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DIRECTV Satellite Discussion D-14 @99W


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#126 OFFLINE   P Smith

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Posted 12 August 2011 - 10:40 AM

Yup, and there's some general DIRECTV Ka info in this thread: http://www.dbstalk.c...ead.php?t=82295


Doesn't count - those freq should be allocated in different range, therefor is not receivable by subscriber's disnes/LNBFs.

#127 OFFLINE   LameLefty

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Posted 12 August 2011 - 11:38 AM

Doesn't count - those freq should be allocated in different range, therefor is not receivable by subscriber's disnes/LNBFs.


Stop being pedantic. Doesn't necessarily matter - RF is wavelike and interference can occur even without the customer's LNB being able to receive it.

Besides, and more to the point, interference is already addressed by Directv in its documentation (I provided the reference above). If you'd take the time to read it you'd realize it isn't an issue.

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#128 OFFLINE   Go Beavs

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Posted 12 August 2011 - 02:18 PM

Doesn't count - those freq should be allocated in different range, therefor is not receivable by subscriber's disnes/LNBFs.


Sorry, I'm no RF expert. I just figured Ka is Ka. Assumptions can bite you (me) sometimes. :)

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#129 OFFLINE   LameLefty

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Posted 12 August 2011 - 02:18 PM

Sorry, I'm no RF expert. I just figured Ka is Ka. Assumptions can bite you (me) sometimes. :)


His answer is irrelevant - see my subsequent post.

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#130 OFFLINE   P Smith

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Posted 12 August 2011 - 03:43 PM

Sorry, I'm no RF expert. I just figured Ka is Ka. Assumptions can bite you (me) sometimes. :)

NP, perhaps we are talking about SPECIAL allocation for 101W Ka's use. Not for us, mere mortal. :)

#131 OFFLINE   Tom Robertson

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Posted 12 August 2011 - 04:20 PM

Doesn't count - those freq should be allocated in different range, therefor is not receivable by subscriber's disnes/LNBFs.


The frequency range for the slot is the same as for 99° and 103°. That the block of frequency is broken up differently at 101° doesn't matter. The wavelengths "could" interfere.

What DIRECTV does is spotbeam the backhauls at 101° to minimize the likelihood of interference.

So what would DIRECTV do at 97°? Since they've specified transponders, I'm guessing they have enough experience with Ka they know they can make 2° spacing work.

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#132 OFFLINE   P Smith

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Posted 12 August 2011 - 04:41 PM

The frequency range for the slot is the same as for 99° and 103°. That the block of frequency is broken up differently at 101° doesn't matter. The wavelengths "could" interfere.

What DIRECTV does is spotbeam the backhauls at 101° to minimize the likelihood of interference.

So what would DIRECTV do at 97°? Since they've specified transponders, I'm guessing they have enough experience with Ka they know they can make 2° spacing work.

Cheers,
Tom

Perhaps Ka Spot Beams only.

#133 OFFLINE   P Smith

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Posted 12 August 2011 - 04:43 PM

May be it's time to make new dedicated thread for Ka at 97W?

And clean the thread from off-topic posts ?

#134 OFFLINE   veryoldschool

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Posted 12 August 2011 - 04:45 PM

The frequency range for the slot is the same as for 99° and 103°. That the block of frequency is broken up differently at 101° doesn't matter. The wavelengths "could" interfere.

What DIRECTV does is spotbeam the backhauls at 101° to minimize the likelihood of interference.

So what would DIRECTV do at 97°? Since they've specified transponders, I'm guessing they have enough experience with Ka they know they can make 2° spacing work.

Cheers,
Tom

From the FCC website here: http://transition.fc...a/faq.html#FAQ6

The Commission's two-degree orbital spacing policy, which was established in 1983, maximizes the number of satellites in orbit by ensuring that Fixed Satellite Service (FSS) satellites in geostationary-satellite orbit (GSO) can operate without causing harmful interference to other GSO FSS satellites located as close as two degrees away. Prior to the Commission's adoption of the two-degree spacing policy, GSO FSS satellites were usually spaced three or four degrees apart. By adopting rules that enabled satellite operators to place their space stations two degrees apart, the Commission was able to accommodate more GSO FSS satellites. The two-degree orbital spacing policy is important for earth station applicants because the Commission, among other things, adopted a number of rules that would ensure that earth stations communicating with satellites at two-degree orbital separations would not cause unacceptable interference to adjacent satellite systems using the same frequency bands. These rules include earth station antenna diameter and performance requirements, and power restrictions embodied in 47 C.F.R. §§ 25.134, 25.209, 25.211, and 25.212. See Routine Licensing of Earth Stations in the 6 GHz and 14 GHz Bands Using Antennas Less than 9 Meters and 5 Meters in Diameter, respectively, for Both Full Transponder and Narrowband Transmissions, Declaratory Order, 2 FCC Rcd 2149 (Com. Car. Bur., 1987), cited in 47 C.F.R. § 25.134. For more information on the Commission’s two-degree orbital spacing policy, see Licensing of Space Stations in the Domestic Fixed-Satellite Service and Related Revisions of Part 25 of the Rules and Regulations, Report and Order, CC Docket No. 81-704, FCC 83-184, 54 Rad. Reg. 2d 577 (rel. Aug. 16, 1983); summary printed in Licensing Space Stations in the Domestic Fixed-Satellite Service, 48 F.R. 40233 (Sept. 6, 1983).


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#135 ONLINE   David Ortiz

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Posted 12 August 2011 - 04:50 PM

From 2007:

C, Ku, Ka
Unlike C band transponders, Ku and Ka do not have standardized transponder frequencies (although, DBS usage of Ku has been standardized by the FCC and ITU). Outside of the dbs satellites, to use a Ku transponder, an engineer needs to verify (and double check) the specific frequencies for that particular satellite.

Ka is even more flexible. D8 and D9s were always surprising to me in that they only had a very few Ka transponders. What I did not realize is that each transponder’s signal is 250mhz wide. While not very useful for dbs purposes, they are quite useful for backhauling OTA signals around the country ultimately for uplink to the spotbeams from the satellites at 99° or 103°.

Ka satellite locations can operate with 2 degrees of separation, narrower than the 4 degree necessary for Ku.

Typical Ka dbs licenses allow two 500 mhz ranges of downlinking: 19.7-20.2 GHz (A-band) and 18.3-18.8GHz (B-band) as well as three more of uplinking. Ku licenses allow one 500 mhz range each.

Directv standard Ku transponders, numbered 1-32, are 29mhz wide with 24mhz usable. For D10 and D11, Ka transponders are numbered 1-24, and are 40mhz wide with 36mhz usable. S1 and S2 can be operated as eight transponders 62.5mhz wide.

Ku transponders alternate polarity and are offset in frequency much like two courses of bricks. Ka transponders also alternate polarity, but operate on the exact same frequency for adjacent even and odd transponders.

Because of the smaller guard frequenies between transponder channels and the overlapping structure of Ka vs. the offset used by Ku, Ka gives about 10% more usable bandwidth.
Ku usable bandwidth from 500mhz available is 384mhz.
Ka usable bandwidth from 500mhz available is 432mhz.



#136 OFFLINE   P Smith

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Posted 12 August 2011 - 07:30 PM

You can read and re post here for long period of time ... it will didn't change your LNBF to 4x or 6x; it's already complicated enough to give headache during manufacturing and installs.

#137 ONLINE   David Ortiz

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Posted 12 August 2011 - 07:37 PM

You can read and re post here for long period of time ... it will didn't change your LNBF to 4x or 6x; it's already complicated enough to give headache during manufacturing and installs.


We're a long way from swapping out hardware, of course, but it is interesting that the 2 degree spacing was talked about long ago.

#138 OFFLINE   P Smith

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Posted 12 August 2011 - 07:55 PM

Sure, yes. My point is our dishes and LNBF still use 4 degree spacing.

BTW, I will remind you another factor - 12' dish has 1.4 degree diagram and can separate two sats at 2 degree spacing, yet 1m [39"] or worst 24".

#139 OFFLINE   Tom Robertson

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Posted 12 August 2011 - 08:00 PM

Sure, yes. My point is our dishes and LNBF still use 4 degree spacing.

BTW, I will remind you another factor - 12' dish has 1.4 degree diagram and can separate two sats at 2 degree spacing, yet 1m [39"] or worst 24".


Well... The dish and LNBF only use 4° spacing for an individual frequency grouping, they use 2° spacing between LNBFs.

Another theory is that DIRECTV didn't want to manufacture an LNBF head that tried to fit both Ka and Ku at the 101° slot. Sure it can be done, but at what manufacturing precision and cost?

Perhaps 97° is a no brainer since there isn't anything else there.

Cheers,
Tom

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#140 OFFLINE   Davenlr

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Posted 12 August 2011 - 08:06 PM

Does DirecTv own the KA slow at 101?

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#141 OFFLINE   Tom Robertson

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Posted 12 August 2011 - 08:07 PM

Does DirecTv own the KA slow at 101?


Yes. DIRECTV uses it for backhauling.

Cheers,
Tom

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#142 OFFLINE   Davenlr

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Posted 12 August 2011 - 08:09 PM

Yes. DIRECTV uses it for backhauling.

Cheers,
Tom


Ok, thanks Tom. Knew about the backhauls, but thought it was a separate license for the trip back on KA.

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#143 OFFLINE   harsh

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Posted 13 August 2011 - 08:40 AM

From the FCC website here: http://transition.fc...a/faq.html#FAQ6

The portion of the article you quote speaks to FSS that is both very low power and below DBS band in frequency.

The references to dishes smaller than 9m and 5m suggests they're not talking about multi-focal offset "pizza dishes".

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#144 OFFLINE   veryoldschool

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Posted 13 August 2011 - 09:00 AM

The portion of the article you quote speaks to FSS that is both very low power and below DBS band in frequency.

The references to dishes smaller than 9m and 5m suggests they're not talking about multi-focal offset "pizza dishes".

Since it dates back to 1983, I'd say it has everything to do with the spacing of the SATs and the uplinking to them, leaving the downlink "issues" to the providers to sort out, with the parabolic shape of the reflector.
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#145 OFFLINE   harsh

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Posted 13 August 2011 - 09:22 AM

Since it dates back to 1983, I'd say it has everything to do with the spacing of the SATs and the uplinking to them, leaving the downlink "issues" to the providers to sort out, with the parabolic shape of the reflector.

I thought the discussion was whether or not any DBS provider could use 97W for additional Ka broadcast capacity as opposed to uplinks or backhauls.

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#146 OFFLINE   veryoldschool

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Posted 13 August 2011 - 09:29 AM

I thought the discussion was whether or not any DBS provider could use 97W for additional Ka broadcast capacity as opposed to uplinks or backhauls.

I'd say enough posts here have shown the 2º spacing has proven to work, so 97W wouldn't be an issue, "other than" if our [not yours] current dish would need to be reshaped.
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#147 OFFLINE   Diana C

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Posted 13 August 2011 - 10:37 AM

Can Ka slots be spaced only 2 degrees apart?


How ? What reasons you have in mind what would ALLOW positioning Ka sats close as C-band sats ? Not following Ku sats rules ?


Directv is already using Ka band 2º apart - there are Ka backhauls at 101º already.

See page 12 and Appendix A of the document Sixto provided for discussion of interference analysis.


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.

#148 ONLINE   HoTat2

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Posted 13 August 2011 - 11:08 AM

I'd say enough posts here have shown the 2º spacing has proven to work, so 97W wouldn't be an issue, "other than" if our [not yours] current dish would need to be reshaped.


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.

If true, then we really have no working examples today of two Ka-band CONUS beam birds with 2 degree separation. Not at all saying it won't work of course, but just pointing that it wouldn't be correct to say DIRECTV is already using 2 degree adjacent Ka-band slots in the way DIRECTV-97W and the satellites at 99W are intended for.

This is all assuming Tom is correct about the Ka-band back-hauls at 101 being spot-beamed of course. :)

#149 OFFLINE   veryoldschool

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Posted 13 August 2011 - 11:19 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.

If true, then we really have no working examples today of two Ka-band CONUS beam birds with 2 degree separation. Not at all saying it won't work of course, but just pointing that it wouldn't be correct to say DIRECTV is already using 2 degree adjacent Ka-band slots in the way DIRECTV-97W and the satellites at 99W are intended for.

This is all assuming Tom is correct about the Ka-band back-hauls at 101 being spot-beamed of course. :)

What all of this really comes down to is the focus of both the ground uplink dish and the SAT receiving dish. Being the old fart that I am, I remember when the FCC ruling came out after testing and an engineer's discussion of this ruling and its "impact".
This really isn't much different that filtering of a tuner to keep out adjacent channels, but instead is the focusing of the dish signal, on the uplink path.
Think of all the CONUS & spot beams that our dishes "filter out" so they can receive the SAT that we want.

For those having a hard time with this, think of an adjustable flashlight that you can focus the beam with. The dish on the uplink works the same way.

Edited by veryoldschool, 13 August 2011 - 11:46 AM.

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#150 OFFLINE   Davenlr

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Posted 13 August 2011 - 11:21 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.

If true, then we really have no working examples today of two Ka-band CONUS beam birds with 2 degree separation.


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.

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