>-----Original Message----- >From: Mike Hopkins [mailto:michael.hopk...@thermo.com] >Sent: Monday, March 03, 2003 1:32 PM >To: 'John Woodgate'; emc-p...@majordomo.ieee.org >Subject: RE: RADIATED IMMUNITY REQUIREMENTS FOR EN61326 > > > >Sorry, but I must be missing something.... > >Transmitting antennas are designed to radiate power, and the >field strength >of any signal being radiated will be at it's highest close to the >antenna.... in fact, depending on frequency and distance, one >might even be >in the near field effects.... > >Antennas may be made directional, which results in power being >concentrated >in one direction, but if you're talking broadcast antennas, they are >generally omni-directional arrays that achieve gain by keeping fields >concentrated at low angles so power radiated towards the sky >is minimized. >Such antennas would clearly produce their highest levels of >radiation close >to the antenna structure itself; however, directly above or below the >antenna fields would be less. > >I cannot guess why the radiated levels for these frequencies >would be lower >than for other frequencies..... > >The only thing I can think of is that maybe it isn't expected >that one would >be close enough to a broadcast antenna at these frequencies >for it to be an >issue (antennas are mounted atop very tall buildings and >towers) -- on the >other hand, a piece of lab equipment or control equipment in a >process plant >could certainly be very close to other sources or radiation >from, say, 5W >walkies used by security personnel -- how much of a field can you get a >150MHz a foot from a 5W transmitter?? > >Mike Hopkins >Thermo KeyTek > >
Mike: About 10 V/M. Ed Ed Price ed.pr...@cubic.com Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis 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 Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
