A badly setup PAL receiver can give an awful crawling venetian blind effect, whereas a poor NTSC system with some form of "tint" control will provide a better picture. Mind, I never understood why the US changed the field and line frequencies away from whole numbers!!
Thankfully I never got to see a SECAM receiver! Even France ditched their SECAM transmissions in 2011.
-- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
Do you ever get anything right?
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
When you remember who Jason pimps, you'll understand why. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I have a delay line here; it looks like 7.5cm path length, in a glass wafer with reflections at the edges and some paint-like applied shapes that act as sonic walls. Ceramic piezo elements are glued onto one bevel-cut edge. The sonic path is probably 15 cm (there's a retroreflector at 7.5cm), which (speed-of-sound-in-glass = 0.56 cm/us) makes it about 8 us. Probably the 'glass' is special stuff (leaded?). Size 2 x 3 cm. It scales with the area of the glass, so my south window at 90 x 180 cm would provide a delay of 26 milliseconds.
I'd say you're right, milliseconds that way AREN'T cheap. The audio effects folk use loosely held coil springs, and I've seen dollar-store toy microphones on that principle, which do qualify as affordable. For seconds of delay time, you'd need to buy lots of Slinkies and connect 'em in series.
Of course, you'd have a heck of a time keeping a coherent "beam" bounce through it -- a lot like a hall of mirrors, each time it penetrates another pane, it gets greener, dimmer and blurrier.
Speaking of photonic analogy, it's probably not infeasible to construct a coherent acoustic emitter (a phonon Yagi antenna..?). So at least you can then sort of reasonable path density without getting so much crosstalk between echoes.
Downside to the coil methods, they're dispersive. Torsional (in the wire and in the helix) and axial compression modes interact. Perfect example: have you ever listened to a Slinky when tapping one end? It makes a "djew! djew!" sound -- suspiciously like the blasters in Star Wars. Which is exactly what they used! (According to one show I remember..)
Echoes kind of do that anyway, so it's fine for musical purposes. For good clean waveforms... how big of a roll of fiber optic cable would it take to get a few seconds?
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
The speed of light is 299,792,458 metres per second in vacuum, about 200,000 kilometres per second in glass. That's five times around the equator.
The maximum spacing between repeaters in fibre-optic cables was less than 200 km when I was last interested, so anything more than a millisecond is unlikely to be practical.
You can make electromagnetic delay lines where the propagation delay is slower
patentimages.storage.googleapis.com/pdfs/US2854639.pdf
describes a cable offering 50nsec per foot, where regular coax is closer to
1.5 nsec per foot. It's tricky to make, but the cable is well behaved up to about 100MHz. You'd still need some 4000 miles of it for a one second delay - roughly two trans-Atlantic cable's worth.-- Bill Sloman, Sydney
I don't understand why he's even here. The NTSC moved the two frequencies because there was no way to eliminate color crawl if they didn't. It's all in their old documents. I've seen them from the fight over different systems for monochrome, then the various proposed color systems. I'm surprised that Europe didn't use the spinning disk system, as backwards as they are. Even as close packed as their countries are, they couldn't agree to any one kludge.
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
wire
example:
Which
To get that much delay would take about 200,000 km (5 trips around the earth?). That means about 6,000 regeneration stations, which will add about as much delay themselves. Moon bounce or satellite ring around the planet would do better in many ways.
?-)
wikipedia: NTSC - History
. To reduce the visibility of interference between the chrominance . signal and FM sound carrier required a slight reduction of the frame . rate from 30 frames per second to 30/1.001 (approximately 29.97) . frames per second, and changing the line frequency from 15,750 Hz to . 15,750/1.001 Hz (approximately 15,734.26 Hz).
So, the frame rate was reduced by 30/1001 Hz.
Presumably if they'd originally specified a chrominance frequency that was 30/1001 Hz higher it'd have had the same effect.
--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---
Presumably? You're as clueless as ever. As usual, Wikipedia glosses over important details. There was no chroma frequency that worked with
15,750 Hz and 60 Hz. It was all detailed in the proceedings before they accepted the new color standard. Do the math for yourself, including the fact that the video was interlaced to reduce flicker. They were working from a clean slate as far as a color standard, but to be compatible with existing monochrome sets, they had no other choice. Stop putting your foot in your mouth and do some real research. I've read the proceedings of the NTSC hearings on color. They were in the archives at the old Crosley plant in Cincinnati, Ohio when I worked for Cincinnati Electronics.-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
We had that some 30 years ago. I worked on an ECL array processor (a DSP chip in a double wide rack cabinet) with a buried "omega" layer for the termination resistors. Worked just fine except for the 16 layers, lol! Seems it was both expensive and unreliable. But we managed to ship a couple hundred machines out the door.
-- Rick
there's lots of informtion there but nothing I can actually use.
-- umop apisdn --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
If you consider only single-mode fiber, you can use a length four times: outgoing right circular polarization, returning (reflected) left circular, then do some magic and reinject outgoing left circular, return will be right circular. Speed of light in the waveguide is maybe half of speed in a vacuum, so you can get two seconds with one quarter light-second of fiber. That's just two turns around the equator!
Considered as a delay-line memory, it holds something near a terabit after you apply DWDM and other tricks... so you can make a similar delay with about that much disk space (if you have disks that can dump all their data inside two seconds, while reading input at the same rate).
They did have a choice but decided to compromise with a bodge. There was no clean slate! An explanation might have been more informative than saying the explanation is in some obscure archive.
With 15,750 Hz and 60 Hz required a colour subcarrier that created a visible beat with the sound carrier of 5.5MHz.
So engineers moved the mountain so to speak and shifted the frame rate by 1% to use a subcarrier frequency that didn't leave any sound carrier beat artefact.
Presumably there was sufficient equipment in use at the time such that the sound carrier was considered immoveable, which was a great shame as receivers would have coped with a minor shift in sound carrier.
Of course the demise of NTSC has made things much easier in not having to drop fields/frames and having meaningless frame timecode/counters.
-- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
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.