Iain: You are dealing with a complex situation, which does not have an easy answer, at least not one that is also valid. The near-field is especially complex (literally). Be aware that there are several ways to define the near-field which are in use, some more theoretically rigorous than others.
It is not unusual to consider a 1/d^2 rolloff of E field in the near field as an approximation. In the far-field, the rolloff is 1/d if free-space conditions apply. In more realistic situations, the roll-off is 1/d^n. Rather than continue,, I am pointing you to sources which may help you answer the question completely. A good deal of material on the radiation from PLC is already available, much of it on the web. A good starting point is the UK Radiocommunications Agency website at www.radio.gov.uk. Search for TWG (Technical Working Group) and you will find a final report on Compatibility of VDSL & PLT with Radio Services in the range 1.6 to 30 MHz. This has a vast amount of technical content on PLT - Power Line Telecommunications a.k.a. PLC, and in the US as BPL Broadband over Power Lines. You can also search on PLT, and you will find several further reports and documents. I believe MPT 1570 deals with measurement of radiation from power lines, and can be found at the RA website. There are also ETSI materials, as well as an ongoing US FCC inquiry which is loaded with comments back and forth. This is at http://www.fcc.gov/cgb/ecfs/ where you can search for 03-104. Regards, Jacob Z. Schanker, P.E. 65 Crandon Way Rochester, NY 14618 Tel: 585 442 3909 Fax: 585 442 2182 [email protected] ----- Original Message ----- From: "PLC Webmaster" <[email protected]> To: <[email protected]> Sent: Sunday, December 14, 2003 8:03 PM Subject: E-field drop off with distance (1-30MHz) I am currently researching the radiated emissions from High Frequency Power Line Communications (1-30MHz). I am trying to obtain information on how the e-field typically falls of with distance. I have read books that have made claims that this is anywhere in the rang 1/d to 1/5d. I am trying to make a statistical analysis to explain to those who claim that in the near field it is (1/d^2) which they derive >from an infitesimally small dipole. Does anyone know of any papers, experiments or actual EMC compliance measurements in the range 1-30MHz that I could use to make an analysis of the drop off rate. Thanks, Iain 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
