RF Safety

23 Apr

Several days ago a contributor to a small QRP  group of which I am a member made a provocative posting. He suggested that 25 watts of RF into a vertical antenna, ground mounted, was sufficient to violate RF Safety guidelines. Not being one to let an obvious troll go unchallenged, I googled the net for some of the abundant RF Safety calculators populating the net. I did not check the programming behind the on-line calculator. It was stated that it was initially programmed in Basic by (Dr. I think) Wayne Overbeck N6NB. In any event in my later trials I checked results against several calculators, one of which was sourced by the government.

Results? Sure enough, the 25 watt level is in violation of RF Safety Guidelines at both 21 Mhz and at 28 Mhz in an uncontrolled environment (i.e. not inside your fenced backyard) and if you are standing at a distance of 1 meter from the antenna! 25 watts! Wow. Who would have believed that?

After a couple of days I began thinking about cell phones. Since RF Safety is an issue at 30 Mhz why not 1 Gigahertz? I plugged the calculators with 1 Ghz, .001 Meter as the distance and all zeros for antenna gain and 300 mw as power. Finding your cell phones power output is a bit of a challenge. All the units have been mixed to make direct comparisons difficult. Cell phones are rated not in power output but in SAR units. This is a measure of how much of a cells power is absorbed into a human tissue. That does me no good with my experiment. I spent some time looking for generic output power levels and found a resource that suggested most modern cell phones output two common power levels. 300 mw and 600 mw. The old style bag phones could output as much as 3 watts. All that aside, I was only interested in 300 mw. That would be the minimum power output and if it fails it would be damning. At least in my mind.

I ran a cell at 300 mw output and with the governments own RF Safety calculator the cell phone failed. The calculator suggested a 300 mw level at 1 Ghz is not safe at distances normally used by cell users.

The cell industry is full of disclaimers and what I like to call- weasel words. Specifically, they claim this power level is non ionizing as opposed to ionizing. I dont know much about human physiology and what ionizing vs non ionizing means but I do know one thing. Cancer comes from oxidation of a cells DNA. Weather during mitosis or not, any oxidation (breakage) of a cells DNA chain is cause for concern. In an effort to mitigate my families risks I am immediately making them all aware of the risks. I am suggesting they use blue tooth ear pieces and if they don’t want earpieces than  only to text via cell. Personally, I have been around RF all of my life and so I am probably closer to the threshold than my kids ,so I am just going to turn off my cell service. Now I am wondering  how much power those 1200 Mhz walk around cordless phones put out? Or for grins how about those 5 watt 440 Mhz walkie talkies? I am not trying to be an alarmist. Just cautious and exorcise good judgment.

Thanks for reading my Blog. Best, Chas W7MAP/5

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Posted by on April 23, 2009 in Radio


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