HOWEVER, if they are in a twisted pair configuration, any EMF produced ALSO gets cancelled immediately and on any and every pulse. That is the whole idea behind twisted pair. It isn't just for grouping.
That's the problem! Shielded audio cable is good for eliminating electrostatic interference, which is a common cause of audio noise. But, it does practically NOTHING to eliminate low-frequency magnetic (inductive) interference. And, a computer monitor is exactly a source of magnetic radiation at several frequencies. The horizontal sweep and the switching power supply frequencies can be shielded to some extent, but it is not really practical. The vertical sweep (50 - 100 Hz) can't be shielded without insane effort, so the only real way out is to eliminate its influence on the circuit. That's why professional audio types use balanced circuits for mikes and all sorts of other low-level signals.
in the presence of interference sources, clearly NOT true!
Forget this diameter stuff. Unless the cables were FEET in diameter, and almost all solid copper, they'd have NO effect on 60 Hz magnetic fields. These fields penetrate conductors.
If you can route long cables away from the source (the CRT is by FAR the worst offender) that is the simplest approach. If not, a pair of transformers and a balanced, shielded cable should also work. But, the TRANSFORMERS need to be shielded! Many cheap audio transformers are NOT magnetically shielded, just put in a pot-metal box. if they are near any power transformers or CRTs, they can make the problem WORSE! If you think a single wire stretched in space can pick up a signal, how bad would 10,000 turns of wire be?
Jon
Silly. Flux lines are not *ever* straight lines, and in reality, they are ever expanding "shells" that emanate outward from the source, so even "parallel" wires would likely garner EMF. Though they can and are of course oriented so that they are mostly aligned along a single axis, it is not a good practice to think that noise abatement can be achieved by simply aligning the conductor with the flux.
No shit.
May circuit card utilize shielded channels that are merely a PCB conductor trace over a ground plane layer with a low, narrow "can" placed along its length.
Since "cables" are typically meant for connection between larger hardware elements, they are also typically flexible, not rigid.
A rigid interconnection is usually not referred to as a cable, but it is not much more than a hard encapsulation of a cable.
So they are out there, they just are not called "cables" at that point.
Maybe an archaic CRT type does, but a modern (and cheap priced) LCD display does not. Why folks are still using CRTs is amazing. They cost about ten bucks a month more just to run them.
LCD backlight supplies can radiate a lot of junk. This is especially interesting in things like digital scopes and spectrum analyzers.
A scope probe held near the screen of my Tek TPS2024 shows 600 mV p-p spikes at 664 KHz. Other scopes drool lots of EMI from around the edges of the plastic box near the LCD.
John
The PS in a modern, large form factor LCD display (not a PC display) is a one piece item integrating the rail for the backlight and the rails for the LCD and video works all together in a single SMPS. Your PC LCD display, with its remotely mounted supply is a different story. There, the backlight power conversion is local to the backlight curtain. Any design with local power conversion for that will be noisy as the space budgeted for it usually will always mean a poor design and a lot of noise. A well made HV supply can pipe the voltage there with far less noise. With more space for the design, it ca be made very quiet. Space constraints cause engineer to cut corners in design.
That happens in a lot of industries. That is why some Americans stopped buying American cars. US car makers went to cutting cost of manufacture to boost profits and that cut in quality cost them. Less screws in the door panel and plastic in the wrong places, and poor plastic type choices, etc. Now, even though they are far better quality cars, those folks have not returned as customers, and still have misconceptions about what is in the market.
BUY AMERICAN CARS, Damnit!
Can you recommend an LCD which does 1920x1440 and costs < £400?
There seems to be a gap between reasonably-priced 1920x1200 displays (which isn't quite enough; even at 1440, I find that I need to hide all of the toolbars, taskbar etc to read PDFs comfortably) and overpriced (and oversized) 2560x1600 displays at >£900.
I have a 24" Soyo (1920 x 1200) that I've seen recently for $250. I bought mine 18mos. ago for $275.
We get them over here at about $400 to $450 at places like Fry's.com.
My current is only a 24, but it is also only 1920 x 1200. It is an envision. Got it for less than $300, but that was a sale.
I also would like one of the higher resolution 24" jobs, or maybe a
25".My dual setup is a 24" 1920x1200 Envision with a 46" 180p 120Hz Toshiba in an over-and-under fashion on a HUGE laboratory workbech/shelf/desk made from 2x2 hot rolled stock (the thick stuff) 2 keyboards slide out from under and the desk height as well as the shelf height are adjustable. The shelf posts are like
Sure we did - "you". Second person singular is "thou".
Only kidding. In Middle English we had a special letter, which looked like a "y" but with a dot above it. It was pronounced "th" and that is where the confusion started.
In modern Icelandic they still have two versions of "th" - one voiced as in "this", and one unvoiced as in "thin". The voiced one is written "th", but the unvoiced one uses a letter called thorn, which looks like a lower case p, but with the vertical stroke extended upwards.
So now you know....!
d
Do you know anything about electronics?
Unlikely, I guess.
John
Makes sense; thou = tu. Except that the French don't really have a practical 2nd plural either, since tu has restrictions.
You and y'all work great.
John
Standard English USED to have a second person SINGULAR, which was "thou." You was the the second person PLURAL but became used as singular due to either excessive politeness or widespread ignorance or something of that sort. Eventually, people couldn't stand the ambiguity, but instead of resurrecting the old thou, which everybody except readers of Shakespeare had forgotten how to use, they came up with new plural forms.
Where I used to live in Texas, y'all was nominal second person plural, inclusive and polite, very much like 2nd person plural in many other languages. It is often used to address single persons when one intends to convey friendliness or politeness or inclusion in a group. One uses the singular and definite you when you intend something very definite as to person, like: "Billy, you get in here right now and clean up your mess." or "I love you."
I guess he lives in Florida or Georgia.
Doesn't matter where he lives, he's AlwaysWrong. Kentucky isn't even in the Mid West.
What? Now we got a new asshole chiming in?
Yes, it is, you stupid f*ck. The KeithStain of Usenet is WrongAgainAsUsual. That is your permanent name, fucktard.
Oh, and looky there! It comes from The University of Kansas.
Not by standard usage. But from Florida, every state is north or west. Kentucky is both.
When these definitions got fixed, I don't know. It's weird to me that the entire midwest is east of the centerline of the continental US.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.