ATSC Tuner & Demodulator Chipsets - News, Discussion

[stampeder]

For those not familiar with the term, a Can or CAN tuner is a separate tuner chip surrounded by a metal shield (a chip in a can - a can of tuna and a canned tuner - get it?). These have been common on computer PCI TV cards and consumer TVs since the mid-1990s.

The newer technology consists of an entire TV tuner in one small form factor, such as for a USB device. With the Mobile DTV revolution in progress these devices are now coming to the forefront for their many advantages.

There's a very good summary in that article of the main differences between the Can type of DTV Tuner chips used earlier and those new ones sweeping over the industry:

Unlike traditional bulky CAN tuners, silicon tuners can address the problems surrounding signal reception quality and tuner performance. In addition to delivering better user experience applications, silicon tuners enable thinner TV board architectures to meet consumer demand for thinner and flatter TV screens.

[stampeder]

I have a whack of tuner cards here, and only the Xc5000 equipped HVR-950Q can pick up the WNPI-DT PBS station from far far away.

To corroborate what mlord was saying, here's an article that points out the main features of Silicon tuners:

http://www.techonline.com/product/un...hood/208801325

[holl_ands]

There may be some Silicon Tuners that are more sensitive than the better "Tin Can" tuners,
but the much hyped "double conversion" Microtune MT2131 silicon tuner in the Tivo HD-DVR,
and a few CECBs (e.g Sansonic, Lasonic & DTVPalPlus) did not exhibit any significant
improvement in sensitivity vs conventional "Tin Can" tuners...indeed, I have seen a few
reports where they had difficulty in high signal environments (a double conversion weakness),
which is ironic, given Microtune's claim that numerous CECB boxes didn't meet specs.

BTW: A comparison test on a single frequency is insufficient to "compare" tuner sensitivities....
That particular freq may be more sensitive or a better VSWR match, but elsewhere it could be worse....

[stampeder]

I would add that in my own particular situation my 2 pcHDTV CAN cards (with Generation 5 LG DT3303 tuners) perform a bit better than my 3 USB devices (2 950Qs with Xceive XC5000 tuners, and a single 950 with Xceive XC3028 tuner) so clearly there are many considerations at play when comparing.

[mlord]

Originally Posted by stampeder

I would add that in my own particular situation my 2 pcHDTV CAN cards (with Generation 5 LG DT3303 tuners) perform a bit better than my 3 USB devices (2 950Qs with Xceive XC5000 tuners, and a single 950 with Xceive XC3028 tuner) so clearly there are many considerations at play when comparing.

All of those devices use silicon tuners and/or demods, so no surprises there. Though it would be very interesting to know what is inside the "can" on that pcHDTV board. The LG DT3303 is not a tuner chip --> it's a demodulator/decoder chip. It is often paired with a silicon tuner such as the Xc3028 inside the "can".

A "can" tuner, in the sense that the quoted articles use the term, refers to a sealed metal enclosure (the "can"), containing tuner circuitry built up from many discrete, and mainly "analog", components. Lots of hand-tuned chokes, coils, and variable capacitors/inductors, op-amps, individual transistors, and the like.

The volume inside the "can" is often mechanically divided into several shielded sections for different stages of the RF receiver circuitry.

With a silicon tuner, nearly all of that stuff just "goes away". There may or may not still be a (much smaller) "can" enclosure for the tuner chip and its pre-amp, but that's not a "can" tuner in the sense used in the articles.

Look at an HVR-1600 card, for example. It has a large, traditional analog "can" tuner at the top, and a much smaller "can" between that and the PCI edge connector. That second, smaller "can", holds the silicon tuner chip, and possibly the demodulator chip, plus glue, for ATSC reception.

One of my PVR-250 cards (traditional analog "can" tuner) had trouble receiving the analog PBS station we used to get here. I pried the lid off of the "can", and adjusted some of the coils until reception was near perfect.

With a silicon tuner, that kind of issue shouldn't happen, but if it did, a software adjustment would be how it would get corrected.

Cheers

[stampeder]

Originally Posted by mlord

it would be very interesting to know what is inside the "can" on that pcHDTV board. The LG DT3303 is not a tuner chip --> it's a demodulator/decoder chip. It is often paired with a silicon tuner such as the Xc3028 inside the "can".

Keep in mind that the pcHDTV 5500 is a combo NTSC/ATSC/QAM card:

(image from http://www.pchdtv.com)

Without prying open the can, it is labeled "TDVS-H064F" and peeling away the pcHDTV sticker reveals the LG logo embossed into the can's metal surface. This is the LG NTSC Analogue tuner. To the right of the can, the surface-mounted chip is the Conexant CX23883 Broadcast Decoder. Here is what dmesg shows for the pcHDTV card's frontend:

DVB: registering adapter 0 frontend 0 (LG Electronics LGDT3303 VSB/QAM Frontend)...

I do not enable the NTSC Analogue tuners on my system. Instead I run 2 Hauppauge 150 PCI cards for Analogue since their performance is so much better.

To fully support the ATSC/QAM side of the pcHDTV card in the Linux kernel the following modules get loaded: cx8800, cx8802, cx88-dvb, cx88xx, and cx88-alsa, so its an LG frontend integrated with Conexant video and audio decoding. Here's what lspci -v shows for the first pcHDTV card:

01:00.0 Multimedia video controller: Conexant Systems, Inc. CX23880/1/2/3 PCI Video and Audio Decoder (rev 05)
        Subsystem: pcHDTV pcHDTV HD-5500                                                                      
        Flags: bus master, medium devsel, latency 64, IRQ 16                                                  
        Memory at f8000000 (32-bit, non-prefetchable) [size=16M]                                              
        Capabilities: [44] Vital Product Data                                                                 
        Capabilities: [4c] Power Management version 2                                                         
        Kernel driver in use: cx8800                                                                          
        Kernel modules: cx8800                                                                                

01:00.2 Multimedia controller: Conexant Systems, Inc. CX23880/1/2/3 PCI Video and Audio Decoder [MPEG Port] (rev 05)
        Subsystem: pcHDTV pcHDTV HD-5500                                                                            
        Flags: bus master, medium devsel, latency 64, IRQ 16                                                        
        Memory at f7000000 (32-bit, non-prefetchable) [size=16M]                                                    
        Capabilities: [4c] Power Management version 2                                                               
        Kernel driver in use: cx88-mpeg driver manager                                                              
        Kernel modules: cx8802                                                                                      

01:00.4 Multimedia controller: Conexant Systems, Inc. CX23880/1/2/3 PCI Video and Audio Decoder [IR Port] (rev 05)
        Subsystem: pcHDTV pcHDTV HD-5500                                                                          
        Flags: bus master, medium devsel, latency 64, IRQ 10                                                      
        Memory at f6000000 (32-bit, non-prefetchable) [size=16M]                                                  
        Capabilities: [4c] Power Management version 2

The two Hauppauge 950Q USB devices, with their Xceive XC5000 tuners, require only the au0828 module. I put the following line into /etc/modprobe.conf as a tweak for some tuning problems I've been having with them. It forces the tuner to stay alive at all times:

options xc5000 no_poweroff=1

Lastly, the single Hauppauge 950 USB device with the Xceive XC3028 tuner requires the following kernel modules: em28xx, em28xx-dvb, em28xx-alsa, tuner_xc2028

[holl_ands]

pcHDTV HD-5500 has an LG Half-NIM "TIN-CAN" tuner plus a Conexant CX23883:
http://picasaweb.google.com/Trinitro...92369561439394

Conexant CX23883 is a high speed signal processor chip that takes the IF signal
(Intermediate Frequency RF) from the TIN-CAN tuner and demodulates
NTSC (Analog) signals for transfer to the host PC:
http://www.conexant.net/servlets/Dow...id=193&revid=4

LG TIN-CAN tuner part number wasn't visible, but is probably same/similar to TDVS-H066F Half-NIM:
http://www.haluyatech.com/down/lgtunner/TDVS-H066F.pdf
It's clearly a single conversion (vice double conversion) tuner, probably NOT a silicon tuner,
plus LGDT3303 "5th Gen" ATSC/QAM Decoder Chip (CECB's use much higher performance 6th Gen):
http://cn.lginnotek.com/bin/product/...l_inquire.html
PS: I've seen better Noise Figure specs on some CECB TIN-CAN tuners.....
Also note H066F spec is dated Aug2006....

[stampeder]

Ya, the pcHDTV 5500 is getting long in the tooth and is somewhat equivalent to Fusion Gold cards. Jack Kelliher has been asked many times if he intends to offer a new PCI-e model based on the latest chipsets, but he hasn't promised anything.

I keep using the pcHDTV 5500 cards because their performance is very reliable and they will never process the crazy Broadcast Flag if it is ever implemented.

[AudioBob]

The helpful rep from Channel Master says that the input dynamic of the CM-7000 is -83 to -5dBM with a sound noise ratio of -15dBM. He also says he is personally unaware of any TV tuners that better the sensitivity of the CM-7000.
Any opinions?

[CamDAB]

Originally Posted by AudioBob

He also says he is personally unaware of any TV tuners that better the sensitivity of the CM-7000.

Funny you should mention this.

I just recently compared our 19" Toshiba 19AV600U (going by memory now on the TV model number...) with my CM-7000 and the CM-7000 won hands down on reception of certain channels. I carried my indoor mounted 4221HD antenna into the room with the TV and took the CM box too. From our location, the TV didn't get 36.1 or 44.1 at all. The CM box got both solid with about roughly 75% signal. But, and here's the other issue, on Global, (41.1) the TV won hands down. The CM box was pixellating all over the place with audio dropouts, the TV was solid. Both registered 100% signal. My conclusion was that the CM is very sensitive to data stream errors of some sort. Last week I had Tuesdays, Wednesdays and Thursdays Coronation Street (on CBC) all with really bad pixel / sound breakup. Monday and Friday were 100% error free. And CBC normally is the strongest station I get with no errors at all. CM can't seem to put their finger on the problem, as I'm on a second box that does the same thing....

Go figure....

Cameron

[holl_ands]

Since the sensitivity of any particular model varies by 1 or 2 dB from unit to unit, it is very difficult to
draw any conclusions re whether one design is inherently superior to another.

NAB sponsored a CECB test, finding that the actual number of "missed" OTA channels did not directly
correlate to either the measured sensitivity nor how many ATSC A-74 Ensemble RF Captures failed:
http://www.nabfastroad.org/NAB-STV%2...report.doc.pdf
An important degradation factor NOT quantified was VSWR mismatch on each channel, which could
have been the overwhelming problem on some channels in addition to sensitivity and multipath:
http://www.digitalhome.ca/forum/showthread.php?p=855224

CM7000 had better than average sensitivity and fewer number of failed Ensembles (2 vice 3),
but "missed" more channels than TEN other CECBs. So bear in mind: YMMV from box to box.....

[ProjectSHO89]

The helpful rep from Channel Master says that the input dynamic of the CM-7000 is -83 to -5dBM with a signal/noise ratio of -15dBM. He also says he is personally unaware of any TV tuners that better the sensitivity of the CM-7000.
Any opinions?

Those just happen to be the minimum specs that were in place for all the CECBs...

The 15 (rounded) dB S/N ration is the ATSC specification for all compliant tuners.

[snowman53]

I am in a fringe area about 30 mi south of the San Diego towers in Baja Ca Mx and need all the signal sensitivity I can get. Any recommendations on which set top boxes and PC cards offer the best sensitivity?

Thanks!

[goforit]

Compared to my 2009 Samsung, and 2010 Toshiba TVs/tuners, my 2009 LG TV/tuner seems to have the best tuner- it gets a 24/7 lock on my one weak/distant station that the others can't.

[stampeder]

Recent posts about these devices have been moved into their own thread in the HTPC Forum where other threads exist concerning them:

http://www.digitalhome.ca/forum/showthread.php?t=121224

This existing thread is for news and technical info about ATSC chipsets as they are designed and operate, regardless of the consumer product in which they appear.