Sharpness

[lnx64]

On my old TV's, there is no sharpness control. Instead, I can use the fine tuning adjustment to slightly detune and it appears to act like a sharpness adjustment before loosing a good tuned in picture.

Is it ok to do this or is there a better way to sharpen the picture a little?

[kx250rider]

Usually on all-tube sets, replacing the video detector tube (or germanium 3-legged diode), and any caps in the video detector and video output stages, will sharpen it up a little. But honestly, the video response is never going to be as sharp as later sets, in most cases.

Charles

[wa2ise]

Old color TV sets used a "notch filter" to separate the chroma subcarrier from the luma (black and white) video. In the 80s sets started to use comb filters to do that, and allowed more resolution from the luma thru. But you'd see crawling dots on color transitions, and you'd see large regions of crawling checkerboard patterns on colored areas if the set had no filtering. The notch filter would remove pretty much everything in the luma above 3 MHz, and that's the missing sharpness. I used to work for RCA doing better chroma luma separators in the 80s.

[lnx64]

Originally Posted by wa2ise

Old color TV sets used a "notch filter" to separate the chroma subcarrier from the luma (black and white) video. In the 80s sets started to use comb filters to do that, and allowed more resolution from the luma thru. But you'd see crawling dots on color transitions, and you'd see large regions of crawling checkerboard patterns on colored areas if the set had no filtering. The notch filter would remove pretty much everything in the luma above 3 MHz, and that's the missing sharpness. I used to work for RCA doing better chroma luma separators in the 80s.

I'm going to judge, that based on this kind of picture mine produces, it's going to be a comb filter due to the dot crawl it has.

[lnx64]

In this picture, in a greyscale screen from my VCR's setup screen, the greyscale is pretty crisp. Though the white on blue text above is a tad fuzzy.

http://img.photobucket.com/albums/v3...ragon/year.jpg

EDIT: You know, I've never noticed this before, but I know this TV has an inline tube, but by this picture, it's shadow mask would make you believe it's a delta gun. That's odd, it's not a slot mask. :/

[ChrisW6ATV]

The "sharpness" control on newer color TV sets was never able to increase the resolution of a set, but only to boost the perceived detail, by increasing the high-frequency gain in the video amplifier. Generally, it should be set to 25% from the lowest setting or lower, to avoid "edge enhancement"/ringing on high-contrast changes in video content.

[old_tv_nut]

Originally Posted by lnx64

I'm going to judge, that based on this kind of picture mine produces, it's going to be a comb filter due to the dot crawl it has.

Nope, it's the other way. Crawl on vertical edges (horizontal transitions) like that vertical blue pole comes from a notch filter.

Crawl on horizontal edges comes from a comb filter, especially one that does not have a sophisticated circuit to detect the crawl condition and switch on a notch filter when necessary on that scan line.

[lnx64]

What I was getting at in the original post though, was that when using the fine tuning dial on the TV, I could get a perceived sharpness increase by tuning the dial slightly off tune.. It seems to sharpen it a little detail but does add a little bit of ringing.. The AFT button seems to favor the softer picture.

[old_tv_nut]

Originally Posted by lnx64

What I was getting at in the original post though, was that when using the fine tuning dial on the TV, I could get a perceived sharpness increase by tuning the dial slightly off tune.. It seems to sharpen it a little detail but does add a little bit of ringing.. The AFT button seems to favor the softer picture.

This is expected because you are running the carrier down the IF slope and making the higher video frequencies stronger by comparison.

[Jeffhs]

Originally Posted by old_tv_nut

Nope, it's the other way. Crawl on vertical edges (horizontal transitions) like that vertical blue pole comes from a notch filter.

Crawl on horizontal edges comes from a comb filter, especially one that does not have a sophisticated circuit to detect the crawl condition and switch on a notch filter when necessary on that scan line.

My Insignia flat screen (built in May 2011) has a 3Dy/c comb filter, but I haven't yet noticed any artifacts in its picture such as you mention. Perhaps by the time they started using comb filters in flat TVs, the cause of the "crawl" problem had been identified and remedied; that, or else my set has the required circuitry to cut in a notch filter if and/or when necessary.

[wa2ise]

Originally Posted by Jeffhs

...or else my set has the required circuitry to cut in a notch filter if and/or when necessary.

Back in the 80's when I worked at RCA (when it was a real company) I invented a patent doing essentially just that.

http://pw2.netcom.com/~wa2ise/radios/patents.htm specifically #4,656,501

[lnx64]

Too bad I can't view the images on the patent. :/ I was interested in it, but it loads up blank on my computer.

[lnx64]

I wanted to bring up the topic of notch and comb filters.

I found that my Sony PVM monitor, the prop in the X-Files earlier seasons, doesn't appear to use ANY filter.. There's dot crawl in horizontal AND vertical areas, and sometimes even just flat out "in" a color.

Wonder why a PVM wouldn't have any filter at all.

[Eric H]

My Sony XBR built in Dec 89 had a Notch Filter, also a Comb filter if I recall.

the Notch Filter was very effective and I left it on most always.
It would remove the sawtooth from the edge of diagonal lines very effectively without compromising sharpness.

the thing I didn't like was the SRS Sound, it was supposed to expand the sound, but mostly it made it sound like it was coming from the bottom of a barrel, I was never sure if it was the Circuit doing that or the Broadcasters not implementing Stereo properly.

[Jeffhs]

Originally Posted by Eric H

My Sony XBR built in Dec 89 had a Notch Filter, also a Comb filter if I recall.

the Notch Filter was very effective and I left it on most always.
It would remove the sawtooth from the edge of diagonal lines very effectively without compromising sharpness.

the thing I didn't like was the SRS Sound, it was supposed to expand the sound, but mostly it made it sound like it was coming from the bottom of a barrel, I was never sure if it was the Circuit doing that or the Broadcasters not implementing Stereo properly.

My 19" Insignia flat TV has the 3Dy/c comb filter, which works quite well. This is the first TV I've ever owned that has a comb filter, and it makes all the difference in the world in the picture.

As to SRS sound, my flat screen also has it, with two 3" speakers mounted at the base of the cabinet under the display, which fires the sound directly downward -- in my case, to the top of the utility cart on which the TV sits. Haven't noticed any difference in sound quality in the year-plus I've had the TV, although I sometimes must set the volume to near maximum to get sound loud enough to hear (I sit about ten feet away from the set). This is a flaw in the design of the television, which can only be compensated for by the use of a sound bar or amplified speakers.

The reason your set sounds as you say it sounds, however, may well be due to the surround-sound system itself or it could be that, as you mentioned, the TV stations themselves are at fault for substandard quality of the stereo signal. Many local TV stations these days do not pay as much attention to sound quality as they should (giving much more attention to the picture), though I think they very well ought to see that the stereo sound as well is as good as they can get it; after all, many flat screens are used with 5.1 (or more) channel sound systems. The owners of these fancy (to say nothing of expensive) multi-channel audio systems have a right to expect excellent audio quality, but the sound output is only as good as the quality of the sound carrier of the transmitted signal. Your Sony XBR is an excellent TV set (it should be, for the amount of money these sets sell for), so you have every right on earth to expect top-notch picture and sound quality. However, as I said, if the audio carrier of the TV signal is of poor quality, the best audio system in the world won't make up for it. The other thing I just thought of is the input signal source to the TV. If you have cable, it could be that the cable system is processing the stereo audio carrier once, then it is processed once again by the stereo decoder system in your TV, and yet again by a 5.1-channel surround sound system, if you have one. Too much audio processing can and all too often does ruin what may have started out to be (when it left the TV station) a decent stereo sound signal.