Andy, I ran a NEC simulation to make some sense of this. This is too big of a reflector for NEC to handle so I made a large rhombic. The rhombic is 1 meter by 1/2 meter. The receive antenna is a dipole. I moved the dipole in from 80 meters 1/2 distance steps. Here is the dipole current normalized to 80 meters:
DX Sim 6dB/step 80 0dB 0dB 40 5.9dB 6dB 20 11.6dB 12dB 10 17.0dB 18dB 5 21.2dB 24dB 2.5 22.9dB 30dB At a distance of 10 meters the measured differs by 1 dB. Interesting results, to me, but they are crude, fast, and free. To better simulate the dish I would used a number of phased long boom Yagi-Uda antennas. Dave Cuthbert Micron Technology From: [email protected] [mailto:[email protected]] On Behalf Of Price, Andrew P (UK Basildon) Sent: Tuesday, April 27, 2004 3:10 AM To: IEEE EMC-PSTC E-mail Forum (E-mail) Subject: Near field/far field calculation Hi all, Can anyone help I am having problems calculating the near field/far field boundary for a 9GHz Antenna which has a length of 1035mm. Regards Andy Andrew Price Principal Development Engineer (EMC Specialist) BAE SYSTEMS Avionics A125 Christopher Martin Road Basildon, Essex SS14 3EL tel: +44 (0) 1268 883308 email: [email protected] ******************************************************************** This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. ******************************************************************** This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [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 EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [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
