But there is a very big difference between the two fields Mr. Cuthbert cites, aside from frequency. The cell phone field likely has a field impedance close to that of free space, because the antenna is a good match to the transmitter. Unless your tower is around 100' and operating as a base fed quarter-wave stub, you are likely using a tuning device to step up the output potential of your transmitter to more effectively drive a shorter stub radiator. The net effect is that in the very near field the ratio of electric to magnetic field is very much higher than 377 Ohms. The susceptibility effect of such a quasi-static electric field is very different than for a plane wave, especially if the EUT is surrounded by a shielding material, such as the human body, or any metallic shielding material one might choose to employ. A conclusion I would draw from this is that if it were deemed necessary to simulate the near field of an amateur radio site or an AM broadcast station, I would use an open-circuited parallel plate, as opposed to one loaded by 50 Ohms or other matching impedance.
From: [email protected] List-Post: [email protected] Date: Fri, 19 Nov 2004 07:46:59 -0700 To: <[email protected]>, <[email protected]> Subject: RE: Heart pacemakers - Vulnerability to EM I don't know what the standards call for but it is quite possible for a person to be subjected to an E-field exceeding 500 V/m very near to an amateur radio station. This is the field at my operating position when I am transmitting at 1.8 MHz. A cell phone held close to the body will cause a field, at the body, of over 30 V/m. Dave Cuthbert From: [email protected] mailto:[email protected]] On Behalf Of Israel Sent: Thursday, November 18, 2004 4:55 PM To: [email protected] Subject: Heart pacemakers - Vulnerability to EM Hi all Heart pacemakers may be vulnerable to Electro Magnetic energy. Has anyone idea about safe immunity levels ? about relevant standards regarding this matter ? Thanks ! ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
