Of magnetic interest?

[Tim Williams]

http://www.alcatel-lucent.com/bstj/vol08-1929/articles/bstj8-1-21.pdf

Bizarre... the B-H curve is referred to as "wasp waist". It goes back to
zero, and it doesn't take a straight line to get there by any means..

What you'd see in circuit: apply a square wave voltage and the dI/dt spikes
twice: once as it crosses zero current, again as it actually saturates.

Tim

 

[Fred Abse]

Wow. Did Bell Labs get their money's worth out of this guy or what???!!

Claude Elwood Shannon, and others, too.

 

[Fred Abse]

http://www.alcatel-lucent.com/bstj/vol08-1929/articles/bstj8-1-21.pdf

Bizarre... the B-H curve is referred to as "wasp waist". It goes back to
zero, and it doesn't take a straight line to get there by any means..

What you'd see in circuit: apply a square wave voltage and the dI/dt
spikes twice: once as it crosses zero current, again as it actually
saturates.

Interesting paper. I'd forgotten about Perminvar.

 

[David Lesher]

The Bell Labs archives are incredible resources. I went back and read
several of Nyquist's original papers a few years ago.

Ditto on other topics as well. Reading how they made
coast-to-coast 4 Ghz microwave work in 1951 with > 100
repeaters.....and S/S+N ratio good enough for both voice &
television....or buried coaxial cable the same route, with a
reapeater every two miles....

A friend brewed up an index <http://etler.com/docs/BSTJ/bstj.html>
Beware: habit forming...

 

[Fred Abse]

But, a FAE from one of the core vendors told me that he
has measured hour glass shapes in many of their cores, they just don't
publish that BH Curave shape, insteda replace with a 'normal' shape,
because nobody would believe it.

That's going to bite some poor sucker in the ass!

 

[josephkk]

Ditto on other topics as well. Reading how they made
coast-to-coast 4 Ghz microwave work in 1951 with > 100
repeaters.....and S/S+N ratio good enough for both voice &
television....or buried coaxial cable the same route, with a
reapeater every two miles....

A friend brewed up an index <http://etler.com/docs/BSTJ/bstj.html>
Beware: habit forming...

For some reason i thought that the microwave trick was by a competitor.I
think that he went on to help build Sprint / fiber optic backbones.

?-)

 

[[email protected]]

I had a friend who worked for Bell, and on that coaxial system. It
needed constant attention, and is the reason NTSC network TV was so bad.
The chroma level and phase could be adjusted at every point in the
system, and there was no VITS or VIR, so it was done to however the
operator liked it.

So that is the reason for NTSC = Not The Same Color or Not Twice the
Same Color

 

[David Lesher]

I had a friend who worked for Bell, and on that coaxial
system. It needed constant attention, and is the reason NTSC
network TV was so bad. The chroma level and phase could be
adjusted at every point in the system, and there was no VITS or
VIR, so it was done to however the operator liked it.

First, the 4Ghz TD2/3 & 6Ghz TH were the preferred transport for
NTSC. That started with the first SF->NYC coast to coast feed
in 1951, and continued until they lost that significant business
to birds. It was possible to run NTSC over L-carrier, but with
limitations.

The coax had no idea of concepts such as "chroma level" and thus
there was no way to diddle same. There was equalization; you can
read about it as follows.

The 1969 L4 system is described at
<http://www.alcatel-lucent.com/bstj/vol48-1969/articles/bstj48-4-819.pdf>
& <http://www.w4dex.com/BellLabsRecord.htm>; the improved L5 at
<http://www.alcatel-lucent.com/bstj/vol53-1974/articles/bstj53-10-1897.pdf>.
The L4 was the first solid-state system they deployed. There is an interesting outage detailed at
<http://www.alcatel-lucent.com/bstj/vol53-1974/articles/bstj53-9-1817.pdf>

They were desperate enough for bandwidth to actually trial a buried waveguide system.
<http://www.alcatel-lucent.com/bstj/vol56-1977/articles/bstj56-10-1825.pdf>
<http://long-lines.net/documents/WT4ad.html>Fortunately, fiber
optics arrived before they got too far.

 

[David Lesher]

Read about the 'White Alice' network some time. The first 'Over the
horizon' microwave network built for the military in Alaska.

White Alice was troposcatter; a different critter than 4/6/11Ghz
microwave. One of the last troposcatters around was Florida
City <-> Cuba. Bell South hated it because it was at 900 Mhz,
where they wanted to have cell phone $ervice.

 

[David Lesher]

They were desperate enough for bandwidth to actually trial a buried waveguide system.

Even worse, they build buildings at Ballard MO & Hillsboro for the field trial
<http://long-lines.net/places-routes/BallardMO/index.html> they never did...

 

[WoolyBully]

So that is the reason for NTSC = Not The Same Color or Not Twice the
Same Color

Idiot. It is "Never Twice Same Color".

 

[David Lesher]

Equalization affects both chroma level & phase. You never worked in
a TV studio, did you? The coax to the cameras had to be matched to
under 1/4" to prevent phase shift in the chroma circuits. The same
restrictions were used with equipment that was RGB on multiple coaxial
lines.

No Long-Lines transport was over "multiple coaxial cables" any
more than a viewer needed a red set of rabbit ears, a green one
& a blue one. (That said, L4/5 used "Coax 20" cable with 9 tubes
east, 9 west, & 2 hot-standby; L3 used Coax 8. In both cases,
each working tube was distinct from its neighbors.)

L3, the 1953 tube-type predecessor to L4 could carry TVS with some limits.

<http://www.alcatel-lucent.com/bstj/vol32-1953/articles/bstj32-4-781.pdf>
The L3 Coaxial System: Television Terminals
<http://www.alcatel-lucent.com/bstj/vol32-1953/articles/bstj32-4-915.pdf>

From someone who worked on same:

"they placed a vestigial sideband TV signal on a 4.1 MHz subcarrier in the
vacant bandwidth above telephone mastergroup one."

"The advantage of TV on {4 Ghz microwave} TD-2 {vs coax} was
that the IF could be bridged-off at any repeater along the route
without disturbing the through-path."

[The IF was 70 Mhz. Most microwave relay stations never went deeper than
that 70 Mhz; "main" stations were junctions where traffic was broken down
further and rerouted.]

 

[josephkk]

IIRC the buried microwave thing was corrugated waveguide, not coax.

Cheers

Phil Hobbs

It turns out that i was trying to remember MCI. The history on wikipedia
reads different today than that i remember.

?-)

 

[David Lesher]

You still don't get it. NTSC COLOR VIDEO WOULD BE CRAP AFTER ONE
HOP ON THAT VOICE BASED SYSTEM. THE RGB REFERENCE WAS VIDEO CABLING
INSIDE A TV STUDIO. Even as FM video, the errors are cumulative.

It was not "voice based" until you got down to the channel bank level.
(Here's a good write-on on such
<http://www.alcatel-lucent.com/bstj/vol41-1962/articles/bstj41-1-321.pdf>
for those interested.) When used for TVS, the previous link on
L3 TV ops is a good place to start reading.

And as a system, it was such "CRAP" that the networks paid LARGE
sums of money to Long-Lines on a daily business, for 25 plus
years. Now, that big a customer could have been making a stink,
demanding alternatives, and whatever else.....instead of just
paying. But the record does not support they did that.

Now there certainly downsides to Ma's 5+ decades-long focus
on FDM systems. One was, when DS1 over T1 starting really
rolling out in the mid-late 1060's; many transmission folks
at the operating companies {& LL as well, I'd bet..} resisted
such, since it was unfamiliar. A friend retired from such a
Transmission Engineering slot told stories of battles over
replacing N with T.