Degaussing

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.