Apparently, the old monochrome television receivers suffered for this effect. The horizontal output tube would oscillate and the emission would be picked up at the RF input causing a speckled line, or "SNIVETs" in the raster. Placing a resistor in the grid circuit helped damp or kill the oscillation.
Anyone recall this effect? Ralph McDiarmid, AScT Compliance Engineering Group Xantrex Technology Inc. From: [email protected] [mailto:[email protected]] On Behalf Of John Woodgate Sent: October 20, 2004 9:23 AM To: [email protected] Subject: Re: ... And they wonder why we test...? In article <[email protected] pqcorp.net>, Conway, Patrick R (HOU) <[email protected]> writes >I was thinking less of individual units that fail in the field, and >more of the fact that simple, everyday, devices have the capability for >significant impact. In this case a television set in an apartment >building may interfere with the ability of a search-and-rescue team to >reach a survivor. This is why we do what we do. Vacuum incandescent lamps can oscillate strongly at VHF (50 MHz and above). It's called Barkhausen oscillation and depends on metal from the filament being deposited on the inside of the glass envelope, to act as an electron reflector. Works something like a klystron. Mains voltage vacuum lamps are rarely used these days, and the above is one of the reasons. -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [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 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/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Scott Douglas [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
