Jim, For an antenna producing a dipole-like radiation pattern you will need at least 3 dB of attenuation. If it has multiple lobes the ERP can exceed 10 mW in certain directions. Most DUTs will produce a dipole-like pattern with one or more lobes. The "GND" portion (case, PCB, etc.) opposite the whip antenna acts as the second half of a dipole with the whip being the first half.
If you attentuate the receiver path too you raise the receiver noise figure by 3 dB. Dave Cuthbert Linear Technology From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Jim Eichner Sent: Thursday, April 19, 2007 12:09 PM To: emc-p...@ieee.org Cc: Jim Eichner Subject: 0dBi antennas? We have a situation that has me scratching my head. An ISM-band wireless device that we are using has lowest output power setting of 10mW. We are trying to limit our power across the whole band to 10mW e.i.r.p so that we can obey the France 10mW restriction for outdoor use in channels 11-13. So we need a 0dBi whip antenna and we can't find one. I'm starting to wonder if the wireless device designers just plain got it wrong by not having a lower output power setting. Q1: My practical question is does anyone have a source they can point us to? We're looking specifically for a 0dBi whip antenna, articulated, terminated with a coax pigtail lead and a U.FL connector, but manufacturers can often customize terminations so the main parameters are 0dBi and whip. The search has led me to revisit the theory, in particular that antenna gain is really a measure of directionality and is related to the signal magnitude in the pointing direction, relative to that of an ideal isotropic radiator. Q2: My theory question is does a real life 0dBi antenna really exist? Isn't that an ideal isotropic radiator and therefore non-existent? Or are mfr's taking a directional antenna that has gain and adding (or designing in) attenuation to overcome the gain? Thanks in advance for any help and insight the forum can offer. Jim Eichner, P.Eng. Compliance Engineering Manager Xantrex Technology Inc. e-mail: jim.eich...@xantrex.com web: www.xantrex.com Any opinions expressed are those of my invisible but not isotropic friend. Confidentiality Notice: This email message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. - 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 emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com 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 emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
