Ken, I believe you are correct. There should be factors for this loop antenna from Emco that convert the raw reading (in dBuv) to a magnetic field level (like dBuA/m).
The spectrum analyzer does NOT read in dBuv/m as he seems to suggest, it only reads in dBuv or dBm, but some anaylzers do allow factors to be entered so the display will be in useful units. I prefer not having the analyzer apply factors. Less chance for errors that way, IMHO. Bob Richards, NCT. --- Ken Javor <[email protected]> wrote: > I may be reading this post wrong, but the -51.5 dB > factor is not an antenna > factor at all. It is the ratio of magnetic to > electric field intensity in a > plane wave. It is -20*log (377). The use of that > number is quite > approximate in the near field of the transmitter. > > From: Y W Leung <[email protected]> > Date: Thu, 23 Jun 2005 11:41:41 +0800 (CST) > To: [email protected] > Cc: [email protected] > Subject: ??? RE: ??? RE: Near field H-field > measurement. > > > Dear Dave, > > Thanks for your information. > > Since the local regulatory body set both E-Field AND > H-Field limit for > frequency range under 195kHz. But as I know, for all > radiated emission > measurement under 30MHz should use loop antenna, so > I use EMCO 6502 for E > and H- fields measurement. > > The spectrum analyzer dispaly (dBuV/m) with > transducer factors ( magnetic > antenna factor -51.5dB). For H-field, I used > extrapolation factor "3" to > calculate the corresponding limit at 10m ( becasue > the document states the > limits at 300m!) I used the reading on the spectrum > analyzer plus (-51.5dB) > then I can get the H-field value then I compare it > with the extrapolated > limit at 10m (measuring distance). > > For the E-field, I use the reading on the spectrum > analyzer and compare with > the limit at 10m (use the same extrapolation factor > "3" to determine from > 300m). > > Since theoretically, when the Tx & Rx antennas are > both loop antenna, within > the near field region, H field attenuate at the rate > of 1/(r^3) and E-field > attenuate at the rate of 1/ (r^2). > > My questions: > > I should use "2" or "3" for the calculation of > E-field extrapolation? > > The mesurement methods is valid or not? > > I also thanks to all experts replied the message of > this problem. > > Regards, > > Derek. > 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: Scott Douglas [email protected] Mike Cantwell [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
