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Hi, Tommy,

As to quarter-track 30 in/s playback, this is one of the reasons I have 
invested so much time and effort into the Sony APR line. They officially 
play 3.75 in/s to 30 in/s, although each head assembly is nominally only 
three speeds, but there is a DIP switch in the head assembly that allows 
you to select 3.75 to 15 or 7.5 to 30. That DIP switch also permits 
assignment to 12 different memories (some parameters are preset to 
certain memory locations, such as some are for half-inch tape, some are 
for timecode, some are for mono).

In any event, I could capture some of the 30 in/s material with either a 
quarter-track head if that was ideal or the 8-track, four-channel 
elevator head if we have to look for remaining swaths less than 43 mils 
in width.

As to B-wind, in instrumentation, the IRIG standard was written with 
tracks counting up from the baseplate with the heads essentially in a 
B-wind position due to a turn-around roller, although the tape is A-wind 
on the reels. That conveniently corresponds to the normal topology in 
audio of tracks being counted from the edge farthest from the baseplate 
and increasing as you get to the baseplate.

In both instances, track 1 is the same edge of the tape! Of course, that 
is really only useful in one instance, as the only common track format 
between audio and instrumentation is 1/4-inch 4-track. Everything else 
in instrumentation uses staggered heads (including 8-track 1/4-inch). In 
these cases, the tracks are split between odd and even heads in order to 
provide for greater shielding between tracks in the heads. This reduces 
the need for wide guardbands to accommodate inter-track shields in the 
head construction because, as far as the head is concerned, the adjacent 
tracks can be used for inter-track shielding within the head.

For example, in audio, four-track 1/2-inch track width is about 70 mils 
and in instrumentation, they put seven 50-mil tracks in the same real 
estate. For audio, only 56 % of the tape width is actively recorded; 
while for instrumentation, 70 % of the width is actively recorded. I 
think the general practice was to put elements that were critically 
related time-wise all on odd tracks or all on even tracks. The Mt. St. 
Helens seismic tapes I had recorded WWVB on one track and a locally 
generated IRIG code on another track and, if I recall correctly, one was 
odd and one was even. The displacement between the odd and even gaps is 
specified as 1.5000 inches and that is "baked in" to the machine 
manufacture.

Cheers,

Richard

On 2013-02-26 3:12 AM, Tommy Sj�berg wrote:
> Hi Henry (and Richard)
> I see a lot of re-used tapes that were never erased - just recorded over. Like Richard says, if the old recording is long enough to be intelligible, it can be saved. "Overwritten" and "Partially erased" would apply for the original program material, but I haven't heard any term for the material put "on top" of the original - perhaps "new recording"?
> I do come across half-track and full-track tapes that have been overwritten by quarter-track recordings. One of the worst cases, as far as playing back, are full-track 30 ips recordings overwritten by 1-7/8 ips quarter-track. That leaves, in essence, a 30 ips quarter-track recording, of which I know no suitable machines to play it with.
> Another thing I occasionally see are half-track recordings where the tracks are reversed, i.e. the left track is backwards and the right is forwards. I came across a possible clue the other day, where such a tape (from 1957) was wound oxide out. I suspect B-wind machines were "mirrored" as far as track placement goes?
>
> Regards,
> Tommy
>

-- 
Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada                             647 479 2800
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.