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![]() "Yuri Blanarovich" wrote in message ... Thierry wrote: We know that during the emission of a radiotelescope (rare, for tests or to send SETI msg, Hi!), the radiation can sterilize people working in the dish. Nonsense - we know nothing of the sort. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) No-nonsense, it is sense. RF exposure causes temporary sterility, kinda birth control. Too much RF can cook us. Yuri, K3BU.us First, let's agree on nomenclature; a radio telescope is a receiving device only, it is not an emitter. Feel free to coin a new term for a highly directional, high power emitter used for astronomical research. RF exposure can cause many things, from nothing sensible to boiling to carbonization to vaporization. It all depends on the RF power, the absorption and the time of exposure. Absorption is dependent on frequency and conductivity of the sample. Heating is dependent on the power, the absorption and the ability to transfer heat from the sample. For instance, 14 GHz exposure will result in most radiation reflecting off a human body; move the exposure to 2.4 GHz, and the effective depth of heating will be several inches into the tissues. Move down to 960 MHz, and you will get even deeper heating. (Consider why industrial microwave ovens are at 960 MHz.) Some body tissues are more exposed to RF, and, having only modest blood circulation, have a poor ability to transfer heat. Assuming you are male, those tissues at risk would include your earlobes, fingertips, nose, corneas, elbows, penis, scrotum, testicles and toes. Your earlobes, nose, fingers and scrotum have good circulation, so the blood cooling helps to protect them. Your toes are usually electrically close to the ground, and in a region of lower power density. Your penis is also well cooled and poorly exposed, unless RF exposure gives you a woodie. And who cares what happens to your elbows? So that leaves your corneas and testicles as the most vulnerable tissues. Canadian Safety Code 6 is a well-written document that will also teach you a lot about RF emissions, RF measurement and biological effects. It's limits are based on old ANSI C95.3-1991 work, which has been codified as IEEE STD C95.1-1999. The USA FCC also uses the IEEE standard. Both the IEEE and ANSI want to charge you for access, but Industry Canada courteously provides a free download at: http://www.hc-sc.gc.ca/hecs-sesc/ccrpb/pdf/99ehd237.pdf Thanks, Canada! So we see that RF can do essentially nothing, it can sterilize, it can cook, it can kill, and it can destroy. It's all a matter of power, frequency, target and time. Ed wb6wsn |
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