Resent without attachment - sorry forgot the firewall rejects GIF files. It was a graph that shows all of the differing compliance levels and they are as much as 60dBuV/m apart. If anyone wants it I can send it to their individual mailbox.
----- Original Message ----- From: "Iain Summers" <[email protected]> To: <[email protected]> Sent: Sunday, August 06, 2006 4:30 PM Subject: Re: Near field/Far field what is D. > Gents, thanks for all of the comments so far. > > Ken exactly as you have stated regarding how antenna factors are produced > is > one of the issues that I am trying to bring to the fore for powerline > telecommunications (PLT or BPL in the US). The current papers being > circulated are not that helpful to either those for or against PLT. > > The problem at present is that CISPR 22 (or its European derivative) does > not really deal with radiated emissions below 30MHz and in any case the > location of measurements is going to be in a housing estate which is not > well defined. Those that are trying to produce a standard are trying to > come > up with common acceptance limits for Radiated Emissions based upon > existing countries > standards. (see attached small gif file) > > The issues are that existing standards: > > A. Measure at different distances > B. Use different detectors > C. Measure different quantities, H, E (H converted to E assuming 377ohms) > > The common consensus appears to be that you measure with a loop and then > convert to E using 377ohms. The problem is that when these results are > published opponents argue that their services will be affected because > they > can extrapolate to a certain distance and their receivers are sensitive > enough to detect this extrapolated value. The HOWEVER as far as I am > concerned is that these values are so inaccurate initially that it is > futile > to try and make this case on a few fronts: > > A. field impedance is not 377ohms at 1 or 3 m (where most measurements > take > place) > B. the antenna calibrations may not have been completed at 1 or 3m > C. the attenuation with distance may not be 1/distance. > > I have measured C, I cannot control B and I am trying to get a feel for A, > hence my initial question about 2D^2/lambda. > > Ultimately I am going to conduct some subjective mutual interference > measurements to come up with some answers but not to 2 decimal places - > that's for sure. > > Regarding modelling I was intending to produce some NEC models myself of a > single dwelling but even a single ring main electrical circuit is > difficult > to model because its overall dimensions are large (64m^2 in my house) but > it > has 2 conductors lying about 5mm apart with an earth(in the UK) running > down > the centre. I am looking into it and will (with David Cuthbert's help) may > come up with an extremely idealised solution. I'd like to understand the > field changes for changing mains impedance which can be anything from 15 - > 200ohms according to research. > > Cheers, > Iain > > > > > - 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/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: Jim Bacher: [email protected] David Heald: [email protected] 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 ______________________________________________________________________
