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CRT gamma correction


I enjoyed the article about CRT gamma in the January 2005 issue of Broadcast Engineering.

I can't tell you how many times over the past 20 years I have tried to explain the problem of CRT gamma correction to people. I was told repeatedly not to worry about something that didn't matter.

Well, I guess when the FCC is asked by Congress and the president to have its commission headed by broadcast engineers (not lawyers) to come up with a standard for digital broadcast, they will resolve all of these analog problems. Some, but not all, of the problems that the FCC will resolve might include making one digital standard for everyone to manufacture and use, one TV tuner or one set-top box, one recording format, and one compression scheme.

For frame rate, (29.94, 30, 24) interlace/progressive, drop frame/non-drop frame, set-up level (7.5 IRE 0 RE) and 100 percent white (235 or 256) and a few other items that don't make life simple.

In sync

Mr. Luff,

In the analog domain, we have to do horizontal and subcarrier timing with the machines so they are in sync in a switcher. Is it the same in the digital domain? I think that there is timing to do, but the timing window is wider than in analog. There must be timing to do; otherwise, they would not put an out of sync light on our digital Saturn switcher (BTS). When the machines are not in sync, you cannot do a wipe, and you see the image with a vertical sync problem.
Jean-Francois mathieu musique plus

John Luff responds:

The simple answer is that timing is just the same with digital as analog signals. The references used are the SAV/EAV signals. Digital video switchers are generally very forgiving, usually +/- 1/2 line or more. The vertical timing is just as critical as with analog. Hope that helps.

PVS problem

Hello Brad:

I am currently in Guadalajara, Mexico, and have just acquired one of Utah Scientific's switchers of the PVS series, but I don't have any training, and the service/operations manual is incorrect, so you can imagine how confused I am!

Utah Scientific stopped selling these devices more than 10 years ago. Do you know where I can get a copy of the original manuals?

Utah Scientic responds:

I have recently learned of your request for technical support on the Utah Scientific PVS-series switcher.

As you know, this product was discontinued more than 10 years ago. However, it is the long-standing policy of Utah Scientific to provide all possible technical support for our products — regardless of age.

In keeping with this policy, we have an arrangement with a technical support company to provide customer assistance on the PVS-series switchers. Your request has been forwarded to this company, and we are confident they will contact you shortly to determine what is required to bring your system up to full operating condition.

If you have any questions or need any further help with any of our products, please do not hesitate to contact me.

December Freezeframe:

In December, we asked readers to name the winners of the 2003 Broadcast Engineering Excellence Awards.


Rich Brockman
Rich Lohmueller
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Karl Sargent
Peter J. Houghton

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