29 Apr
2014
29 Apr
'14
2:37 p.m.
On 4/29/2014 5:45 AM, Jerome H. Fine wrote:
I had a lot of the Nike Ajax tapes which were all the 10" diameter 1/2"
7 track tapes. We also had Magnasee. We had all sorts of magnetics up
to alnico magnets available and could not make a dent in the recorded
patterns on the tapes.
Other digital media, such as 1/4" recording tapes and 1/2" 9 track tapes
at 800 BPI from our mainframe were made completely "blank' or the same
flat pattern with Magnasee as the authority with all the erasure methods
we tried.
I found out about the thermal recording method from an engineer who
worked @ Panasonic in Irvine at their facility for loading pre-recorded
cassette tapes (audio). Had I known they were using the thermal method
I would have like to have tried erasing a pre-recorded cassette, but did
not know about that.
I don't know how the magical EMP field would have a different effect at
a distance, but don't know about that. I know we were doing a lot of
research at the time for a government lab which was related to radiation
and electronic effects, specifically to make systems resistant to EMP
effects and radiation exposure effects, so I wonder if EMP would be that
much of an issue. certainly in most consumer electronics it might be.
But as an electric field, not a magnetic one.
Jim
jim
Chuck Guzis
wrote:
Here's an interesting question: Will an EMP
kill a floppy? Since it
takes a very strong field to erase one, I'm inclined to think "no".
In place of a hobby (limited time per application) use
degausser from Radio Shack (are they still around?),
I used to used a discarded coil from a large loudspeaker
(the coil is a bit larger than my fist) to degauss TK50
tapes so that they could be re-initialized as a TK70.
That was quite successful. Since it was almost a
contact situation, almost the total field strength from
the coil would have been applied. I usually moved the
coil from side to side over the surface of the TK50
to produce the desired result.
Since the EMP field from a nuclear device would rarely
be closer than a hundred miles, even though the original
field strength would be millions of times greater than the
coil I was using, perhaps the field strength on the TK50
was as large or larger as an EMP pulse. Does anyone
have any specs on what the direct application of a coil
produces vs an EMP pulse at a distance?
At one point, I think I did use the coil to erase an 8"
RX02 floppy, but I can't remember any longer if that
was ever actually done. Since I would have used a
DSD 880/30 to re-format the 8" floppy after that,
there really was no need to degauss the 8" media
first.
Jerome Fine