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When Directv goes all mpeg4 will they still use 101,110 and 119?


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#81 OFFLINE   HoTat2

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Posted 05 March 2014 - 11:39 AM

it's reverse using uplink/downlink chunks of spectrum

I think "reverse" in this context refers to the transponder signal polarity schema .

 

Instead of the normal even numbered tps. which use H/LHCP, and the odd tps. that use V/RHCP for both up- and down-links. It's H/LHCP for the odd and V/LHCP for the even.   


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#82 OFFLINE   HoTat2

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Posted 05 March 2014 - 12:11 PM

Is DBS Ku spacing still 9* or is it officially 4.5*? Are those "tweener" slots at 105.5 and 114.5 operational? Even at 2* versus 4.5* that seems like a big difference for a 1.5cm vs 2.5cm wavelength difference...

 

Higher frequencies offering more gain for a given dish size is great and all, but if your signal and your noise (i.e. nearby slots owned by others) are both at the same frequency you don't derive any benefit from the higher gain in terms of interference from your "neighbors", do you?

 

If that's the case, is the closer spacing of Ka a result of the smaller wavelength somehow reducing such interference from nearby slots? If so, that benefit would have to compensate for the negative of geometry (i.e. the view to the sky of for example 101/110/119 in Bangor vs San Diego) enough to allow closer spacing. If Directv used a toroidal dish and installation allowed/required adjusting the LNB spacing I could understand it, but they don't, they use a one size fits all dish across all of CONUS.

 

Would it have helped reduce spacing requirements if the FCC/ITU staggered polarity assignments on every other slot? For example, if they wanted 1* spacing for a certain frequency block, using H/V polarization on even slots and circular polarization on odd slots. I know RF is still RF regardless of polarity, and perhaps I simply don't know enough about how this all works to make this suggestion, but I can't help wondering if this would allow for a way to better distinguish your RF from "their" RF in the design of a dish/LNB.

From my knowledge of it;

 

The greater dish aspect ratio (D/wavelength) of the dish for Ka band frequencies increases the dish's directivity (i.e. it narrows its beamwidth) which reduces co-channel interference from adjacent slots permitting the closer spacing of neighboring co-frequency satellites for the same level of interference (or "C/I" ratio) compared to the Ku DBS band.

 

As to satellite arc perspective from a given location, I gather such close spacing of the satellites as DIRECTV has from only 99-103 degrees, is seen by a customer's ODU as a virtual single slot at 101 degrees no matter the viewing angle in the CONUS, Alaska, or Hawaii.

 

For instance, notice how the same LNBF (and thus same feedhorn spacing) for the 1.2m Al/Hi dish can be used in either the mainland U.S. or Hawaii which is over 2500 mi. away from the mainland's west coast.           


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#83 OFFLINE   slice1900

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Posted 05 March 2014 - 03:47 PM

From my knowledge of it;

 

The greater dish aspect ratio (D/wavelength) of the dish for Ka band frequencies increases the dish's directivity (i.e. it narrows its beamwidth) which reduces co-channel interference from adjacent slots permitting the closer spacing of neighboring co-frequency satellites for the same level of interference (or "C/I" ratio) compared to the Ku DBS band.

 

As to satellite arc perspective from a given location, I gather such close spacing of the satellites as DIRECTV has from only 99-103 degrees, is seen by a customer's ODU as a virtual single slot at 101 degrees no matter the viewing angle in the CONUS, Alaska, or Hawaii.

 

For instance, notice how the same LNBF (and thus same feedhorn spacing) for the 1.2m Al/Hi dish can be used in either the mainland U.S. or Hawaii which is over 2500 mi. away from the mainland's west coast.           

 

I agree the geometry doesn't matter for 99/101/103, but I specifically mentioned 101/110/119. Unless Directv drops 110/119 from customer use in the future, the geometry for those still matters. So what happens if/when there are DBS satellites at 105.5 and 114.5? I would think the geometry could make that an issue, and if not it's close.

 

Close enough that Directv doesn't make a 5LNB for the AK/HI dish. If those customers want 119, they have to use a second 1.2m dish, so the geometry must be off by enough between HI and the rather large range of possible locations in AK that they can't place 101 and 119 LNBs in such a way that both will work for all locations in both states.


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#84 OFFLINE   P Smith

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Posted 05 March 2014 - 04:00 PM

they cannot make unified dish for add 95W (it's 6 degree spacing) not telling the non-existing sat at 105.5W



#85 OFFLINE   slice1900

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Posted 05 March 2014 - 05:50 PM

they cannot make unified dish for add 95W (it's 6 degree spacing) not telling the non-existing sat at 105.5W

 

I thought spacing wasn't the only reason there's no SL6, but also because it isn't circularly polarized like the rest and it wouldn't be possible to align a single dish that had 99/101/103/110/119 and added a 95 H polarized LNB?

 

Anyway, I wasn't suggesting geometry issues in making a dish that receives 101 and 105.5, but that someone else's 105.5 sat could interfere with Directv's reception from 101 and/or 110 in certain locations because the SL5 has fixed LNB spacing even though the spacing of the satellites in the sky is variable depending on where in the US you're located.

 

If Directv wanted to add 95 (or 105.5) to the Slimline and didn't mind changing its design to do so, I would think changing the curvature of the reflector to move the focal point further away and using a longer LNB arm would allow for more room between the individual LNBs and resolve the spacing issue.


Edited by slice1900, 05 March 2014 - 05:51 PM.

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#86 OFFLINE   harsh

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Posted 06 March 2014 - 08:36 AM

So?  Doesn't really have anything to do with my comment.  Higher power increases EIRP, it doesn't change the gain of a dish.

The implication was that all that was needed was a slightly bigger dish, but clearly that's not the case. More power and better weather are apparently also required.

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#87 OFFLINE   Diana C

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Posted 06 March 2014 - 05:11 PM

The implication was that all that was needed was a slightly bigger dish, but clearly that's not the case. More power and better weather are apparently also required.

Hmmm...seems like you infered something I did not mean.  What I said, speaking about Ka signals, was: "the shorter wavelength also means that a dish of a given size will provide more gain for Ka than for Ku, all else being equal."  That is not to say that Ka can reliably be used for DTH transmission ONLY by virtue of that additional gain, it also takes higher transmitter power.


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#88 OFFLINE   HoTat2

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Posted 06 March 2014 - 05:32 PM

Yep;

 

The implication was not the higher dish gain at Ka frequencies would necessarily directly offset the need for any higher transmitter power, but would certainly help mitigate the level of power increase needed.  


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#89 OFFLINE   ejbvt

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Posted 06 March 2014 - 09:35 PM

I hope they dont stop braodcasting thier SD stuff... Some of us DO NOT LIKE HD and dont want to pay for it!!

 

You probably saw a poorly set up in-store display or Dish Network. There is absolutely positively no way you would say that about a properly set up HDTV. 


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#90 OFFLINE   JosephB

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Posted 18 March 2014 - 09:55 PM

Just my two cents:

 

DirecTV went with Ka because they had it, and they put the HD on Ka instead of Ku, because if you're rolling out a new service, you put it on the new frequencies. Would have been monumentally stupid to try to put HD on Ku and move SD to Ka, necessitating a total swap of the entire install base. There's no reason HD can't (and won't) be on Ku eventually, frequency band and encoding (not modulating) schemes are completely independent.

 

And you'll know when DirecTV is about to start the transition, it'll be around two years after the date they stop installing new 101-only dishes and SD only set tops. As long as they're still installing 101 only dishes or SD only set tops, then the transition is a very long way away. They might still get away with 101-only dishes, if they were going to do a flash cut, but they will have to replace every single SD only set top box with an HD capable receiver, even if it's downconverting for an SD TV set, before they can move to all MPEG-4. Because at that point, what would be the point of having MPEG-4 SD only boxes and duplicating all that bandwidth. If you're going to distribute all those MPEG-4 boxes, might as well make them capable of decoding and downconverting HD and then you can drop half the encoders at the broadcast center, open up a TON of bandwidth, reduce the number of boxes you support, eliminate an installation call when a customer upgrades their TV, etc. 



#91 OFFLINE   P Smith

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Posted 18 March 2014 - 10:20 PM

they using Ka for HD because they must use Ka; because no bandwidth on Ku tpns for HD

 

it's much simpler then your convoluted  logic :)



#92 OFFLINE   JosephB

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Posted 19 March 2014 - 09:02 AM

they using Ka for HD because they must use Ka; because no bandwidth on Ku tpns for HD

 

it's much simpler then your convoluted  logic :)

 

Right, that's exactly what I said. Someone asked why not use Ku, or could they use Ku? Sure. The band used has nothing to do with the encoding scheme. Just 1s and 0s. They used Ka because that's what they had available, and it makes more sense than moving existing services around.



#93 OFFLINE   Diana C

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Posted 19 March 2014 - 01:07 PM

...it's much simpler then your convoluted logic :)

 

 

Seems to me that...

 

DirecTV went with Ka because they had it, and they put the HD on Ka instead of Ku, because if you're rolling out a new service, you put it on the new frequencies....

 

is saying the same thing as....

they using Ka for HD because they must use Ka; because no bandwidth on Ku tpns for HD

 

Nothing convoluted about it.


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#94 OFFLINE   P Smith

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Posted 19 March 2014 - 01:22 PM

castrated presentation of original post to which I did reply make it unethical argument directed to a person :(, what actually must be adhere to the topic as I'm been reminded



#95 OFFLINE   Diana C

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Posted 19 March 2014 - 04:19 PM

I think it is time to let this thread fade away.


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#96 OFFLINE   harsh

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Posted 21 March 2014 - 07:59 AM

And you'll know when DirecTV is about to start the transition, it'll be around two years after the date they stop installing new 101-only dishes and SD only set tops.

You'll know DIRECTV is on the move when they offer an MPEG4/8SVX/DVB-S2 box that has an RF modulator built in.

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#97 ONLINE   longrider

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Posted 21 March 2014 - 09:50 AM

You'll know DIRECTV is on the move when they offer an MPEG4/8SVX/DVB-S2 box that has an RF modulator built in.

I dont see that happening.  Most any SDTV since about 1990 (other than the most basic, economy units) will have a composite in.  My expectation would be that the techs would have external RF modulators on hand for when it is needed as it would be cheaper to do that than build into the boxes where one of a hundred might actually use it.


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#98 OFFLINE   HoTat2

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Posted 21 March 2014 - 10:27 AM

You'll know DIRECTV is on the move when they offer an MPEG4/8SVX/DVB-S2 box that has an RF modulator built in.

Lost me here;

 

Why the mention of "8SVX?" :confused:

 

You mean the old "8 bit Sampled Voice" format originally developed for Commodore-Amiga computers back in the '80s? 


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#99 OFFLINE   Diana C

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Posted 21 March 2014 - 10:28 AM

Perhaps he meant 8PSK?


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#100 OFFLINE   P Smith

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Posted 21 March 2014 - 10:32 AM

for the whole shabad "MPEG4/8SVX/DVB-S2" DTV is using own designators like "DSS-3" for transponders or "A3" for channels






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