or seeing what we can work simplex? Under the current rules I don't have to evaluate, but the suggested example of 24 feet under the new example would be nowhere near possible in my compact car.


The push for the assessing RF exposure limits are on because of the nature of litigation in this country now--something driven by lawyers, not scientists and engineers.  If it WERE up to the scientists and engineers, this reassessment wouldn't be done, simply because the scientists and engineers know that the current levels are more than adequate now.

As an engineer who does these sorts of analyses as part of my job, I think a bit of clarification is in order.  The issue here isn't the levels of RF exposure: as noted, they've got good scientific justification and epidemiology behind them.  It's whether the existing safe harbor that lets you avoid the analysis is appropriate. As noted in the FCC document, the safe harbor for VHF isn't particularly practical for a mobile installation.  You're a lot closer than 24 feet. So, under the current rules, you need to do an analysis.  For a lot of hams, the duty cycle averaging allowed will mean that even though you are only a few feet from the antenna, you're still under the maximum permissible exposure.

But you need to do the analysis to be sure.  If you're running something with high duty cycle (ATV repeater? APRS in some weird mode?) you need to deal with it appropriately.  If you're contesting from your car (where you tend to have higher than average duty cycle) or running JT65 moonbounce or something, maybe you bust the limit.  You don't know unless you do the analysis.

The whole near field exposure is another can of worms. I'd hate to depend on some sort of point source approximation to calculate fields for a backseat passenger in a car with a trunk lid mounted antenna. For OET Bulletin 65, they took some typical ham installations and measured/analyzed them in detail to formulate the safe harbor limits. Maybe the same needs to be done with sort of canonical 2m or 70cm mobile installations.


Title: RE: FCC seeks to reassess RF exposure limits
Post by: K1CJS on July 19, 2013, 04:58:42 AM
Lets get one thing straightened out.  Those so called 'limits' were enacted in the last decade or so.  Before that, there wasn't any need for limits since lawyers hadn't 'infected' everyone with their ideas of "If you get hurt--sue!"  The absolute worst thing our society did was to let lawyers advertize their services.

There wasn't any reported incidents of anyone getting hurt (outside of touching an antenna and getting shocked) by RF exposure, and there were people constantly exposed to the RF of VHF and UHF transmitters in vehicles--with antennas on the trunk lids or close to the operators of the transmitters.  Nobody got sick, nobody got themselves 'cooked', nobody got hurt!

It is totally ridiculous how RF exposure now has everyone up in arms--over a cellphone putting out less than a watt, or by radio tranmsmitters putting out 50 to 100 watts!  Broadcast stations put out thousands of watts at their transmitters.  Still nobody around those transmitters hurt!  Its totally ridiculous to think that people are now going to get hurt--when radio transmitters have been around for years and nobody was hurt then!


Title: RE: FCC seeks to reassess RF exposure limits
Post by: KH6AQ on July 19, 2013, 01:34:53 PM
RF exposure standards and limits are not new.

The first ANSI RF Exposure standard in the U.S. was issued in 1966 with a limit of 10 mW per square cm. These standards are now handled by the IEEE and are reviewed every few years. As knowledge of human physiology as it relates to RF exposure evolves it is appropriate that the standards evolve also.   


Title: RE: FCC seeks to reassess RF exposure limits
Post by: W6RMK on July 20, 2013, 08:19:44 AM
10mW/cm^2 is only at some frequencies in the VHF, low microwave area.  the exposure limit is higher at lower and higher frequencies because you don't absorb as much energy from the field.

The limits are, for the most part, based on heating effects and related to Specific Absorption Rate (SAR).. how many joules per gram or cc of tissue, and then relating that to a temperature rise and that in turn to biological damage due to the rise. The temperature at which tissue damage occurs is surprisingly low (a few degrees C above normal body temp of 37C.. if you're running a high fever, tissue is being damaged).

The most recent revision of IEEE C95.1 had substantial changes, not so much in the levels, but in the terminology.  It's no longer "controlled and uncontrolled" exposures, but Maximum Permissible Exposure (MPE) for occupational exposure, and an "action level" for the general public.  This is to harmonize it with other safety standards, including the ICNRP, used in other parts of the world.

There's also a lot of work on trying to understand and appropriately describe limits from localized sources (e.g. a cellphone held next to your head). Historically, the limits were sort of "you're in a uniform field of this intensity" or for localized sources (diathermy or electrocautery).  The problem is that this isn't a very good model: different parts of your body absorb differently, different parts of your body have different damage thresholds, and the incident energy is highly non uniform. That's why the limits for cellphones are not "radiated field" but are SAR, where you have to calculate or measure the actual energy absorbed (often using a RF similar phantom head with probes)


Note that the levels are, by design, conservative.  They're basically set at 1/10th of the lowest level at which any effect has been reported in the research literature.  And, remember, it's based on tissue damage as the effect.  One can damage tissue and it recovers, generally with no long term effects. So you could in some cases receive substantially over the limit, take the damage (which you might not even be aware of), and heal.  The real question is whether the "long term effects" are fully understood. Consider light sunburns: the tissue is slightly damaged, it recovers.  Do it a lot, though, and there's an increased incidence of skin cancer.

I'm not talking, here, about potential long term effects from low exposures (below the damage level). I don't think there are any, at least in a statistically measureable sense.  If my body got heated up slightly due to RF, how would that be distinguishable from me being out in the sun (an incident flux of 70 mW/cm^2) or running a fever?


there's also the disturbing issue of the studies showing increased incidence of gliomas (a type of benign brain lesion) in cellphone users.   While in general, I don't think there's any athermal effects from RF, I wouldn't be sleeping with my cellphone strapped to my head, either.