[AV Media Matters] Coercivity compared

[rohre@ARLUT.UTEXAS.EDU]

>From a collection of data sheets: Coercivities-
Grand Master Gold 499 Studio Mastering Tape:
Hci 360 Oe

Ampex 478 low print Mastering tape: Hci 390 Oe

Ampex 631 Hci 270 Oe---this is typical of all open reel Ampex
audio tapes of
that time, something from 270 to 390 Oe for coercivity.

Ampex 489 Digital Audio, (now ADAT) Hci 930 upper layer, 730
lower layer, both
in Oe.

Note 489 is 18.8 micometers, or  0.743 mil.  Used in digital
modes, it would
be harder to experience noticeable print through, but I think higher
coercivity should help as well.

The small format cassettes such as digital 8 and 4mm are much higher
than analog audio coercivity.

My 1997 guide did not have the data sheet for Quantegy 632, but
imagine it is an improved 631.  This was a spiral bound listing of
data sheets, and appears to be publication T35-704.