8VSB demodulator tricks - AVS Forum
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post #1 of 25 Old 02-20-2009, 03:39 AM - Thread Starter
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I've found a brand new evaluation board for the ATI/AMD T316 8VSB and QAM demodulator chip. It come with a Windows User Interface that interacts with the board over USB. Here's what it looks like on my PC:



The UI controls the tuner and show if there is MPEG-2 frame lock. Separate windows show the demodulator status and AGC status. I'm also running a DVB-ASI capture program (Enensys DiviCatch) and VLC to decode the MPEG-2 Transport Stream from the eval card.

I took some measurements on my strongest signal, KNTV-DT on RF channel 12. Here's the results:
Code:
Attenuation   Equalizer S/N         AGC%       # of Pre RS errors/sec
0  dB             32.0              40            0
10 dB             32.0              40            0
20 dB             32.0              43            0
30 dB             30.5              52            0
40 dB             24.3              61            0
43 dB             22.1              64            0
46 dB             19.7              67           <1
47 dB             18.5              68           <10
48 dB             17.6              70           <1000
49 dB             16.6              72           <10000
50 dB             15.7              74           <100000 heavily impaired
51 dB         loss of lock
KNTV-DT delivers a rock crushing signal to my lab in Milpitas, CA. It's at least 43 dB more than necessary for perfect reception. Also note that the difference between a watchable signal (at 49 dB of attenuation) and no signal (at 51 dB of attenuation) is only 2 dB.

Here's the KNTV-DT 8VSB constellation diagram with 10 dB of attenuation:



The eval board works better than my old Samsung SIR-T165 receiver. I had actually thought KCNS-DT was off the air, but in reality, it's just too weak for the Samsung. Here's the constellation for KCNS-DT on RF channel 39 when it was pretty impaired on the eval card (and non-existent on the Samsung):



Ron

HD MPEG-2 Test Patterns http://www.w6rz.net
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post #2 of 25 Old 02-20-2009, 06:54 AM
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Thanks dr1394. What is this? Is it a prototype for a PC ATSC tuner card? Not yet available commercially?
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post #3 of 25 Old 02-20-2009, 07:57 AM
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Where did you get it and for how much?

Rory
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post #4 of 25 Old 02-20-2009, 03:42 PM
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Quote:
Originally Posted by otaguy View Post

What is this? Is it a prototype for a PC ATSC tuner card? Not yet available commercially?

Hi there

dr1394 already wrote that it's an evaluation board.
Eval boards are manufactured and sold by chip manufacturers to promote their chips to board and product designers/manufacturers. The eval board is used instead of having to start from scratch (on-paper design and then build a prototype). Eval boards tend to be expensive (compared to the chip that it's promoting). An eval board may incorporate some features of a reference design, but a reference design should be closer to resembling a real "product".

Regards
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post #5 of 25 Old 02-20-2009, 10:05 PM
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I am aware that it is an evaluation board not a consumer product. I spent quite a number of years designing broadcast television equipment for GVG both as an employee and later as a contract engineer and would still like to get one if the price is not out of reason.

Rory
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post #6 of 25 Old 02-21-2009, 03:36 AM - Thread Starter
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Quote:
Originally Posted by Rory Boyce View Post

Where did you get it and for how much?

To be honest, I found it in a box at work. It was bought a couple of years ago when we were developing the ATSC capable DVD recorders for Panasonic (the EZ series). I'm not sure how much it costs, but as blue_z suggests, it's probably pretty expensive. Eval boards are typically priced very high to make sure you're a serious customer (and also because they are very low volume). Here's a photo of the set up:



The left board is the USB controller and Transport Stream I/O. The green cable is plugged into the DVB-ASI output. The center board is the T316 demodulator chip. The right board is the tuner and RF/IF strip. The tuner board is by far the most interesting as it contains several different AGC options (for different end product cost levels) and has a pretty good LNA chip, the Maxim MAX3538 (5 dB noise figure).

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4494

There's also a Smart Antenna interface (not enabled):



And also a channel power display:

KNTV-DT


KCNS-DT


You can see the multipath distortion on KCNS-DT and the audio carrier of KNTV analog on the low end of the KNTV-DT plot.

The ATI/AMD demodulator product line has been bought by Broadcom. I searched the Broadcom website for the T316, and came up empty. It would seem that these boards are no longer available at any price.

Ron

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post #7 of 25 Old 02-21-2009, 07:37 AM
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Texas Instruments has an eval board for their TVP9900 chip, $499.
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post #8 of 25 Old 02-21-2009, 08:11 AM
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Quote:
Originally Posted by dr1394 View Post

I've found a brand new evaluation board for the ATI/AMD T316 8VSB and QAM demodulator chip. It come with a Windows User Interface that interacts with the board over USB.

Does that suggest that someone could construct a TV spectrum analyzer with a low budget USB interface?
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post #9 of 25 Old 02-21-2009, 06:21 PM
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dr1394:

To bad its no longer available, it looks like your kludge would be useful to have around as a piece of test equipment. After seeing your first post I did some searching and come up empty for the T316. Your second post explains why. In the past I had to create my own test equipment more than once when designing various pieces of new television equipment.

Rory
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post #10 of 25 Old 02-21-2009, 06:56 PM - Thread Starter
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Quote:
Originally Posted by Tower Guy View Post

Does that suggest that someone could construct a TV spectrum analyzer with a low budget USB interface?

That's already been done. Just Google "usb spectrum analyzer". Lot's of products out there.

The power spectrum display on the T316 eval card is just showing the IF level at the demodulator after AGC. In the two pics I posted, the IF power is almost identical, but the the actual RF signals are about 40 dB different.

Ron

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post #11 of 25 Old 02-21-2009, 07:06 PM - Thread Starter
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Quote:
Originally Posted by Rory Boyce View Post

dr1394:

To bad its no longer available, it looks like your kludge would be useful to have around as a piece of test equipment. After seeing your first post I did some searching and come up empty for the T316. Your second post explains why. In the past I had to create my own test equipment more than once when designing various pieces of new television equipment.

I thought it would be interesting to show the hidden features that are available on these demodulator chips. Manufacturers could chose to include all of these measurements in their products, but of course they are much to "techie" for the average consumer. However, I'd have to say that the demodulator signal to noise ratio and the number of errors from the convolutional decoder are the most useful and should be included in all designs.

Ron

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post #12 of 25 Old 02-22-2009, 03:39 AM
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Quote:
Originally Posted by dr1394 View Post

I thought it would be interesting to show the hidden features that are available on these demodulator chips. Manufacturers could chose to include all of these measurements in their products, but of course they are much to "techie" for the average consumer. However, I'd have to say that the demodulator signal to noise ratio and the number of errors from the convolutional decoder are the most useful and should be included in all designs.

Ron

My first DVB-T receiver, the Pace DTVA (which was a neat single cable design, where the Power and Antenna/Aerial feeds went into the main SCART connector that output RGB/Composite/Stereo/WSS to the TV, meaning only a single cable between box and TV) had two error displays when tuning. One showed the total number of errors, the other the number of uncorrectable errors remaining.

(*) Annoyingly this first gen DTVA is likely to be rendered obsolete when the UK switches off analogue TV, as the changes to the UK DVB-T model mean that some early receivers won't be compatible. Quite a major issue over here... On the other hand it will be 12 years old by then...
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post #13 of 25 Old 02-22-2009, 05:42 AM
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Quote:
Originally Posted by dr1394 View Post

That's already been done. Just Google "usb spectrum analyzer".

Would you be so kind as to share your favorite model number? I'm looking for something in the high-end consumer price range.

There are plenty of true instuments with a USB interface in the 3K price range.

The Wi-Spy does 2.4 ghz only.

There are others from the UK with prices up near 1K US.

There's a sampling scope with a spectrum analyzer display, but it has a bandwidth of 100 mhz.
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post #14 of 25 Old 02-22-2009, 07:11 AM
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dr1394,
Regarding HD spectrum analyzers, do you recall what computer capabilities were necessary for your plot (sublinked) of a stadium crowd scene using the free/low-cost shareware FFT software from SigView? You mentioned it was an uncompressed 4:2:2 YCbCr source. Notice you've recently added some 4:2:2 sources to your software site .

Surprised others haven't posted image analysis with SigView's program. One AVSer posted that he thought it only worked with audio(?)

Wonder if plots such as your SigView tryout are precise enough to make significant differentiations between the higher resolution content of standard in-home HD images?
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post #15 of 25 Old 02-22-2009, 10:36 AM
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Dr., Is there any way I can rent this from you for a few days to evaluate some problems with my signals?

See this thread.

Thanks,

~ryan
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post #16 of 25 Old 02-22-2009, 04:52 PM - Thread Starter
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Quote:
Originally Posted by Tower Guy View Post

Would you be so kind as to share your favorite model number? I'm looking for something in the high-end consumer price range.

There are plenty of true instruments with a USB interface in the 3K price range.

The Wi-Spy does 2.4 ghz only.

There are others from the UK with prices up near 1K US.

There's a sampling scope with a spectrum analyzer display, but it has a bandwidth of 100 mhz.

I can't say I've ever used any of these USB based instruments. I have the luxury of HP and Agilent analyzers available to me at work. If $3000 is within your price range, you might be interested in this portable analyzer:

http://www.lptech.com/LPT-2250.html

I think it's around $2700.

Ron

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post #17 of 25 Old 02-23-2009, 10:59 AM
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Quote:
Originally Posted by dr1394 View Post

I can't say I've ever used any of these USB based instruments.

I thought so.

I had tried the exact google search that you mentioned before your suggestion and didn't find anything cheap for measuring antenna signal strengths.
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post #18 of 25 Old 08-22-2011, 04:04 AM - Thread Starter
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Sorry to resurrect this thread, but one of my ham radio friends has discovered a fairly low cost USB based spectrum analyzer. It's the Signal Hound at $919.

http://www.signalhound.com/

http://www.youtube.com/watch?v=6GBRKABob-k

Ron

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post #19 of 25 Old 08-22-2011, 07:02 AM
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Darn, why are these fun toys never Linux-compatible? I'd have a new item for my wishlist if it was.

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post #20 of 25 Old 08-24-2011, 08:02 PM
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Darn, why are these fun toys never Linux-compatible?

Because desktop Linux is a joke.
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post #21 of 25 Old 08-24-2011, 09:24 PM
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Because desktop Linux is a joke.

It's not as funny a joke as Windows though.
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post #22 of 25 Old 08-24-2011, 09:27 PM
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It's not as funny a joke as Windows though.

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post #23 of 25 Old 08-25-2011, 08:18 AM
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Darn, why are these fun toys never Linux-compatible? I'd have a new item for my wishlist if it was.

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post #24 of 25 Old 08-25-2011, 08:31 AM
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Quote:
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WINE ... don't whine?

I have yet to make WINE work with any USB device. And not for lack of trying.

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post #25 of 25 Old 08-27-2011, 04:51 AM - Thread Starter
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It's difficult for me to get religious about any operating system, since I've used so many.

CP/M-80
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PC-DOS 1.1 through 5.0
Windows 3.1
Windows 95
Windows 98
Windows ME
Windows XP

SunOS
Solaris with OpenWindows
Solaris with CDE

Ubuntu
Fedora
CentOS

iRMX
VRTX
VxWorks

At my last job, I had four boxes running Solaris, Windows XP, Ubuntu and Fedora respectively. Each one had something special that it could do and couldn't be done otherwise. Window XP is just so ubiquitous, that I can't see doing without it. The only thing that really rubs me the wrong way on Windows is Outlook.

If I had to pick a favorite, it would be Solaris. There's just something professional feeling about a box that (almost) never has to be rebooted. Of course, it's the least useful in terms of third party anything.

The same goes for text editors. I've used so many that they're just a big jumble in my head (especially ones like vi). My current editor of choice is notepad++.

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