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Looking for HDtv Converter Schematic

04/07/2008 8:01 AM

This should be a fairly simple box and I would like to build my own if I could find a schematic. I've ogled and googled but not found a thing.

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#1

Re: Looking for HDtv Converter Schematic

04/07/2008 10:56 PM

If I understand you correctly you seek to convert from NTSC, i.e., the present TV format to HDTV.

What makes you think that will comprise a "fairly simple box."

j.

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#2

Re: Looking for HDtv Converter Schematic

04/07/2008 11:39 PM

Go to texas instruments - www.ti.com and enter 'DaVinci hdtv' in the search box.

You're on your way!

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#3

Re: Looking for HDTV Converter Schematic

04/08/2008 9:30 AM

From what I know, HDTV has structural differences from the regular TV reception. We know that the definition of the picture on screen is given by the number of pixels in a scan line and the number of lines in a picture frame. While the present TV has a 525 lines / 60 frames per second(interlaced), HDTV 1024p is featuring 1920x1080 pixels at a higher frame repetition rate. A raw comparison would be: the present video signal has a bandwidth of 5.5MHz (that is the video has components from the very low Hz to maximum 5.5MHz -it is 4.5MHz for Europeans). A line scan is about 63 microseconds (because the interlacing, there are semi-frames). We have roughly less than 400 "pixels" in one scan line. Compare this with the 1920 for HDTV. The scanning on HDTV is 1080 lines per frame, compare that with the present 525 (from which we loose some during the vertical retracing).

We are talking fundamentals, not how a HDTV signal can be sent on the same signal with the regular one.

The DaVinci chip (I haven't seen the specs, therefore I cannot comment) would have to provide the conversion of a lower content of information from the 5.5MHz bandwidth to a higher one which I think is difficult. DaVinci has to have the tuner and IF circuitry matching the HDTV signal.

Also, the scanning system (including the CRT and the deflection coils) has to be adapted to the new scanning standards.

Audio? I don't think it needs any changes (actually, audio is the only one transmitted in frequency modulation in present TV signal)

So let's recapitulate:

If I want to make a TV set, that works at present standards, to work with high definition signal I need to:

-replace the tuner and IF circuitry

-add a DaVinci circuit (with all problems with circuits working close to GHz)

-replace deflection system.

-ah, I didn't mention the CRT (or LCD screen) that has to have a response time corresponding to the new speeds.

I am sure that there are more to say, but I am just drinking my first coffee, thinking to the day's chores...

But it can be done, good luck!

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#5
In reply to #3

Re: Looking for HDTV Converter Schematic

04/09/2008 8:46 AM

Actually I was just looking to build a signal converter that receives hdtv signal and degrades it to conventional signal for use on any old common tv set.

Thanks for the information though, I always wondered:>)

lj

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#6
In reply to #5

Re: Looking for HDTV Converter Schematic

04/09/2008 9:01 AM

Due to the way HDTV is protected, there has to be (at least for the moment) a special chip in your "box" that will decode certain signals for you.

There was a company at one time here in Germany producing such a unit, but the "big boys" killed it off REAL quick!!!! They even used the correct chips, but it did not help them!!!

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#4

Re: Looking for HDtv Converter Schematic

04/08/2008 6:57 PM

You say converter but from what to what? For HDTV you can have HDMI, Component, DVI, RGB. For Normal TV you can have Composite, S-Video. What's your source and what's your destination?

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#7
In reply to #4

Re: Looking for HDTV Converter Schematic

04/09/2008 12:45 PM

Source is TV station transmitted HDTV programming signal which will be received via airiel aluminum antenna. destination will be a standard non HDTV set. I am not looking to convert my TV to HDTV.

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#8
In reply to #7

Re: Looking for HDTV Converter Schematic

04/10/2008 8:34 AM

Buy a converter. You could not build one any cheaper......the test equipment that you will need for setting up etc., will cost more.....

Due to the secret coding, I seriously doubt that anyone will actually manage to decode this very quickly.

But they said this about the DVD and a Swedish(?) schoolboy managed it!! But I am guessing, but I somehow feel that lightning will not strike twice in the same place.....

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#9

Re: Looking for HDtv Converter Schematic

05/01/2008 10:52 AM

Even if you could do the hardware, I bet you will have a hard time with the software decoding of the MPEG digital data stream. You don't say where you are located. Here in the USA, with the end of analog over-the-air TV coming in February 2009, the HDTV (ATSC over-the-air) converters are around $50. If you request coupons from the government, the cost is $10 ($40 coupons/two max per household, just bought mine a few days ago). Don't think you can build one for less, and if this is just for a fun project, I can think of many other projects that would be more fun (my opinion)

See;

www.dtv.gov

Of course, this only applies if you are talking about US based over-the-air TV trasmission.

Hope that helps,

Tom

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#10

Re: Looking for HDtv Converter Schematic

02/26/2010 2:56 AM

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