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DirecTV National HD Listing/Maps Discussion Thread (Technical - Not Anticipation)


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#326 OFFLINE   harsh

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Posted 08 July 2012 - 02:08 PM

Fanboyism aside, how is it that DIRECTV is only managing to wring 5-6 channels out of 36MHz of satellite bandwidth?

The answer (nor understanding thereof) has nothing to do with what provider anyone subscribes (or doesn't subscribe) to so there's really no need to visit there.

For reference, Blu-ray is around 24MHz.

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#327 OFFLINE   veryoldschool

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Posted 08 July 2012 - 02:20 PM

Fanboyism aside, how is it that DIRECTV is only managing to wring 5-6 channels out of 36MHz of satellite bandwidth?

The answer (nor understanding thereof) has nothing to do with what provider anyone subscribes (or doesn't subscribe) to so there's really no need to visit there.

For reference, Blu-ray is around 24MHz.

This makes no sense.
As for 5-6 HD channels per 36 MHz BW, it has everything to do with the modulation type they're using.
"For example" if it was the same as ATSC, then it would manage easily 6-7, 19.2 Mb/s channels.
A.K.A VOS

#328 OFFLINE   Sixto

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Posted 08 July 2012 - 02:24 PM

Fanboyism aside, how is it that DIRECTV is only managing to wring 5-6 channels out of 36MHz of satellite bandwidth?

The answer (nor understanding thereof) has nothing to do with what provider anyone subscribes (or doesn't subscribe) to so there's really no need to visit there.

For reference, Blu-ray is around 24MHz.

The key isn't as much the MHz as the data bandwidth per transponder, which is about 38Mbps as best we can tell. The translation form MHz to Mbps depends on the engineers desire for quality considering weather and the technology available, along with the type of transponder/license (Ka).
DirecTV: Genie HR44, H25, CCK, GenioGo, SWiM-16 & SWiM-8, DECA to Gigabit Switch with FiOS (75/75)
FiOS: Roamio Pro's (2), Roamio Plus, Mini's (4) with Ultimate HD (My Roamio Thoughts)

#329 OFFLINE   veryoldschool

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Posted 08 July 2012 - 02:29 PM

The key isn't as much the MHz as the data bandwidth per transponder, which is about 38Mbps as best we can tell. The translation form MHz to Mbps depends on the engineers desire for quality considering weather and the technology available, along with the type of transponder/license (Ka).

Each type of modulation has its pros & cons and another example is my U-who that has 64 Mb/s while using 7.5 MHz BW.
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#330 OFFLINE   Sixto

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Posted 08 July 2012 - 02:36 PM

Each type of modulation has its pros & cons and another example is my U-who that has 64 Mb/s while using 7.5 MHz BW.

Exactly, and in this specific D1x case they're currently at 38Mbps as best we've calculated.
DirecTV: Genie HR44, H25, CCK, GenioGo, SWiM-16 & SWiM-8, DECA to Gigabit Switch with FiOS (75/75)
FiOS: Roamio Pro's (2), Roamio Plus, Mini's (4) with Ultimate HD (My Roamio Thoughts)

#331 OFFLINE   veryoldschool

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Posted 08 July 2012 - 02:38 PM

Exactly, and in this specific D1x case they're currently at 38Mbps as best we've calculated.

Someone with a Spectrum Analyzer would be able to measure the BW.
A.K.A VOS

#332 OFFLINE   Sixto

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Posted 08 July 2012 - 02:40 PM

Someone with a Spectrum Analyzer would be able to measure the BW.

Yep, I haven't myself but others have.
DirecTV: Genie HR44, H25, CCK, GenioGo, SWiM-16 & SWiM-8, DECA to Gigabit Switch with FiOS (75/75)
FiOS: Roamio Pro's (2), Roamio Plus, Mini's (4) with Ultimate HD (My Roamio Thoughts)

#333 OFFLINE   veryoldschool

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Posted 08 July 2012 - 02:49 PM

Yep, I haven't myself but others have.

A couple of differences between ATSC and the SAT modulation is my TV needs more than 13 dB SNR to stay locked without errors, while the SAT works down to about 8 dB CNR.
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#334 OFFLINE   georule

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Posted 08 July 2012 - 09:08 PM

Hardware vendors have been known to gild the lily, certainly. . . but if you take the presentation seriously (and the presentation was not produced by DirecTV), 6Mbps x 6 = 36Mbps. Pg 27/28. As Sixto notes above, best calculations have the newest D* birds at 38Mbps per TP. Those calculations took place *before* the latest move to 6 HD per TP, so cannot be accused of trying to reach a pre-determined result to fit a theory.

So, you can bag on D* all you like, and cry "fanboy!" to your heart's content, but it isn't just D* saying this is possible with the latest/greatest encoders; it is also Ericsson.

Therefore, before you start doing the fanboy j'accuse, you better either disprove 38Mbps, or go after Ericsson credibly as liars.

Edited by georule, 08 July 2012 - 09:22 PM.

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#335 OFFLINE   cypherx

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Posted 09 July 2012 - 08:01 AM

A couple of differences between ATSC and the SAT modulation is my TV needs more than 13 dB SNR to stay locked without errors, while the SAT works down to about 8 dB CNR.


Wow what modulation rate works down to 13 dB SNR? 256QAM has a MINIMUM of 32 dB and that's 38.8mbps in a 6 MHz wide channel. Helps when cable is a closed system though. I've had SNR's as high as 40 before on DOCSIS channels, though they hover around 37, 38.

- > Link to my setup thread< -

My  DirecTV HD WISHLIST:  NickJR, Nicktoons, Revolt.TV, FXM, We, Oxygen, The Hub, Fuse, GSN, Sprout, GAC, Esquire, BBC World News, Sundance, Up, Music Choice Play HD, Al Jazeera America, Military Channel, NASA

My DirecTV SD WISHLIST: MTV Hits, MTV Jams, Music Choice, Youtoo TV

 

---

HR44-500
HR24-200

 


#336 OFFLINE   veryoldschool

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Posted 09 July 2012 - 08:31 AM

Wow what modulation rate works down to 13 dB SNR? 256QAM has a MINIMUM of 32 dB and that's 38.8mbps in a 6 MHz wide channel. Helps when cable is a closed system though. I've had SNR's as high as 40 before on DOCSIS channels, though they hover around 37, 38.

OTA needs to work with weaker signals, than a CATV system.
My OTA can be as high as 28-30 dB SNR.

My U-Who runs at 28-29 dB "noise margin", but their minimum is around 12 dB, and maybe even 9 dB.
A.K.A VOS

#337 OFFLINE   doctor j

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Posted 11 July 2012 - 11:17 AM

Someone with a Spectrum Analyzer would be able to measure the BW.


I think someone has and previously reported.

http://www.dbstalk.c...05&postcount=95

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#338 OFFLINE   veryoldschool

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Posted 11 July 2012 - 11:18 AM

I think someone has and previously reported.

http://www.dbstalk.c...05&postcount=95

Doctor j

Yep, it wouldn't have been his first time.
Would have been nice if that linked post had a link to the measured bandwidth.
A.K.A VOS

#339 OFFLINE   P Smith

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Posted 11 July 2012 - 12:02 PM

Yep, it wouldn't have been his first time.
Would have been nice if that linked post had a link to the measured bandwidth.


check this post ;)
http://www.dbstalk.c...42&postcount=79

#340 OFFLINE   veryoldschool

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Posted 11 July 2012 - 12:43 PM

check this post ;)
http://www.dbstalk.c...42&postcount=79

Being who I am, I'm more interested in MHz than Mb/s
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#341 OFFLINE   P Smith

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Posted 11 July 2012 - 02:10 PM

Being who I am, I'm more interested in MHz than Mb/s


Ah, that's in FCC docs.

#342 OFFLINE   cypherx

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Posted 11 July 2012 - 02:12 PM

I thought it was 36 MHz.. but per chance the Spaceways *MAY* have bandwidths as much as 62.5 MHz.

- > Link to my setup thread< -

My  DirecTV HD WISHLIST:  NickJR, Nicktoons, Revolt.TV, FXM, We, Oxygen, The Hub, Fuse, GSN, Sprout, GAC, Esquire, BBC World News, Sundance, Up, Music Choice Play HD, Al Jazeera America, Military Channel, NASA

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---

HR44-500
HR24-200

 


#343 OFFLINE   veryoldschool

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Posted 11 July 2012 - 02:15 PM

I thought it was 36 MHz.. but per chance the Spaceways *MAY* have bandwidths as much as 62.5 MHz.

Both sound "about right".
A.K.A VOS

#344 OFFLINE   P Smith

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Posted 11 July 2012 - 02:15 PM

I thought it was 36 MHz.. but per chance the Spaceways *MAY* have bandwidths as much as 62.5 MHz.


FCC docs stats 36 MHz for Ka sats of D## series. IMO, SW could have 70 or 80 MHz tpns, but we have no docs to support that by facts.

#345 OFFLINE   doctor j

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Posted 11 July 2012 - 02:39 PM

FCC docs stats 36 MHz for Ka sats of D## series. IMO, SW could have 70 or 80 MHz tpns, but we have no docs to support that by facts.


Documents here:

http://licensing.fcc...erC/File Number

Go to "Attachment Menu" Then "Exhibit D"

I've copied a segment from page #11

"When the satellite is operated in the non-processor mode it can be viewed as supporting 8 contiguous 62.5 MHz channels"

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#346 OFFLINE   P Smith

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Posted 11 July 2012 - 02:47 PM

More interesting facts:

The satellite also includes wideband (i.e., 165 MHz) uplink and downlink channels

The emission designators of the signals to be transmitted through these channels are: 24M0G7W, 36M0G7W and 54M0G7W with associated allocated bandwidths of 24 MHz, 36 MHz and 54 MHz, respectively.

The downlink antenna for the 19.7-20.2 GHz band is a 1500 element active phased array. This array is extremely flexible and can be configured from the ground to create up to twenty-four 0.5° spot beams, a single wide area CONUS beam, or virtually any beam combination in between these two extremes.


Edited by P Smith, 11 July 2012 - 03:23 PM.


#347 OFFLINE   veryoldschool

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Posted 11 July 2012 - 03:09 PM

The downlink antenna for the 19.7-20.2 GHz band is a 1500 element active phased array. This array is extremely flexible and can be configured from the ground to create up to twenty-four 0.5° spot beams, a single wide area CONUS beam, or virtually any beam combination in between these two extremes.

While phased array can be quite flexible, The CONUS beam testing didn't turn out to be too successful.

In the end, measuring what bandwidth DirecTV is actually using might be of more use.
A.K.A VOS

#348 OFFLINE   P Smith

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Posted 11 July 2012 - 03:16 PM

Last time ( it was a few years ago) I posted these pictures ... don't recall measurements...

Just fired my SA PSA-37D ... 35..36 MHz per tpn in a range 250...750 MHz range.

#349 OFFLINE   veryoldschool

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Posted 11 July 2012 - 03:20 PM

Last time ( it was a few years ago) I posted these pictures ... don't recall measurements...

Just fired my SA PSA-37D ... 35..36 MHz per tpn in a range 250...750 MHz range.

Thanks, and I knew you'd done it before.
So now we have "facts". :)

So now that we know the BW is 36 MHz, if this is only getting 38 Mb/s, it must be using the worst modulation technique known to man.

I'm by no means an expert on types of modulation but if it's only 1 Mb/s/MHz this sounds basically primitive analog, which we know it isn't.

Edited by veryoldschool, 11 July 2012 - 03:31 PM.

A.K.A VOS

#350 OFFLINE   charlie460

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Posted 11 July 2012 - 07:37 PM

I would be curious to know what bitrate and whether or not they are using the new encoders for the Audience Network. The picture quality is quite bad on tonight's Damages premiere. Lots of artifacting.




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