Hi Dave and Net, Transmitting at 160m (1.8MHz) in an operating position with about 600V/m in my amateur radio stations (HB9CVQ/DK2VQ) would certainly make me search for a reduction method to lower the fields to less than 20 V/m. I tested this with 1 kW output and a calibrated field strength monitor (Narda Safety Test Systems) in CW-mode. Setup: Antenna G5RV , short dipole 2x15.4m, normally 9.85m 450 Ohm open wire feeder, at 160m extension with extra 17,5m 450 Ohm line, common mode choke (35dB) , 3.5m RG213, asymmetrical tuner, TL922, IC-761. All equipment is shielded and properly grounded (max. I CM < 10mA anywhere at 1kW-reference ground plane below equipment desk installed-open zoning concept). The antenna feed point is about 7m away with the feed line being perfectly in the symmetry plane of the ant. The end of the feed line is about 2m away from the operating position. With just the 9.85m feeder line and 15 uH inductance , about 30 cm diameter, open-no shield, real low loss inductors at the end, to tune the line on each side, I got 1.5 KV/m in the operating position-about 1,3m away only with 100W output on 1.85MHz! That made me worry to change very quickly. Efficiency of this new antenna system (additional extended feeder by 17.5m- coiled up on 40cm diameter) is naturally reduced over a full half wave dipole, but reasonable for the restricted space. In publicly accessible areas near the antenna (feed point 12m up and ends down to 9m height above ground) the E-field drops to about 1V/m at full legal 1kW level. By the way measuring very near a metallic surface can sometimes produce strange readings with E-field probes, better check the surface currents with a suitable probe. I hope these comments are useful
Diethard Hansen Best regards Dr. Diethard Hansen EES President, Principal Consultant, Trainer US Senior NARTE certif. EMC Eng. 001937NE EMC+Automotive+Telecom QM+techn. EA-Auditor Euro EMC SERVICE (EES) Dr.-Ing. D. Hansen POB 64, Bahnhofstr.39, CH-8965 Berikon 2, Switzerland, Swiss VAT (Mwst.)No.:323214 tel./fax: +41 566 33 73 81 German mobile phone: +49(0)1736015909 www.euro-emc-service.de <http://www.euro-emc-service.de> [email protected] <mailto:[email protected]> ( mailto:[email protected] <mailto:[email protected]> ) Consulting+Seminars+R&D-Projects Marketing+CE-Testing+ww.Audits From: [email protected] [mailto:[email protected]]On Behalf Of [email protected] Sent: Freitag, 19. November 2004 15:47 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
