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DIRECTV Satellite Discussion D-14 @99W


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#151 OFFLINE   veryoldschool

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Posted 13 August 2011 - 11:28 AM

With sufficiently large dishes at the uplink site, I have no worries they can avoid interference with a satellite 2 degrees away.

Think DirecTV has that covered:
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#152 OFFLINE   harsh

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Posted 13 August 2011 - 12:19 PM

2 degree spacing works on C band where the -3 db point on a standard 10' dish is much wider than a KU dish, and KA is even narrower (note the fine tuning adjusters needed for KA band?).

C-band isn't scattered/diffused by atmosphere like the higher frequencies may be.

IIRC, the ITU believes that 3 degree spacing is necessary in the Ka band broadcast.

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#153 OFFLINE   LameLefty

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Posted 13 August 2011 - 12:22 PM

Again, this is SPECIFICALLY ADDRESSED on p. 12 and Appendix A of the recently-filed Directv 97W Narrative document referenced by Sixto a couple of days ago, harsh and P Smith's vaguely-worded FUD notwithstanding. :rolleyes:

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#154 OFFLINE   Davenlr

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Posted 13 August 2011 - 12:29 PM

C-band isn't scattered/diffused by atmosphere like the higher frequencies may be.


All that would do is attenuate the signal, its not going to "move it" from 97 to 99 on the way down.

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#155 OFFLINE   harsh

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Posted 13 August 2011 - 12:33 PM

The higher frequency range of Ka, and the power levels of modern satellites, allow the smaller dishes we have on our roofs to work more like the 6 foot, multiple feed horn dishes used at earth stations for C-band. If you can make the LNBF only really see a 2 degree patch of sky, it doesn't really matter if there is another satellite 2 degrees away...the 97 LNBF won't see the 99 sats and viceversa.

How do you reconcile "work like" and Ka rain fade?

Does anyone use a 6' dish for C-band?

The question remains: can a Ka satellite at 97W deliver a CONUS signal to DIRECTV subscribers that will work with a OTARD qualifying dish?

Would DISH Network have been able to use the slot for similar purposes?

While there are many posts in this thread, few, if any have addressed this important question with definitive answers based on RF theory or practice. Because DIRECTV subscribers are back to singing the the virtues of quality over quantity again, this would seem to be an important distinction.

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#156 OFFLINE   veryoldschool

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Posted 13 August 2011 - 12:44 PM

How do you reconcile "work like" and Ka rain fade?

Does anyone use a 6' dish for C-band?

The question remains: can a Ka satellite at 97W deliver a CONUS signal to DIRECTV subscribers that will work with a OTARD qualifying dish?

Would DISH Network have been able to use the slot for similar purposes?

While there are many posts in this thread, few, if any have addressed this important question with definitive answers based on RF theory or practice. Because DIRECTV subscribers are back to singing the the virtues of quality over quantity again, this would seem to be an important distinction.

:nono: like you would even know any of these if they beat you over the head to get your attention. :nono:
"The only question" is really if our current reflectors will work for Ka from 97W, which may be the difference between the old AT-9 and the AU-9.
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#157 OFFLINE   P Smith

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Posted 13 August 2011 - 12:45 PM

More important, the projected DTV Ka sat @97W is offtopic and who knows if would be build:

Given the current absence of a construction contract for DIRECTV 97W, it is difficult to assess what satellites will actually be operating at the nominal 97° W.L. position at the time that the satellite is to be launched. As such, DIRECTV will certainly revisit this issue once a satellite construction contract is in place.

P. 17 of that initial doc.

Edited by P Smith, 13 August 2011 - 12:58 PM.


#158 OFFLINE   Davenlr

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Posted 13 August 2011 - 12:53 PM

Does anyone use a 6' dish for C-band?


Yes, I do. No issues with it at all, except low power from the satellite occasionally. I never have issues with other satellites next door. My actuator moves from one to the other, and the first disappears before the second appears.

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#159 OFFLINE   LameLefty

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Posted 13 August 2011 - 01:51 PM

More important, the projected DTV Ka sat @97W is offtopic and who knows if would be build:


No it is NOT off-topic. The topic is Directv satellite discussion. Parenthetically, it includes what we know about D14 because D14 was specifically mentioned in a recent investor presentation.

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#160 OFFLINE   P Smith

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Posted 13 August 2011 - 02:26 PM

Just keep the sidetrack for new 97W sat - what could be user friendly name of it ? D-15 ?

#161 OFFLINE   Tom Robertson

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Posted 13 August 2011 - 04:59 PM

Just keep the sidetrack for new 97W sat - what could be user friendly name of it ? D-15 ?


From the DIRECTV request document: "DIRECTV 97W". :)

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#162 OFFLINE   P Smith

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Posted 13 August 2011 - 06:02 PM

From the DIRECTV request document: "DIRECTV 97W". :)

Cheers,
Tom


Nice try, but I did read that document and saw the quotation - that's why I did ask in hope someone _knowledgeable_ would know an answer.
My guess (I'm not pretend to know) has been shown.

#163 OFFLINE   Tom Robertson

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Posted 13 August 2011 - 06:05 PM

With so many slots already active, it no longer makes sense to give them names until they are approved and construction is contracted. Anything else would get confusing.

Just look at D-13 that was requested, approved, and now has been abandoned.

So DIRECTV 97W or D97W is as good a name as any for now. :)

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#164 OFFLINE   P Smith

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Posted 13 August 2011 - 07:22 PM

So be it - "D97" :D.

#165 OFFLINE   LameLefty

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Posted 13 August 2011 - 07:37 PM

With so many slots already active, it no longer makes sense to give them names until they are approved and construction is contracted. Anything else would get confusing.


Aah, the voice of reason amidst the babble. Thank you, Tom! :)

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#166 OFFLINE   HoTat2

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Posted 13 August 2011 - 08:18 PM

2 degree spacing works on C band where the -3 db point on a standard 10' dish is much wider than a KU dish, and KA is even narrower (note the fine tuning adjusters needed for KA band?)

Turn your dish one degree, and see if you have any signal at all. Im sure the interference they are referring to, is interference from the ground station to neighbor satellites, not interference from the satellite to the ground stations.

With sufficiently large dishes at the uplink site, I have no worries they can avoid interference with a satellite 2 degrees away.


Alright, this sounds good for the most part;

But if the potential interference Tom spoke of refers to that of the uplink stations on adjacent satellites, then how can the use of "spot-beams" on the receiving satellite aid in preventing such interference to a neighboring satellite slot from its ground station?

#167 OFFLINE   veryoldschool

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Posted 13 August 2011 - 08:28 PM

Alright, this sounds good for the most part;

But if the potential interference Tom spoke of refers to that of the uplink stations on adjacent satellites, then how can the use of "spot-beams" on the receiving satellite aid in preventing such interference to a neighboring satellite slot from its ground station?

It has to be done from the ground.
You wouldn't use a "CONUS" beam pattern on a ground station as you'd "hit" every SAT up there. :lol:
Going back to the adjustable flashlight beam, you "merely" focus the beam narrow enough so as to not illuminate the SAT 2º [something like 800 miles] away.
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#168 OFFLINE   Tom Robertson

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Posted 13 August 2011 - 08:40 PM

Alright, this sounds good for the most part;

But if the potential interference Tom spoke of refers to that of the uplink stations on adjacent satellites, then how can the use of "spot-beams" on the receiving satellite aid in preventing such interference to a neighboring satellite slot from its ground station?


Sorry, didn't mean to confuse. The interference is not in the uplink direction. The monster dishes on the ground can focus a very tight beam that several uplink stations can hit separate dishes on a single satellite. As VOS describes, think of looking down at the earth and seeing 4 flashlights in the 4 corners of the US. Even if they are the same frequency, they are so far apart, it isn't a problem.

The interference is trying to receive the signals on the ground on a small dish from two satellites that are only 2° apart. It can be done--but we're talking about mass manufactured and mass installed dishes. So everthing needs to be slighly more precise for it to work everywhere. Hence the very fine tuning instructions and the problems of slightly warped dishes.

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#169 OFFLINE   James Long

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Posted 13 August 2011 - 11:28 PM

Sorry, didn't mean to confuse. The interference is not in the uplink direction. The monster dishes on the ground can focus a very tight beam that several uplink stations can hit separate dishes on a single satellite. As VOS describes, think of looking down at the earth and seeing 4 flashlights in the 4 corners of the US. Even if they are the same frequency, they are so far apart, it isn't a problem.

I read VOS's description (which specifically refers to a satellite 2º / 800 miles away) as the same uplink lighting up satellites at two different slots. If all works well a viewer at the satellite would only see ONE "flashlight" beam from one dish at the uplink. If they moved 800 miles to the next slot they would see a different beam from a different dish at the same uplink center.

What you are referring to is also possible ... designing a satellite with an uplink receive dish that would only see one area, such as Southern California, and another dish that would only see another area, such as Colorado. In that case a viewer at the satellite would see both "flashlight" beams (unless they were looking at the earth through the receive equipment - which would only see the appropriate beam).

The interference is trying to receive the signals on the ground on a small dish from two satellites that are only 2° apart. It can be done--but we're talking about mass manufactured and mass installed dishes. So everthing needs to be slighly more precise for it to work everywhere. Hence the very fine tuning instructions and the problems of slightly warped dishes.

There are also regional variances that need to be taken into account. Two degrees apart in space is not two degrees apart in an arc on the ground from every receive location. I believe it is possible to design a reflector that is 2º compliant in the Ka band.

#170 OFFLINE   LameLefty

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Posted 14 August 2011 - 08:04 AM

I'm sure the highly-educated and well-trained RF engineers at Directv and their counterparts at Boeing and SS/L who design the satellites will appreciate our collective approval of their abilities. :rolleyes:

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#171 OFFLINE   Alan Gordon

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Posted 16 August 2011 - 11:18 AM

I would say so as well, were it not for Tom's earlier statement about the Ka-band payloads at 101 actually being spot-beamed to eliminate potential interference with 99 and 103.


I would imagine that DirecTV is a forward enough thinking company to have done some testing at 101°...

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#172 OFFLINE   Sixto

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Posted 16 August 2011 - 06:34 PM

While there's only been one public Space Systems / Loral (SS/L) press release, the FCC docs clearly refers to two birds, with both being updated within the past few weeks.

RB-1 (at 99°):

Modification: http://licensing.fcc...ment_key=907941

Schedule-S: http://licensing.fcc...ment_key=908556

RB-2 (at 103°):

Modification: http://licensing.fcc...ment_key=907995

Schedule-S: http://licensing.fcc...ment_key=908568


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#173 OFFLINE   HoTat2

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Posted 16 August 2011 - 08:55 PM

Still no filings on the Ka-band payload clearly mentioned in the SS/L press release for DIRECTV 14/RB-1?

Very strange ...

#174 OFFLINE   Sixto

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Posted 16 August 2011 - 09:12 PM

Still no filings on the Ka-band payload clearly mentioned in the SS/L press release for DIRECTV 14/RB-1?

Very strange ...

I've always assumed that the press release was referring to either RB-1 or RB-2, and for whatever reason they decided to only mention one. It seems clear in the filings that SS/L is building two satellites.
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#175 OFFLINE   HoTat2

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Posted 17 August 2011 - 09:12 AM

I've always assumed that the press release was referring to either RB-1 or RB-2, and for whatever reason they decided to only mention one. It seems clear in the filings that SS/L is building two satellites.


Yea;

But I'm just still trying to ascertain as to whether or not RB-1 designated for 99W (don't know about RB-2) will contain a Ka-band payload as well or not. Had thought the mention of Ka in the original press release implied another D12 type set of Ka-hi transponders for 99W.

A possible "99ca" perhaps?




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