In terms of heating ( cooking ) 900Mhz is more efficient but its a question then of density of tissue , I understand that between 70-90Mhz the human body absorbs most energy and that first microwave ovens were designed around 450Mhz but 2.4 Ghz was an I.S.M. band so permitted limitless power.
The leakage in the average Microwave oven should be so small that you'd never hear it on a 2.4Ghz cell phone (i.e. 50Mhz off frequency) many offie type 2.4Ghz cordless phone use 900mw on the base unit and 200mw on the handset. I would suspect the field intensity that close to the head could be substantial. Ralph Cameron ----- Original Message ----- From: "Ken Javor" <ken.ja...@emccompliance.com> To: <emc-p...@ieee.org> Sent: Friday, April 20, 2001 5:40 PM Subject: 2. 4 GHz cordless telephone, question of general interest > > Someone on this forum likely knows the answer to this question... > > I was at Wal-Mart the other day and they had 2.4 GHz cordless phones on > clearance. My home cordless phones are 900 MHz. One is multiple channels, > the other is some kind of spread spectrum. 2.4 GHz is very close to 2450 > MHz, the microwave oven frequency that resonates with H2O molecules. Is 2.4 > GHz close enough to 2450 MHz to cause significantly more heating than 900 > MHz (in the human head adjacent to the head/handset antenna)? I realize > this is very low power relative to a cell phone, but I wonder if the issue > was ever addressed. Another way of asking this question is, what is the "Q" > of H20 resonance? If it is much better than 50, the problem is not > important. If it is 50 or less, then 2.4 GHz would transfer more energy to > head tissue than 900 MHz. One way of measuring this effect would be to time > how long it takes to raise the temperature of a beaker of water a set amount > at 2450 MHz, and then time how long it takes at 2400 MHz... > > But this all must have been done already... > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: pstc_ad...@garretson.org > Dave Heald davehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://www.rcic.com/ click on "Virtual Conference Hall," > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
