>-----Original Message----- >From: Gert Gremmen [mailto:[email protected]] >Sent: Thursday, August 22, 2002 1:06 PM >To: Bill Morse; 'Cortland Richmond'; ieee pstc list >Subject: RE: Emissions "quick test" > > > >The technique of temperature variation is that >sensible, that heating up the *enclosure* of >a small box by hand !!! will be easily audible , if >the beat is down to only a 100 hz. >Just tapping on the pcb will also be audible, not >to let alone the effect of a freezing spray ! >But you definitely need a BFO equipped (measuring) receiver. >A spectrum analyser is of no use here (grin). >This really is the fastest way of finding out the real >source of a interfering spectral line. > >Note also that the difference between data/adress lines >and R/W CE and Clcok emissions can easily be distinguished >by the notable AM modulation (rythme) and using the speaker of >your receiver it's easy to distinguish between >foreign sources, (radio tv amateur cellular) and even other >equipments (PC) in the neighbourhood. >I even can distinguish between multiple processors on a large system. >If your supply is not well stabilized, you will even hear the >100 (120) Hz hum on your spectral lines ! > >This technique in combination with >your own ears is truly sensitive in a quality point >of view: I have proposed in the past to use a measuring receiver >for debugging purposes: a mal functioning microprocessor >will definitely produce another sound then it's fully >functioning brothers/sisters. You may astonish your >collegues by fault debugging through walls !!! ;<)) > >Automated measuring systems are of no use outside >the shielded room for exactly the lack of distinction >between spectral lines, and those who work with >a spectrum analyser do not know what they are missing... > > >Gert Gremmen >ce-test, qualified testing
SNIP Some spectrum analyzers have a built-in speaker, and you can use this feature to monitor an emission. Although you may not get quite the clarity that a BFO can provide, you can usually detect a frequency shift by tuning to the slope of the emission and listening to the relative noise. If the emission shifts away from your frequency, then you will hear more background noise. If the emission shifts toward your frequency, you will hear either a quieting, or the modulation on the emission. For those of you who do not have a built-in speaker, just connect a cheap audio amplifier and speaker to the video output of your analyzer. BTW, audio provides a dramatic lab effect and should always be used during executive tours of your lab. Regards, Ed Ed Price [email protected] 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: [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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
