RF Safety

[ke5wj]

When the RF safety rules were added to ham radio some years back, there was a flurry of information about making the safety audit. I presume most hams did and found out they passed without much effort. Since then the subject has gotten a lot less press, from what I've seen.

I recently got interested again, since I am forced to use an indoor antenna about 20 feet from my operating position. (After some checking and calculations, I found out that all is well, just as I thought.)

I'm wondering what other hams are doing to ensure safety and compliance in regards to RF safety. A large percentage of people I've personally chatted with really had done nothing. Some said they checked the guidelines a long time ago and then forgot about the subject. Others weren't concerned and didn't even seem to be aware of the rules. No mention of RF safety was made in ANY of the recent license exams, best I can tell.

Now, don't get me wrong. I firmly believe that in most ham shacks, dangers from HF RF are small to negligible. Of course VHF, UHF and microwaves are a separate issue and obviously warrants caution.

I'm just wondering what everyone is or has done in regards to the RF safety guidelines and mandatory audit.

[K9STH]

Here is the URL for the University of Texas r.f. safety calculator:

http://n5xu.ae.utexas.edu/cgi-bin/rfsafety.cgi

If you run the calculations for your particular installation, in the vast majority of cases, you will see that your installation definitely meets the specifications set forth by the Federal Government.

Glen, K9STH

[K1ZC]

RF safety questions are still on the exams although not in the format they used to be. I have recently gotten into the hobby and noticed while studying that some of the exam sites have images for RF safety tables and so on, but that none of the questions ever references those images. I assume they are artifacts from earlier tests where this topic was given more emphasis.

I did the prescribed audit when I returned to Ham radio 3 years or so ago. I found that all was pretty much common sence as related to basic survival instincts. ( Fire hot, no touch! ).

The new leagal limit of 1500 watts............Well, I have worked the world even at the bottom of the cycle and never had any more than 300 watts at my disposal! If antennas are the problem where power output is concerned, then a copy of a good antenna book is a must. Antennas are the key to good communication, not the size of your amp! Don't know why people insist on running a Kw to talk 100 mi. on 40m in the middle of the afternoon anyway. I can do it just as well with 25!

73 de Craig..........KCØGOA

[NN6EE]

Glen,

It really boogles the mind how much Man likes to mess around with his fellow Man, especially in this instance!!! Have you ever heard of ANY HAM OPERATOR getting Cancer from his use of any of his transmitters into whatever type of antenna used??? I never have once!!!
Now I can understand the concerns about high wattage transmissions like 10,000w OR BETTER, either on AM or FM, or maybe Microwave transmissions near a person's home running in excess of say 100w, then most people would be concerned about that, at UHF or HIGHER even a smaller amount of power with the antenna aimed at one's head or body could be BAD NEWS!!! But with the power limitations we HAMS are relegated to would probably cause no problems at VHF or LOWER!!! Of course if someone were CHEWING HIS ANTENNA while transmitting then SURE he'd have a problem and it would serve the DUMMIE RIGHT!!!

WHADDUYAH THINK??? http://www.qrz.com/iB_html/non-cgi/emoticons/confused.gif

Jim/nn6ee

[K1ZC]

Jim,

RF is a hazard (from heat) and there is no disputing that. At the same time, I will readily agree that your typical ham station does not pose an RF hazard unless you key up that brand new 1.5kW linear with your directional antenna pointed right at the next door neighbors, or if you have an attic antenna close to the living space. Ditto for HT's, keep the antenna pointed away from you head or, better yet, use a remote microphone and there is not much risk there either.

Still, there needs to be the education process in place so somebody DOES NOT fry the neighbors (personally, I would love to light up my neighbors, but that is a different topic http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif ). Once you know the risk is there, you will be more likely to whip out that calculator when upgrading your station. Similarly, if you know a little bit about RF safety and the neighbors do complain, you can educate them a little bit before you gently explain that the tower, ugly as it may be, is not going to be dismantled just cause they don't like it.

As for cancer, the jury is still out on that because the epidemiological studies take soooooo long to complete. I suspect the evidence for cellular damage from RF will be weak to non-existent. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

An excellent FCC RF Exposure website can be found at W2ENY Radio (http://www.geocities.com/w2eny)

I personally did my calculations on February 29, to commemorate just how stupid the requirement really is.

It's like a cheat sheet for a wiz test!

RM

in FULL Compliance with FCC RF BS rules at The Radio Fortress (BS = Burn Safety)

[K9STH]

Everyone should really go to the University of Texas site that I listed above. The explanation, etc., of r.f. radiation is simple, but informative.

It seems that in the "controlled" environment (the area that the amateur radio operator can control the movement of people) that the r.f. exposure is measured over a 6 minute period. If the transmission is for a full 6 minutes, then one of the "factors" is 100 percent. If transmissions total 3 minutes out of that 6 minute period, then the factor is 50 percent (etc.). For "uncontrolled" environment (your neighbor's house, for example), the transmissions are averaged over 30 minutes for the first factor. Therefore, if your transmitter is operating for a continuous 30 minutes then the factor is 100 percent. However, if you are transmitting only 15 minutes out a 30 minute period, then the factor is only 50 percent.

The effects of r.f. are calculated on AVERAGE power output. For CW the "average" power output is 40 percent of the PEP power. That is, if the "key down" power is 1500 watts, then the "average" power is 600 watts. For SSB the "average" power output is only 20 percent of the PEP power. For AM, digital, etc., the average power is 100 percent of the output. But, with AM, only 375 watts output carrier is allowed (to meet the 1500 watt PEP rule). Therefore, on AM the average power is 375 watts.

Thus, if you are operating a "two-way" QSO on 20 meters on SSB, and take 30 minutes for the QSO, your average power would be 1500 x 0.2 x 0.5 or 150 watts. If you were operating CW in the same 30 minute QSO, your average power would be 1500 x 0.4 x 0.5 or 300 watts. On AM it would be 375 x 1.0 x 0.5 or 187.5 watts. These figures need to be "plugged into" the calculations that are made from the web site.

If you do the calculations, you will see that one would have to be almost touching the antenna to get what might even be considered a radiation level that might be harmful. And then, only if the person was there for a long time (meaning hours).

When you hit the higher frequencies, especially the 2 GHz range, then things are different. The frequency of microwave ovens was chosen because it will cause water to boil the easiest. Also, I have been told by certain medical personnel (doctors) that the resonant frequency of the human cranium is somewhere around 2 GHz. This is also the frequencies chosen for the PCS (Sprint, etc.) mobile telephone service. If there were to be any chance of damage from r.f., I would think that the use of the PCS phones would be the most likely to cause problems. However, the e.r.p. of those devices is so small, that I very seriously doubt that any problems could ever be caused by PCS mobile or portable equipment. Base stations (repeaters) could be a different matter.

[NN6EE]

Glen,

By the way thanks for the URL for the TEXAS U. Website for RF Calcs!!!

I ran a whole bunch of scenarios and I'm within the permissible LIMITS on HF, and as far as VHF/UHF are concerned I don't run any major power anyway so that was also no problem!!! http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

Jim/nn6ee

[KB1GYQ]

hum? #Try running a cell phone through that calculator...

0.6W, 1.0dBi, 2.4GHz - uncontrolled, not safe until 0.46ft
3W -> 0.96ft

1.9GHZ - uncontrolled- same as above

0.6W, 1.0dBi, 800mhz - uncontrolled -> 0.61ft
3W -> 1.3ft

Cell phones are not safe with the antenna next to your head. (then again, neither are most HT, but most HAM's know not to stick the antenna against their head like many call phone users do)

[K9STH]

I haven't run the calculations on a cell phone. However, you should use the "controlled" circumstances since you are in control of the situation. Un-controlled is for those persons over which you have no control.

Glen, K9STH

[KB1GYQ]

"Controlled" is only for those who know what they're doing... since most cell phone users have no clue that it might be a bad idea to hold a transmitting antenna right next to their head, I used the "uncontrolled" specs.

[K9STH]

Did you take into account the 30 minute rule for non-controlled exposure? The vast majority of cellular telephone conversations do not last 30 minutes! Also, even the best antenna on the handheld phones is well over a 3 dB loss when compared with a "normal" quarter wave. However, the calculator only allows a minimum gain of 0 dBi (1 dB more than the "best" antenna can do)!

Assuming a 6 minute and a 3 minute conversation the following applies.

For 6 minutes: .15 feet for controlled, .27 feet for un-controlled The e.r.p. is .12 watts
For 3 minutes: .12 feet for controlled, .21 feet for un-controlled The e.r.p. is 0.06 watts

Assuming that the antenna is worse than 0 dB (- 7dBi) which is much more likely in practice, you have to calculate the effective e.r.p. which would be the average power reading reduced by a factor of 4).

For 6 minutes: 0.1 feet for controlled, .16 feet for un-controlled The e.r.p. is .03 watts
For 3 minutes: 0.09 feet for controlled, .13 feet for un-controlled The e.r.p. is 0.015 watts

On my particular Nokia cellphone, when held where I normally hold it, the antenna is definitely farther away from my head for both the controlled and un-controlled when the -7 dBi is used for both lengths of time. It is close when the 0 dBi is concerned.

However, the FCC and the Department of Health admit that the standards are well into the "conservative" range, probably by a factor of at least 10. Thus, the actual possibility of damage from a hand held cellular is much less than the possibility of a person being hit by a meteorite!

Back in the early 1970s, the Texas Department of Health tried to instigate some regulations concerning r.f. exposure. This was their intrepretation of some obscure sentence in one of the laws that had been passed during the 1930s. They were within less than 12 hours of starting enforcement of these new regulations (which were absurd - like having to have an audio signal of level of at least 120 dB sounded as well as flashing lights everytime any transmission was made, including mobile units!) when the amateur radio population "got through" to the governor and got the situation resolved. Had the regulations been enforced, the Health Department would have required a staff estimated to equal over four times the number of the entire employees that were employed by the State of Texas at that time. The director of the Health Department was quite aware of this fact. He was trying to build an empire!

Back before 1900, people were claiming all sorts of ills from electric lights. Signs were actually posted in hotels that had electric lights telling people that it was safe to use them. You can buy reproductions of these signs from various sources.

Frankly, I think that too many people are looking for a reason to eliminate cellular telephones. I agree that too many people misuse them. But, trying to curtail the use of cellular telephones by finding a loophole through questionable "medical" reasons is not the way.

Glen, K9STH

http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif I can see the headlines and TV commercials now:

SECOND-HAND RF KILLS! http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

All the former rusty footed hippys gone left wing inviro-natzis will love this! http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

73 de Craig..........KCØGOA http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif

[KB1GYQ]

I well understand that the standards are conservative when it come to actual physical damage, but as I posted to another thread to our ET hunter; I know someone who can sense low level microwave RF, she is not radio savvy (i.e. didn't know what band cell phones operate in) she was given a cell phone, and found through using it, that is make her woozy; the problem does not occur with the older 49mhz band home wireless phones. There is a side to EM exposure that we do not fully understand yet, and that is the effect of induced voltages on the nervous system. I suspect that it may be an individual thing, perhaps related in some way to epilepsy. The power levels are indeed low enough to not cook your brain; but there are high enough to to cause QRM in some people! Perhaps sticking a cell phone antenna in your ear will become the next form of "drug abuse" http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

[KG4RYT]

RADIO'S DON'T KILL PEOPLE. PEOPLE KILL PEOPLE.
http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif #http://www.qrz.com/iB_html/non-cgi/emoticons/wow.gif #http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif #http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif