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
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
The Bell Labs archives are incredible resources. I went back and read several of Nyquist's original papers a few years ago.
Everything he did, he did to solve a problem with real equipment in the real world. Other people were working on the same problems and made many contributions too (I recently brushed up on Black's and Bode's original papers too.)
In every single case, Nyquist seems to have come up with a fundamental truth, or diagram, or criteria, that wasn't just applicable to feedback audio amps, or wasn't just applicable to telegraphy, or wasn't just applicable to multiplex carrier phone systems, or wasn't just applicable to long undersea cable runs, but also was fundamental part of information theory and control systems. He established criteria and diagrams and notation that absolutely permeate all aspects of how people today think about information.
Wow. Did Bell Labs get their money's worth out of this guy or what???!!
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Thanks for sharing that URL!
The 'hourglass' shape quickly appears in the PSpice Jiles-Atherton Model as you try to approximate a square hysteresis shape, which at first I didn't believe. 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.
Also, gives me an opportunity to comment, Bell had the strongest monopoly on the US , possibily ever in its history, yet from personal experience, Bell did not appreciably abuse that monopoly. Instead, provided the BEST full service ever to customers [phone doesn't work? replace it. Lines don't work? someone fixed it] and delved into basic science and physics contributing IP like never before [such as you posted here]. Yes, it was relatively costly to make long distance calls, etc etc. But at least to me, seemed like Bell provided something for this form of 'taxation', unlike other entities in existance today. It was like their high cost of communication was a tax, but the US received SERVICE, FUNCTION, and Intellectual Developments. a win-win proposition, that is now gone.
So, tell me again, today exactly WHAT does the US have to sell to justify the present standard of living?
Claude Elwood Shannon, and others, too.
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
Interesting paper. I'd forgotten about Perminvar.
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
My first job, after serving three years in the Army, and just graduating with a BSEE, was with Bell Labs. I was fortunate in knowing people like Nyquist, Shannon, Black, Pierce, et al. They were all willing to help a new arrival like myself.
I left Bell in 1951 to "head West" where the aviation companies were getting into electronics. I haven't regretted that decision, but have often wondered haw a career a Bell would have developed!
-- Virg Wall, P.E.
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 Beware: habit forming...
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Check out "The Idea Factory" by Jon Gertner ISBN 978-1-59420-328-2
It's good if you are into that kind of stuff. The personalities involved are interestingly weird.
-- Bill Sloman, Nijmegen
That's going to bite some poor sucker in the ass!
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
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.
Read about the 'White Alice' network some time. The first 'Over the horizon' microwave network built for the military in Alaska.
=46or 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.
?-)
IIRC the buried microwave thing was corrugated waveguide, not coax.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
Helicopter Ben?
So that is the reason for NTSC = Not The Same Color or Not Twice the Same Color :-)
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
& ; the improved L5 at . The L4 was the first solid-state system they deployed. There is an interesting outage detailed atThey were desperate enough for bandwidth to actually trial a buried waveguide system. Fortunately, fiber optics arrived before they got too far.
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
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.
-- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
system.
Even worse, they build buildings at Ballard MO & Hillsboro for the field trial they never did...
-- A host is a host from coast to snipped-for-privacy@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
Idiot. It is "Never Twice Same Color".
Yes. How often did you see crappy color produced at the TV station, compared to network?
Preferred, when available. Otherwise, it was routed through coax. Jerry was working for ATT when JFK was shot, and was a part of the crew thrown together in a few hours to jury rig the all network feed to cover the news & funeral. The video was crappy, because the system wasn't intended to feed so many loads at each switching center. Normally, the three networks had their own backup circuits for the microwave system, but it was faster to patch the feeds in the coaxial network.
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.
Interesting links, but totally irrelevant. That system can't handle video, and has horrible equalization. It is usable for narrow voice channels, but +/- 6dB variation in bandwidth is absolutely useless for video. The hardware for video was strictly designed for video.
I had a pair of GE built 6 GHz terminals I pulled from an Orlando TV station's old transmitter site, when I was moving their old transmitter to build another TV station. They had wanted to convert them to STL service, but they were as bad as the L4 specs. I ended up scrapping them for the several hundred pounds of extruded & sheet aluminum.
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