I don't disagree that the biconical and tuned dipole should give the same result if they are in the far field of the EUT. I am saying that at 30 MHz you are not in the far field and therefore I would expect to get different answers from each antenna. Just look at the angle subtended by the 5 meter dipole 3 meters from the EUT. A plane wave means that the radius of curvature of the field is so large that the wave-front impinging on the physical length of the antenna is plane, without curvature. That is hardly the case when the length of the antenna is longer than the radius of curvature.
---------- >From: Cortland Richmond <72146....@compuserve.com> >To: "am...@westin-emission.no" <am...@westin-emission.no>, ieee pstc list <emc-p...@ieee.org> >Subject: Re: E-field to voltage >Date: Wed, Sep 4, 2002, 10:48 AM > > > AMund, > > That's correct. One adds the antenna factor in dB to measured dBuv to get > the field. > > Ken Javor points out that you do need to worry about being in the > plane-wave, far-field. 5 dB dipole AF is typical of around 50 MHz, where a > three meter distance is enough to be in the far field - for a small EUT, > anyway. An EUT of appreciable size should be measured at 10 meters. > > Ken and I may disagree about antennas. I'd say that a properly calibrated > bicon SHOULD give the same result as a properly calibrated dipole, but > because dipole impedance varies more with height, you may be mislead by > what you read. For a horizontally polarized 50 MHz dipole between 4 meters > and 1 meter above ground, the radiation resistance may be anywhere between > about 60 and 100 ohms. This will affect its antenna factor. If both are > calibrated on a 3 meter site, over the heights from 1 to 4 meters, they > should give the same results. > > Cortland > > ------------------------------------------- > 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: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > 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://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > ------------------------------------------- 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: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com 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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
