Wanting to build an hdtv tuner

[Shaun Perez]

I have searched and can't find a diy hdtv tuner. I do not think that the $500-$800 price is at all worth it and so I was just waiting for it to drop but i would much rather build my own! Any one know where I could get a schematic?

[Schaef]

There are a couple of problems with this. First, a HDTV tuner is not just simply figuring out how to pull the signal out of the air or off the cable. With DTV in general, the problem starts with that "D" meaning Digital. In addition to pulling the signal out of the air, you also need to decode it, and that involves DSPs and other sophiscated equipment. Are they worth the $500-800 they're charging, not really, but they're not as cheap as a regular old tuner.

In other words, a schematic is only half the battle, next you need the code to decipher that signal, and good luck getting that in the DIY market!

[HDTVman]

Shaun; you won't find any HDTV DIY tuners for quite some time yet. There are several reasons for this:

A much better tuner is required with very low phase noise.

A VSB (for over the air) or QAM (for cable) demodulator is required that has a very complex digital equalizer built in.

Next a multi mode mpeg decoder is needed to decode the data stream into video, audio, channel table onfo, and about 20 other different types of data.

Now all that you need to do is format the video into the correct video format for your display, there are only 36 different possible formats.

Keep in mind that no one is selling there custom IC chips on the open market yet so you would need to do all of this stuff in EPLDs. My guess is that your DIY tuner would cost about $3k in parts.

Or you could wait untill about Christmas time. You should start to see Over The Air only tuners for ~ $300-$400 by then. The $600-$800 dollar ones your talking about are SAT + OTA.

Later
Bruce

PS; as for the schematic. The ones for our sets are about 15 pages and no you can't have one.

[Shaun Perez]

oh, ok, thank you I understand now

[Brian Guralnick]

Originally posted by HDTVman
PS; as for the schematic. The ones for our sets are about 15 pages and no you can't have one.

15 pages, little over complicated. I am investigating the possibility of making a universal xQAM & xQFSK analog/digital receiver. Over 90% of the design is 1 PLD, 1 IF adc for the IF stage. The IF demodulation will be all digital. It will even have a programmable LMB power supply for dish units.

The huge problem here is not getting the data stream from the RF tuner, or mpeg decoder, or video out being HDTV Pxxxx, or even composite, it's mainly getting the method of data packing & encryption junk.

BTW, even huge PLDs are not as expensive as they used to be. Take a look at Altera's Cyclone for example.

[HDTVman]

Brian: Are you talking about HDTV (1920 X 1080) or SDTV (704 X 480). Big difference in data rate HD 19.39 mbps SD 2-3 mbps per data stream. QAM and QFSK have been aroud for a long time and you can get those parts. Not the same as over the air HDTV.

By the way 15 pages includes PS, display drivers, control micros audio section (5.1 and 2 channel output plus left, right and center amps.), RF tuner and every thing else broken down by section. Could it be put on one page? Ya, but who could read it, or hold it?

Later
Bruce

PS: The chip makers will sell there chips if you can show you are a manufacturer.

[Brian Guralnick]

All modes.

I use 2 RF stage tuners without the SAW filters. 1 from Sharp. #1 tunes from 850Mhz to 2.5Ghz. The IF out is 350Mhz. The second is a custom which mixes the 50-900 band into the Sharp tuner.

I'm getting a clean 100Mhz Bandwidth. I suprised a few guys here in Montreal when I managed to digitally demodulate 2 adjacent C band channels simultaneously using the 1 tuner.

As for sampling the IF signal, Im using 4x200MSPS 10 bit ADCs.

My IPs I've completed in verilog so far: These are in use right now in a current design.
----------------------------------------------------
DDR SDram multi channel/multi port DMA controler. (currently running 1.2Gbyte/sec.)
Programable Genlockable Raster & graphics generator. (Up to 200Mhz, so, all the HDTV Pxxx modes + higher scan rates for pro video projectors.)
Frame rate buffer resynchroniser/scan rate converter.
YUV/RGB, & RGB/YUV converters.
NTSC/SVIDEO -> component demodulator.
Video scaler, 16:9 to 4:3, & 4:3 to 16:9.
----------------------------------------------------

Things to finish:
FFT based demodulator + multiple secondary subcarier demodulators.
Data reciever modem. Will be software bit rate interpreted. I expect my maximum bitrate to be at the 250mbit/sec.

Things to start:
MPEG2 engine.
USB2.0 IO PC link. -> this should really anger the MPAA.

[alvaius]

Brian, this sounds more like a commercial product that you are developing or are you a DIYER with too much free time? :-)

[Brian Guralnick]

Comercial product.

[jgwinner]

Brian, I'll buy one!

I'm on cable, and I don't think Time Warner has an HDTV decoder (or at least they didn't last time I looked). I'm on cable as I get Broadband internet that way - I'd rather have my Internet than HDTV SAT. Guess I could get both

HDTVman, what decoder is this, or if you tell us do you have to kill us?