Any recent 5th generation receiver chip news? - Page 12 - AVS Forum
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post #331 of 433 Old 08-17-2005, 01:16 PM
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Quote:
Originally Posted by holl_ands View Post

Almost forgot: Nokia DVB-T COFDM blew them all out of the water on this test. It could sustain D/E between 0 and 1 dB at up to +/-74 us pre/post echo delays.

At what bandwidth (6, 7 or 8 MHz), and data rate?
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post #332 of 433 Old 08-17-2005, 05:44 PM
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Quote:
Originally Posted by holl_ands View Post

SO WHAT'S IN YOUR STB???

Pop the cover off and let us know what Tuner Model number you find.
Opening the Tuner itself is highly discouraged, but you might see the part number
of the big ATSC Decoder chip on the main board or poking through the Tuner's view window....

Can't see inside the tuner housing, but ZenithHDV420 has 2 LG labled IC's on the main board :

LGDT1301A - did a bit of googling, and can't find much info on it, except who has it "in stock"....

LGDT3102 - I think this is the one we're interested in. Quite a bit of info from LG on it(currently anyway) at below link here :

http://64.233.161.104/search?q=cache...LGDT3102&hl=en

Note: You don't need "Korean Language support", It's in English ...

Above link is from a google cache, unfortunetly I'm currently getting a dead link at the google referenced link at : http://sic.lge.com/products/AdvancedVSBReceiver.htm

--------------------------

I may be wrong and it might be 3rd generation, but I *think* the HDV420 was LG/Zenith's first use of their 4th generation chip ... At least that is what a LG rep who used to post here under handle of "Jferg" and on a few other forms had told us ...

I'd check my Hisense DB-2010 as well, except that it is a recent purchase and has a "Warranty Void if removed" sticker which will be "broken" if I take the cover off ... I Think we already know what is in there (ATI), but when warranty runs out I'll probably take a look anyway, especially since the thing seems to run so hot ...

Attached pic#1 is of the LG labled chips on the HDV420's Main board(Main board is labeled "LST-2101Z"), BTW.

Just for fun, also attached below is "full view" of HDV420's innards ... Not much to it, as you can see ... tuner can, main board, power supply and connections on the back/a few buttons on the front is about it ...

BTW ... I had taken the cover off HDV420 almost 3 years ago when I first got it. As, like many VCR's it uses a "mini" in-line amp(or "powered splitter") as it splits the signal from it's RF in jack to go to both : #1.) Tuner, #2) It's RF Out jack ... I wanted to, for instance see what happened with weak "DX" signals on 1st adjacent channels to strong local signals(NTSC+ATSC) with and without that little "amp" in line ... Given the "RF enviornment"+ my antenna setup "circumstance" It doesn't seem to be really "helping any" --- but, doesn't really seem to be hurting anything either .... So, as you can see in the 2nd Pic I ended up hooking it back up, since I have a use for its RF out jack ....... I suspect however that the little in line-amp it has may be a good part of the reason why a 10db attenuator and "strong signal warning" in the manual was included ... Anyway ... on that first occasion of opening the box, (silly me!) I did not take a photo -- The "hard part" both times didn't involve a screwdriver, but getting the thing unhooked and "out of the rack", which required a bit of time as well as a bit of a contortion act on my part ....
LL
LL

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post #333 of 433 Old 08-17-2005, 06:37 PM
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Quote:
Originally Posted by holl_ands
Almost forgot: Nokia DVB-T COFDM blew them all out of the water on this test. It could sustain D/E between 0 and 1 dB at up to +/-74 us pre/post echo delays.


At what bandwidth (6, 7 or 8 MHz), and data rate?

The Field Test Report says 19.76 Mbps, hence roughly same as ATSC data rate.
But it didn't say at which bandwidth.
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post #334 of 433 Old 08-17-2005, 07:02 PM
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Nitewatchman: What numbers are on the tuner can? Can't quite make them out.

========================================================
The spec you cited claims a "Ghost cancellation range" of -11 to +44.5 us,
and (as usual) does not stipulate under what test conditions....

Looking at Figure 1 in the IEEE article re the Zenith/LG 5th Gen Receiver,
the LGDT3102 numbers seem to be closest to the 4th Gen equalizer range,
whereas the 3rd Gen performance was about -8 us to +44 us.

Just to add to the confusion, it is not always clear whether the LGDT3302A
(reportedly used in the LST-4200A) is 4th or 5th Gen, esp. since it is pin-for-pin
the same as the latest 5th Gen LGDT3303. [Maybe it's Gen 4.5....]
It is very hard to correlate the Zenith Prototype results to production chips
when they don't publish the important performance specs.

======================================================
ATI press releases clearly state that the NXT2004 is used in the Hisense
USDTV/Walmart STB's (i.e. the DB-2010 without the DVI/HDMI interface).
Surely there is someone else out there whose warranty has expired who can
take a look at the tuner module part number...
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post #335 of 433 Old 08-17-2005, 08:18 PM
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Quote:
Originally Posted by holl_ands View Post

Nitewatchman: What numbers are on the tuner can? Can't quite make them out.

"Close up" image of top of tuner attached farther below.

I think it's :

DPC-A902P Or DPC-H902P
20821-1100

Quote:
Originally Posted by holl_ands View Post

The spec you cited claims a "Ghost cancellation range" of -11 to +44.5 us,
and (as usual) does not stipulate under what test conditions....

Yes ... It is the only thing I could find, however ....


------------------------------------------------------------

If this hasn't been posted yet ... On another note ATSC docment A54 "Guide to the use of ATSC DTV Standard"(latest revision A54a - Nov 2003), specifically sections 8(RF Transmission)+9(Receiver Systems) contains quite a bit of good info for those interested in ATSC(8VSB) transmission, reception and receiver design issues. It is currently available here:

http://www.atsc.org/standards/a_54a.pdf
LL

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post #336 of 433 Old 08-18-2005, 10:46 AM
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Quote:
Originally Posted by holl_ands View Post

At what bandwidth (6, 7 or 8 MHz), and data rate?

The Field Test Report says 19.76 Mbps, hence roughly same as ATSC data rate.
But it didn't say at which bandwidth.

If the BW was 6 MHz then it would bode well for the Nokia DVB-T, if the BW was 8 MHz then we have an apple and orange comparison for this test.
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post #337 of 433 Old 08-18-2005, 02:18 PM
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Micronas finally announced an ATSC Decoder IC:
http://www.micronas.com/press/pressr...ar=2005&lang=1

Micronas talks about 0 dB Echos, but they never quite say whether they succeeded in
actually working under these difficult conditions.
(The Zenith/LG 5th Gen Prototype failed several of the "0 dB Echo" tests).
I would have been more impressed if they had at least claimed to have met the
ATSC A/74 Receiver Guidelines.
No spec sheets available yet on Micronas website....not that they'll tell you much anyway....

Zarlink, who makes the SL2610 Mixer/Osc IC for Thomson's DPF88XX Tuner Module,
claims FULL SPEC COMPLIANCE for ATSC A/74 (whatever that means, given that the very
long equalizer numbers are for large D/E ratios that fall into the "suggested extension"
category: http://products.zarlink.com/product_...homson_pnp.htm

If you read the fine print at the end of the article, you'll see that the excellent adjacent
channel results are partially due to the ATI Theater 313 ATSC Decoder IC and partially
due to an unnamed RF Front End chip design that provides an excellent -86 dBm sensitivity
(that's 4.5 dB Noise Figure). So, which STBs and/or TVs employ the DPF88XX....

And the ATI Theater 310 series since that's where most of the A/74 spec compliance comes from...
http://www.eetimes.com/showArticle.j...cleID=55300593
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post #338 of 433 Old 08-19-2005, 06:01 AM
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To restate holl_and's post somewhat....

Micronas has finally launched the ATSC decoder chip based on the well-known Linx prototype shown years ago. Because of the seemingly endless delays, many had wondered if the chip would ever come to market. This is really good news for free OTA HDTV enthusiasts.

From the article:

"primeD is based on design work undertaken by a team of US DTV experts, who came to Micronas as part of its May, 2004 acquisition of LINX Electronics, a leader in 8VSB demodulator design" according to Hans-Juergen Désor, Vice President Consumer Products at Micronas. "The LINX acquisition combines LINX DTV expertise with Micronas DVB technology to create a single-chip solution for digital TV".

"Unlike most competitors' implementations, Micronas' DRX-H demodulator does not simply discard undesired echoes but combines them in a unique patented manner with the desired signal which results in superior performance under realistic field conditions. We are approaching theoretical limits of the 8VSB demodulation standard thanks to our unique implementation" said Rich Citta, Chief Scientist of Micronas Semiconductors, Inc., an industry veteran and one of the key architects of the current ATSC DTV standard.

Offering the highest level of integration and performance of any solution on the market today, the DRX-H integrates an ATSC A/53-compliant 8VSB demodulator with an ITU-T J.83 Annex B-compliant QAM demodulator, a high quality NTSC demodulator, and a BTSC decoder, as well as an OOB (Out of Band) QPSK demodulator and OOB Local Oscillator for seamless integration into DCR (Digital Cable Ready) television sets.
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post #339 of 433 Old 08-19-2005, 09:35 AM
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Rich and holl_ands,

I tried running your lat posts through a translator to convert it to Basic English for me to understand what you posted but it didn't change anything. What does all that mean? Better or equal to LG's 5th gen chip? Coming soon to a store near you?
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post #340 of 433 Old 08-19-2005, 01:53 PM
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OK, I'll try a Basic English summary, but I haven't written BASIC statements for awhile:

Numerous on-the-air tests have identified a fairly large number of specific locations that
had "sufficient' signal strength, but could not be decoded by 2nd or 3rd Generation STB's.
Both the 5th Gen Zenith/LG and the LINX Prototypes have been retested using a set of
"captured" RF test signals from these earlier tests (some are included in ATSC A/74).
There have also been some on-air tests that were repeated at the same locations that
caused problems in earlier tests. Both the Zenith/LG and LINX Prototype demonstrated
improvements by dramatically reducing the number of "problematic" locations. They also
are first STBs claiming to decode all of the captured Brazil test ensembles A-E.

The lab and on-air tests by Brazil and Australia compared the performance of several
different receiver systems, including ATSC, DBV-T and ISDB-T . See my 19July05 post:
http://hdtv.forsandiego.com/messages...html#POST19348

So some of the new ATSC Decoder IC's provide an important and dramatic improvement.
The difficult part is determining which is "better" when looking at the latest chips from
Zenith/LG, Micronas/LINX, ATI/NxtWave, Broadcom, Zoran/Oren, ST Microelectronics, et. al.
Adding to the confusion is lack of information on what was actually in the prototypes
and trying to associate Zenith/LG's generational jargon with IC and STB part numbers.

===========================================================
There has been a lot of hype about Zenith/LG's so-called 5th Gen ATSC Decoder IC.
Mark Shubin and Bill Miller have done a lot of tests in New York and and thus far
ONLY the Zenith/LG PROTOTYPE with the 5th Gen LGDT3303 IC truly succeeded in
Schubin's particular location where the multipath is extremely severe. An LG LCD
HDTV with the LGDT3303 chip was a close second. STB's with ATI NXT2004 didn't succeed.

Unfortunately, the DVICO FusionHDTV5 Gold PCI card, a new Prototype PCI card
from BTTI and another MIT STB Prototype with the LGDT3303 IC's did not operate
as well as the Zenith/LG Prototype. Right now there is some speculation as to WHY.
Could be the RF Front End in the Prototype was somehow "better". It is likely that
the prototype had different firmware than the production LGDT3303's. They also might
have had different firmware when tested by Schubin than that tested by the CRC lab.

The 5th Gen LG (as well as LINX, ATI Theater and Broadcom BCM3517/3520 ICs)
all claim big improvements in being able to handle a large pre-echo delay.
These large pre- and post-echo performance improvements may or may not be
important in Schubin's location. [Manufacturers need to display the equalizer settings!!!]

On-air test data has shown that for many locations the multipath consists of a single
strong signal plus several other delayed signals (multipath) that are at lower signal
strengths (typically 5-15+ dB lower). Even the 2nd and 3rd Generation STBs should
receive most of these signals, since the pre- and post-echo delays are "typically" well
within the A/74 Guidelines of -10 to +40us. The issue of extremely long equalizer delay
times is concerned with handling those rare cases when the (highly reflective) object
causing the reflection (presumably a skyscraper) is quite far away (50 us is a delta of
over 9 miles). For big city locations, this can be important. For most of us in the 'burbs,
it's probably not a concern.

The CRC lab test results above show that the Zenith/LG prototype had difficulties with
the so-called "0 dB Echo" test condition. For some other locations, especially urban and/or
indoor locations, there may not be a single strong signal because the direct path might be
blocked. For the worst case "0 dB Echo" case, all of the multipath signals have roughly the
same signal strength. The Micronas/LINX handled the "0 dB Echo" tests much better.
ATI/NxtWave has claimed that their NXT200x series, as well as Theater 310/313 series
of ICs can also handle this condition, but I have not seen any confirmation tests.

========================================================
Which brings us back to REALITY....sort of...
Mark Schubin and Bob Miller continue to invite manufacturers to subject their equipment to
a "real world" urban canyon environment where indoor antennas are the norm.
A Samsung test is currently underway....should learn more next few weeks....

The new MIT STB with 5th Gen LGDT3303 has not yet hit the streets.
I would like to see a test of other products, such as Broadcom and ATI Theater.
Micronas/LINX just announced long anticipated ATSC Decoder IC, maybe STB by early 2006?
I encourage people to see WHAT'S IN YOUR STB so we know what tuner/chip is in which product.

I continue to search for meaningful laboratory and on-air test reports for the current
generation of ATSC equipment so we can try to separate the hype and try to separate
the wheat from the chaff. Unfortunately, most lab tests are either on prototypes that
may or may not represent performance for a production unit, or are conducted by an
independent agency which cannot name names. Such as would probably be the case
if Brazil decides to conduct a update of their earlier ATSC vs DVB-T vs ISDB-T tests.

=======================================================
OK, let me close with a BASIC IF-THEN statement:

IF meaningful production test results, THEN can compare.
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post #341 of 433 Old 08-19-2005, 02:39 PM
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Quote:
Originally Posted by Micronas article View Post


From the Micronas article:

"Unlike most competitors' implementations, Micronas' DRX-H demodulator does not simply discard undesired echoes but combines them in a unique patented manner with the desired signal which results in superior performance under realistic field conditions. We are approaching theoretical limits of the 8VSB demodulation standard thanks to our unique implementation" said Rich Citta, Chief Scientist of Micronas Semiconductors, Inc., an industry veteran and one of the key architects of the current ATSC DTV standard.

Gee, if it were as simple as "discarding" undesired echos....
Anyone who knows about Adaptive Equalizers, will know that they work by
estimating the Channel Impulse function for the known PN-511 data sequence
and then setting the equalizer taps to minimze the mean square error.
This results in the phase of the individual multipath components being adjusted
so that they coherently add together. After that it can get complicated.....

Micronas may have a unique equalizer algoritm (doesn't everyone?), but it is
absurd to claim that their competitors algorithm (which is no doubt proprietary,
and hence unknowable to Micronas) operates in some sort of deficient approach
invented by Micronas's marketing staff.
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post #342 of 433 Old 08-19-2005, 03:04 PM
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Quote:
Originally Posted by holl_ands View Post

Micronas may have a unique equalizer algoritm (doesn't everyone?), but it is absurd to claim that their competitors algorithm (which is no doubt proprietary, and hence unknowable to Micronas) operates in some sort of deficient approach invented by Micronas's marketing staff.

You are entertaining dude!!

Keep the info coming. I know research like this is time consuming and I do appreciate your efforts. Same for Rich Peterson, I still have his first publication of the DBS Guide!!
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post #343 of 433 Old 08-21-2005, 10:46 AM
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holl_ands,

Thanks alot, much appreciated. I understand now.
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post #344 of 433 Old 08-24-2005, 04:17 PM
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I for one am hoping some other manufacturer comes out with a next gen tuner that blows away all the LG Gen-X vaporware.
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post #345 of 433 Old 10-11-2005, 03:05 PM
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Quote:
Originally Posted by holl_ands View Post

TEST REPORTS FOR ZENITH/LG 5TH GEN PROTOTYPE AND LINX/MICRONAS PROTOTYPE:

Finally found the Test Reports for the Zenith/LG 5th Gen Prototype STB, the LINX (now Micronas) Prototype STB
plus a Field Test Report for the LINX Prototype STB compared to an older Harris ATSC STB (plus some Nokia COFDM STB equalizer tests):

1. Performance of 5th Generation 8-VSB Receivers, Laud, Aitken, Brett and Kwak,
IEEE Trans on Consumer Electronics, Vol 50, No 4, Nov 2004.

2. An ATSC DTV Receiver with Improved Robustness to Multipath and Distributed Transmission Environments,
Wu, Wang, Citta, et. al., IEEE Trans on Broadcasting, Vol 50, No 1, Mar 2004.

3. Results of the Lab Evaluation of Zenith 5th Generation VSB TV Receiver, Communications Research Center (CRC, Canada), Sep 2003.

4. Field Tests of the LINX ATSC Prototype Receiver, Communications Research Center (CRC, Canada), Mar 2003.

5. Recent Performance Improvements to the ATSC Transmission System, Su, Wang, Salehian, et. al.,
Intl Broadcasting Convention (IBC) Conference Pub 2003. See http://www.crc.ca/en/html/crc/home/r...broadcast/rtnt

6. Results of the Lab Evaluation of LINX ATSC Prototype Receiver, Communications Research Center (CRC, Canada), Apr 2002.

IEEE refs are available on-line (for a fee) or from a well-equipped (University) library.
The first IEEE reference had the all important link to CRC reports: http://www.broadcastpapers.com/tvtra...RCATSCTran.pdf

======================================================
ATSC Doc A/74, Recommended Practice: Receiver Performance Guidelines, Jun 2004
says that a typical channel impulse response ranges from -10 us (pre-echo) to +40 us (post-echo).

A/74 then goes on to provide an Echo Delay performance profile for Single Static Echoes with various Desired to Echo Ratios:

from 0 to +5 us (for D/E > 1 dB) [Note: 0 dB Echo is not stipulated.]
from -5 to +10 us (for D/E > 2 dB)
from -5 to +20 us (for D/E > 3 dB)
from -10 to +40 us (for D/E > 5 dB) [The typical response cited above.]
from -20 to +40 us (for D/E > 7.5 dB) [Suggested Extension]
from -25 to +50 us (for D/E > 16 dB) [Suggested Extension]

So A/74 expects the typical impulse response to have a D/E > 5 dB and the so-called 0 dB Echo
or equal strength signals are expected to have a fairly small delay.
And extremely long pre-echo or post-echo signals would be at a much lower level than the desired signal.
[Indeed, if the echoes are much more than a D/E of 16 dB, they could be expected to cause minimal if any degradation.]

=======================================================
Based on these tests, if you don't need extremely long pre and post-echo performance,
the LINX/Micronas prototype clearly had better overall performance.
And when Zenith/LG claims +/- 50 us equalizer capability,
they must mean when the Echo is 10 dB or more below the Desired signal.
Note they avoided mentioning performance for A/74 stipulated typical condition (D/E = 5 dB),
because both units failed to meet that guideline.

So it is impossible to compare manufacturer equalizer "claims" unless they also stipulate the test conditions!!!!

Of course, performance for production units may be different.

CRC recently added the fol. report on a Prototype Samsung ATSC Receiver:
http://www.crc.ca/en/html/crc/home/r...broadcast/rtnt
"Lab. Eval. of a Prototype Samsung ATSC Receiver" dtg 30Aug05.
The Samsung prototype uses a commercially available ALPS Tuner Module and
Samsung's "Gemini" ATSC Decoder chip (whatever that is...)

The ALPS Tuner Module has a desired signal overload point of +1.5 dBm and
a sensitivity of -84.7 dBm (that's a Noise Figure of about 6 dB).
Perhaps it's the Alps Electric TEQH Tuner Module???

Samsung performance met all ATSC A/74 Guidelines (unlike other tested prototypes),
with performance under most test conditions, exceeding the performance of both
the Zenith/LG Prototype and the two versions of Linx (now Micronas) Prototypes.

Under marginal SNR conditions, the Samsung could not handle low delay echos
(< 1 usec, i.e. less than 0.2 mile path differential),
where the multipath components are within a few dB of each other.
This can occur when there are nearby reflecting objects
(e.g. your neighbor's house and/or your interior/attic location).

Nonetheless the Samsumg Prototype still outperformed the Linx and
especially the Zenith/LG Prototypes under these so-called "zero echo" test conditions.

As always, these are results for PROTOTYPE equipments and may or may not
be representative of (hopefully improved) production equipment.

I also have been unable to determine exactly WHAT was in the Linx (Micronas)
and Zenith/LG Prototypes relative to production chips....
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post #346 of 433 Old 10-12-2005, 11:14 AM
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Thanks for another of your exhaustive reports, holl_ands. Probably not digesting the final 'graphs enough, but the test conclusions seem contradictory: it outperformed the Zenith/LG yet couldn't handle short-delay signals, which presumably made the LG design so good at Mark Schubin's heavy-multipath NYC location.

(Also, at a NYC location here, only ~9 blocks from NYC's transmitter, but with no view of it, only reflections, and can't tune any HD signals reliably with a Silver Sensor and an early-generation tuner built into my year-2000 Philips RPTV. Yup, not a good combination. But the still-unavailable Zenith/LG combo sounded promising--even here.) Rely on two cable subscriptions. -- John
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post #347 of 433 Old 10-12-2005, 01:14 PM
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See my earlier summaries comparing Linx (Micronas) Prototype to Zenith/LG Prototype:
http://www.avsforum.com/avs-vb/showt...rc#post6041081
http://www.avsforum.com/avs-vb/showt...rc#post6059066

The PROTOTYPE Zenith/LG tested by CRD performed considerably worse than either the
Linx (Micronas) Prototype or the much more recent Samsung/Alps Prototype.
When tested, the Zenith/LG PROTOTYPE had great difficulty with short delay echo test conditions.

It has not been revealed whether there were any improvements made to the Zenith/LG PROTOTYPE prior to being tested at Mark Schubin's NYC apt.
Nor what improvments may or may not have been incorporated into the final LGDT3302 and LGDT3303 ATSC Decoder chips.

All we see are preliminary snapshots of performance....and thus far NOTHING re production units....

Nor anything, thus far, re the Broadcom, Orem, STMicroelectronics and the ATI chips (reportedly used in most HDTV's).
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post #348 of 433 Old 10-13-2005, 06:20 AM
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Quote:
Originally Posted by holl_ands View Post

See my earlier summaries comparing Linx (Micronas) Prototype to Zenith/LG Prototype:
http://www.avsforum.com/avs-vb/showt...rc#post6041081
http://www.avsforum.com/avs-vb/showt...rc#post6059066

The PROTOTYPE Zenith/LG tested by CRD performed considerably worse than either the
Linx (Micronas) Prototype or the much more recent Samsung/Alps Prototype.
When tested, the Zenith/LG PROTOTYPE had great difficulty with short delay echo test conditions.

It has not been revealed whether there were any improvements made to the Zenith/LG PROTOTYPE prior to being tested at Mark Schubin's NYC apt.
Nor what improvments may or may not have been incorporated into the final LGDT3302 and LGDT3303 ATSC Decoder chips.

All we see are preliminary snapshots of performance....and thus far NOTHING re production units....

Nor anything, thus far, re the Broadcom, Orem, STMicroelectronics and the ATI chips (reportedly used in most HDTV's).

I find it a little strange that the CRC test is so positive of this prototype, yet not even a press release from Samsung about its existence.
Maybe we'll get a little more info around CES time.
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post #349 of 433 Old 10-19-2005, 02:54 PM
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The fol. on-air measurements of sensitivity for various ATSC Receivers was
found in Echostar's 7/5/05 Reply Comments to the FCC re SHVERA rule making.
To find it, follow the link in Doug Lung's latest column:
http://www.tvtechnology.com/features...10.05.05.shtml

Measured Sensitivity by Channel (dBm)

D12 D23 D29 D41 D43 D47 D49 [DTV Channel Number]
-81.9 -82.6 -84.1 -82.8 -80.4 -81.1 -81.8 LG LST-4200A
-80.9 -80.6 -83.1 -80.8 -81.4 -81.1 -82.8 Samsung SIR-T451
-78.9 -83.6 -83.1 -83.8 -83.4 -82.1 -82.8 Motorola HDT-101
-81.7 -82.9 -84.1 -82.9 -82.8 -81.5 -81.9 Dish DP-942
-75.9 -78.6 -82.1 -77.8 -77.4 -78.1 -78.8 RCA DTC-100
-75.9 -78.6 -79.1 -77.8 -79.4 -79.1 -79.8 Zenith DTV Demod-S

Variation in Sensitivity:
5.8 5.0 5.0 6.0 6.0 4.0 4.0 dB

Average Sensitivity:
-79.9 -81.7 -83.3 -81.6 -81.1 -80.8 -81.6 dBm

FCC Performance Factor:
-81.2 -84.2 -84.2 -84.2 -84.2 -84.2 -84.2 dBm

========================================
To convert from Sensitivity to Noise Figure:
N.F. = Sensitivity (dBm) - (-106 dBm) (thermal noise floor) - 15.5 (dB) (minimum SNR for ATSC)

The thermal noise floor will vary somewhat with temperature (as measured at the first RF chip).

The minimum SNR for ATSC will vary somewhat between units and typically is slightly worse for both weak signals and very strong signals.
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post #350 of 433 Old 10-19-2005, 04:39 PM
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It should be noted that LG will incorporate the 5th gen tuner in the HD STB's they'll make for DirecTV.

'Better Living Through Modern, Expensive, Electronic Devices'

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post #351 of 433 Old 10-19-2005, 07:13 PM
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You can try out a 5th Gen. RX in the Divco Fusion 5 PCI card. I am using one and it absolutely works very fine using a plain old loop antenna inside an office complex with at least three walls between my PC and Open air. Also the office is at ground level. You to can try one out for $99 and a reasonably good PC.
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post #352 of 433 Old 10-20-2005, 06:33 PM
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[quote=holl_ands]The fol. on-air measurements of sensitivity for various ATSC Receivers was


Measured Sensitivity by Channel (dBm)

D12 D23 D29 D41 D43 D47 D49 [DTV Channel Number]
-81.9 -82.6 -84.1 -82.8 -80.4 -81.1 -81.8 LG LST-4200A
-80.9 -80.6 -83.1 -80.8 -81.4 -81.1 -82.8 Samsung SIR-T451
-78.9 -83.6 -83.1 -83.8 -83.4 -82.1 -82.8 Motorola HDT-101
-81.7 -82.9 -84.1 -82.9 -82.8 -81.5 -81.9 Dish DP-942
-75.9 -78.6 -82.1 -77.8 -77.4 -78.1 -78.8 RCA DTC-100
-75.9 -78.6 -79.1 -77.8 -79.4 -79.1 -79.8 Zenith DTV Demod-S


FCC Performance Factor:
-81.2 -84.2 -84.2 -84.2 -84.2 -84.2 -84.2 dBm

========================================
To convert from Sensitivity to Noise Figure:
N.F. = Sensitivity (dBm) - (-106 dBm) (thermal noise floor) - 15.5 (dB) (minimum SNR for ATSC)

The numbers given above are an excellent way to compare the various receivers' performance when given clean weak signals without the use of a preamp. They may not be valid when a preamp is used . If all the receivers meet the 15.5 SNR specification a good preamp would make all the receivers equal. The receivers' failure to meet the required sensitivity could be caused by a high noise figure or the receivers needing more than the specified 15.5 dB SNR.
The formula for noise figure is more complex and not linear in dB than the one given. For the -84.2 dBm sensitivity and 15.5 sensitivity I get 7.4 where yours is 6.3. The formula given permits negative values of noise figure, which does not happen. John
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post #353 of 433 Old 10-20-2005, 07:50 PM
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[quote=ctdish]
Quote:
Originally Posted by holl_ands View Post

The fol. on-air measurements of sensitivity for various ATSC Receivers was


Measured Sensitivity by Channel (dBm)

D12 D23 D29 D41 D43 D47 D49 [DTV Channel Number]
-81.9 -82.6 -84.1 -82.8 -80.4 -81.1 -81.8 LG LST-4200A
-80.9 -80.6 -83.1 -80.8 -81.4 -81.1 -82.8 Samsung SIR-T451
-78.9 -83.6 -83.1 -83.8 -83.4 -82.1 -82.8 Motorola HDT-101
-81.7 -82.9 -84.1 -82.9 -82.8 -81.5 -81.9 Dish DP-942
-75.9 -78.6 -82.1 -77.8 -77.4 -78.1 -78.8 RCA DTC-100
-75.9 -78.6 -79.1 -77.8 -79.4 -79.1 -79.8 Zenith DTV Demod-S


FCC Performance Factor:
-81.2 -84.2 -84.2 -84.2 -84.2 -84.2 -84.2 dBm

========================================
To convert from Sensitivity to Noise Figure:
N.F. = Sensitivity (dBm) - (-106 dBm) (thermal noise floor) - 15.5 (dB) (minimum SNR for ATSC)

The numbers given above are an excellent way to compare the various receivers' performance when given clean weak signals without the use of a preamp. They may not be valid when a preamp is used . If all the receivers meet the 15.5 SNR specification a good preamp would make all the receivers equal. The receivers' failure to meet the required sensitivity could be caused by a high noise figure or the receivers needing more than the specified 15.5 dB SNR.
The formula for noise figure is more complex and not linear in dB than the one given. For the -84.2 dBm sensitivity and 15.5 sensitivity I get 7.4 where yours is 6.3. The formula given permits negative values of noise figure, which does not happen. John

Their location is probably too close to use a Preamp.
You can't get negative noise figure numbers, because you'll NEVER measure a receiver sensitivity that it BETTER than the thermal noise floor.
By definition, the noise figure is the amount the noise level is raised over and above the thermal noise floor.
Since these were on-the-air tests (the best kind of user friendlly data in my opinion), there is likely to be a small amount of multipath degradation.
However most of the paths were LOS with minimal multipath expected.
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post #354 of 433 Old 10-21-2005, 09:43 AM
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Using receiver sensitivity and required SNR receiver noise power can be calculated by N.P. (dBv)= Sensitivity (dBm) - 15.5 (dB) (minimum SNR for ATSC)-30
np (watts) =10 ^ (N.P./10)
This can be converted to noise temperature by NT (deg k)=np/(KB)
where K is Boltzman's constant equal to 1.38*E-23 (J/K) and B is the Bandwidth assumed to be 6000000
This can be the converted to noise figure using the formula given here Using receiver sensitivity and required SNR receiver noise power can be calculated by N.P. (dBv)= Sensitivity (dBm) - 15.5 (dB) (minimum SNR for ATSC)-30
np (watts) =10 ^ (N.P./10)
This can be converted to noise temperature by NT (deg k)=np/(KB)
where K is Boltzman's constant equal to 1.38*E-23 (J/K) and B is the Bandwidth assumed to be 6000000
This can be the converted to noise figure using the formula given here
http://www.satsig.net/noise.htm
Here are two plots of sensitivity vs noise figure assunimg the required SNR of 15.5 and a 6 Mhz bandwidth.
Receivers can have a noise temperature well below the ambient temp of 290 deg. K and have sensitivities that are in theory not limited to any particular value. A 0.4 db noise figure UHF TV preamp is available comercially and narrowband single digit noise temperature can be built. The system noise temperature will determine the weakest signal that can actually be received. This will be the sum of the various contributions from the receiver, antenna and transmision line noise. I would think a TV antenna would have to have at least a 150 deg. K noise temperature. John
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post #355 of 433 Old 10-23-2005, 01:48 AM
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In Satellite systems, the external "Sky Temp" (and "Ground Temp") become very important, resulting in the calculation methodology you described above.
However, these are frequently EQUIVALENT Noise Temperatures selected to approximate what a thermal resistor would contribute to the overall noise level.
When the underlying noise statistics are no longer Gaussian (such as man-made interference), then the methodology becomes suspect.

The physical temperature of the antenna itself isn't important. The primary noise source is the first RF chip.
The physical temperature of the first RF chip in the Preamp (or Tuner) is what is important, plus adjustments for cascaded Noise Figure loss.

The first RF chip will be hotter than the ambient temperature due to both internal heating and external heat (sun) load.
These high overload resistant chips run with fairly high voltages and hence have significant internal power dissipation.
The temp on the chip in a Preamp during the heat of Summer can be expected to be well in excess of 100 deg (F).

If a Preamp is not used, then the temperature of the first RF chip in the HDTV's tuner determines the thermal noise floor.
Since HDTVs run hot inside the box, I would figure the temp on the chip is in excess of 100 deg (F) after allowing for chip/air thermal resistance.

Fortunately, Winter to Summer temperature fluctuations typically result in less than a dB difference in sensitivity.

See the fol. Maxim App Notes for the NF/Sensitity equation I cited above, as well as further information on how
thermal noise levels, Cascaded Noise Figures and Noise Factors are calculated:
http://www.maxim-ic.com/appnotes.cfm...te_number/1836
http://www.maxim-ic.com/appnotes.cfm...te_number/2875
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post #356 of 433 Old 10-23-2005, 05:32 AM
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holl_ands,

The ambient temperature of a preamp or first stage of a receiver has nothing to do with receiver sensitivity. Only preamp (or first stage) Noise Figure, effective antenna temperature (not it's physical temperature, but the noise temperature of what the main lobe is pointed at) and feedline loss effect receiver sensitivity in the following way:

Noise Power = 10 log KBTs

K = 1.38x10E-23
B = bandwidth in Hz
Ts = receive system noise temperature

Ts = Ta + (Lr - 1)Tl + LrTr

Ta = antenna temperature
Lr = feedline loss (as a ratio)
Tl = physical temperature of feedline (290K)
Tr = receiver noise temperature

Tr = 290(10^(f/10) - 1)

f = Noise Figure

The above equations work for any receive system, whether the antenna is pointed at cold sky (satellite systems) or on the horizon (terrestrial systems).

When the antenna is pointed at the horizon, the effective antenna temperature is 290K. At the same time, NF is a function of 290K. When Ta is 290K, the equation can be simplified to:

-106.2 dBm + NF (at 6 MHz bandwidth).

Expressing preamp noise performance in NF is just a mathematical short cut when you know the antenna is pointing on the horizon. This is why satellite preamps are never specified in NF, but always in noise temperature.

Ron

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post #357 of 433 Old 10-23-2005, 09:01 AM
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Ron,
The info on receiver noise is what I tried to express and if I did the Math right what it means for receiver sensitivity. I think the question of a UHF TV antenna's noise temperature is more interesting. Only half of the antenna's main lobe is aimed at the ground and the other half is aimed at the sky, also it only responds to horizontally polarized signals so it will see much less than the 290 deg. noise power from the ground. I found these measurements, that are in the UHF range http://www.its.bldrdoc.gov/pub/ntia-...90/chap1&2.pdf If I understand the plots at the high end and in rural areas a temperature of around 70 deg. K was measured. John
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post #358 of 433 Old 11-18-2005, 08:00 AM
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Quote:
Originally Posted by John Mason View Post

Thanks for another of your exhaustive reports, holl_ands. Probably not digesting the final 'graphs enough, but the test conclusions seem contradictory: it outperformed the Zenith/LG yet couldn't handle short-delay signals, which presumably made the LG design so good at Mark Schubin's heavy-multipath NYC location.

(Also, at a NYC location here, only ~9 blocks from NYC's transmitter, but with no view of it, only reflections, and can't tune any HD signals reliably with a Silver Sensor and an early-generation tuner built into my year-2000 Philips RPTV. Yup, not a good combination. But the still-unavailable Zenith/LG combo sounded promising--even here.) Rely on two cable subscriptions. -- John

I've been using one of the Radio Shack (Accurian) STBs currently on close-out at RS. I'm 20 blocks north of the ESB, facing north, and it picks up almost everything except 13 (61). Has anyone reliably determined what generation decoder is in this RS STB?

Early Panasonic and RCA STBs would work, but they were very sensitive to antenna location and orientation, and usually only picked up 2 (56) and 5 (44).
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post #359 of 433 Old 11-18-2005, 09:15 AM
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Quote:
Originally Posted by hphase View Post

I've been using one of the Radio Shack (Accurian) STBs currently on close-out at RS. I'm 20 blocks north of the ESB, facing north, and it picks up almost everything except 13 (61). Has anyone reliably determined what generation decoder is in this RS STB?

I'd like to know, too, just out of curiosity. I'm in a difficult reception area (more fringe than multipath) and my Accurian is markedly better than the old SIR-T151 I had before.

In fact, I'm close to buying either a Phillips plasma or Samsung DLP with built-in tuner, and I hope the tuners in there are as good as the Accurian's, because I need every ounce of reception power I can get.

BTW, great work holl_ands and others... It is much appreciated.
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post #360 of 433 Old 11-18-2005, 12:00 PM
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My unscientific tests have shown the Radio Shack unit is much better than earlier STBs "in the city" (lots of signal, lots of ghosts) and about as good as earlier units "in the country" (less signal and a lot less ghosts.) City reception is with a silver sensor and country reception is with a big antenna on the roof, both of which are typical scenarios for OTA reception, both NTSC and ATSC.
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