Degaussing
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It takes alot more power to erase DV tapes than what Hand Held Radio Shack Bulk Tape Erasers can handle. Here's a chart showing the power needed to erase DV Tapes. (It takes 1700 Oersteds to erase DV tapes.) Coercivity is the property of a given magnetic pigment to resist changes in magnetic orientation or re-orientation (= "erasure"). It is defined by the level of the magnetic field needed for (re-)orientation, expressed in Oersted (Oe). The higher the coercivity, the higher the resistance of magnetic information to re-orientation (or erasure) by external magnetic fields. AUDIO Tapes Oersteds ================================== 350 Oersteds = 1/2", 1" and 2" 350 Oersteds = Cartridge 350 Oersteds = Sep.mag.35mm film 365 Oersteds = Voice logging reel 1/2", 1" 450 Oersteds = Compact cassette ferric (IEC Type I) 450 Oersteds = Compact cassette chrome (IEC Type II) 680 Oersteds = 1/4", 1/2" digital audio reel 745 Oersteds = 3/4" digital audio cassette 10/750 Oersteds = Pancake various 700 Oersteds = DCC 930 Oersteds = ADAT 1440 Oersteds = RDAT COMPUTER/Data Tapes Oersteds ================================== 300/700/1500 Oersteds = Floppy diskette 51/4",31/2" 550 Oersteds = PC,Mini, Hard disk 310 Oersteds = Main-frame Spool 1/2" 550/650 Oersteds = Cartridge 1500 Oersteds = TK50 etc. 700 Oersteds = DCRSI cassette 310 Oersteds = Reel 1/2", 1" 675/750 Oersteds = Cassette 1050/1500 Oersteds = 8mm/4mm 1440 Oersteds = DAT-R 550 Oersteds = Cartridge 3480, DC600A 1900 Oersteds = Digital backup cartridge VIDEO Tapes Oersteds ================================== 750 Oersteds = Reel 1"`B'and`C' format 300 Oersteds = 2" 675/750 Oersteds = VHS pancake 2100 Oersteds = Mirror master 675/700 Oersteds = Cassette VHS 710 Oersteds = Beta 1000 Oersteds = SVHS 1050/1500 Oersteds = Hi8 630 Oersteds = U-matic 745 Oersteds = U-matic SP 1700 Oersteds = Beta SP, MII 850 Oersteds = D-1 1700 Oersteds = D-2, D-3 Digital 1700 Oersteds = Digital Betacam, D5 Digital 1700 Oersteds = DV, DVC, DVCAM, DVC PRO SECURITY formats Oersteds ================================== 600 Oersteds = Credit card 600 Oersteds = Library ticket 600/3500 Oersteds = Rail/Air ticket 600 Oersteds = Hotel door lock (INFO FROM: <a href="http://www.weircliffe.co.uk/degaussi.htm">Weircliffe</a>) Here's something interesting: ============================== From: Art Munson <artmuns@tape.com> Subject: Degaussing, erasing and magnetism Date: Tue, 27 Aug 1996 11:58:42 -0500 (CDT) Degaussing, Erasing and Magnetism --------------------------------- A lot of folks have asked about degaussing (erasing) media and particularly DAT tapes, so here's some info you might find helpful. Gauss: A unit of measurement of magnetic flux density produced by a magnetic force (coils). Gauss is a measurement of coil strength. Oersted: A unit of magnetic intensity of a magnetic field in a vacuum. Oersted is a measurement applied to media. A 4mm DAT tape has a magnetic field strength of approximately 1500 oersteds. Coercivity: The amount of applied magnetic field (of opposite polarity) required to reduce magnetic induction to zero. The ease or difficulty by which magnetic media can be de-magnetized. A 4mm DAT tape is a high coercivity tape. So: 1.) The higher the oersted rating, the more energy needed to *properly* demagnetize it. 2.) In order to degauss (erase) a magnetic tape, a magnetic force (gauss) of 2 2/3 to 5 times greater than that of the media to be degaussed must be created. In other words to demagnetize a media of a given oersted rating, it will take 2 2/3 to 5 times the amount of energy. 3.) A 1500 oersted tape would need a magnetic field strength in the neighborhood of at least 3000 gauss in order to *properly* erase it. Hope this helps and thanks to David Partridge for his input. There is a hand held DAT degausser available, with an oersted rating of 2800, that lists for $169. Please give a call at 800-321-5738 if you are interested. Art * Cassette House * e-mail:artmuns@tape.com * DAT tape - CDR's - Cassettes * web page http://www.tape.com/ch * 800-321-5738 "I will use no track before its time" (INFO FROM: <a href="http://www.solorb.com/dat-heads/digests/V2.900/D921">DAT Digest</a>) ================================== Radio Shack's High Power Gauss Field is 800 oersteds. <a href="http://support.radioshack.com/support_video/doc14/14741.htm">Specs</a> ================================== So as you can see, degaussing DV tapes can be done with the right equipment. Let's see...to erase a DV tape of 1700 Oersteds I need a degausser that can handle 3400 Oersteds. Hmmm, The Radio Shack High Power Bulk Tape Eraser handles 800 Oersteds. No wonder it didn't work.