On Fri, 19 May 2006 08:50:55 +0100, Jim Lesurf
wrote:

In article , Don Pearce
wrote:

In article , Dave Plowman (News)
wrote:

The maximum theoretical HF frequency on replay is defined by the
head gap - the smaller the better. Double the speed of the replay
and the wavelength halves - thus removing the final octave. In
theory, at least.

[big snip]

JIm, as I remember the theory of recording, the gap size is not that
important,

... for *recording*....

because the remanent field in the tape is determined, not by
the entire gap, but the trailing edge of the gap as the tape leaves the
field. So the gap on the record head will typically be quite a bit wider
than the corresponding read head gap.

I agree - given the added words I include above. :-)

OK, I should have been more explicit, but recording was what I was
talking about.

However the points I was making were aimed at Dave's comments
(above) about *replay*. The gap size certainly matters for replay. But for
*replay*, changing the speed has no effect on the wavelength *which has
already been recorded*. Bear in mind that this arose from a discussion
about a situation where you might find you had to replay at a speed
different to that used for recording, and then process the output to
recover the desired result. In this context my understanding is that
changing the replay speed should produce no changes at all (due to head gap
size) in what can be recovered.

Slainte,

Jim

Quite - it is just a bit of geometry, after all.

d

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