So if I am worried whether the 1 us pulse width can be sustained, and I don't know how to determine it analytically, my plan is as follows:
I put a wire probe in the room, run it to a spectrum analyzer tuned to the transmit frequency, put the analyzer in zero span mode with a 1 or 3 MHz bandwidth and look at the modulation waveform. If it is significantly longer than 1 us, I know my constructive interference path delays are smearing the modulation away. Comments yea or nay? And thanks for all comments so far! > From: John Woodgate <j...@jmwa.demon.co.uk> > Reply-To: John Woodgate <j...@jmwa.demon.co.uk> > Date: Sun, 27 Jul 2003 07:36:15 +0100 > To: emc-p...@majordomo.ieee.org > Subject: Re: pulse modulation in reverb chambers > > > I read in !emc-pstc that Ken Javor <ken.ja...@emccompliance.com> wrote > (in <bb48596e.36a1%ken.ja...@emccompliance.com>) about 'pulse modulation > in reverb chambers' on Sat, 26 Jul 2003: > >> What is the limitation on minimum pulse width in reverberation chambers? >> I expect it relates to room size, but does anyone have either a >> functional relation or a rough order of magnitude? Light travels 300 >> meters per microsecond, so I would think a 1 microsecond pulse width >> would work just fine, but nanosecond rise-times would be lost. > > Judging by what happens a million times slower in acoustics, I think 1 > microsecond could be quite a bit short. Obviously it depends on the size > of the chamber. If there is a paddle, it might be necessary to allow > several turns of it to establish a cyclically stable field pattern. > -- > Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk > Interested in professional sound reinforcement and distribution? Then go to > http://www.isce.org.uk > PLEASE do NOT copy news posts to me by E-MAIL! > > ------------------------------------------- > 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: emc_p...@symbol.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 > 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: emc_p...@symbol.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
