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Transponder Maps: Domestic & LatinAm ~ Data Refresh 2/25/2015


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688 replies to this topic

#676 OFFLINE   slice1900

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Posted Yesterday, 02:19 PM

The Spaceways can use transponders 1/2 and 5/6 at identical center frequencies to the standard Ka plan transponders 1/2 and 7/8 . They may in fact already do so - aside from the information on Lyngsat which we know is not always correct (and in any case is wildly out of date) I don't think we know for sure what center frequency SW1 and SW2 use today.

 

Your objection would only matter for Spaceway transponders 3/4, and then only for the signal strength screen; for tuning a channel it wouldn't matter. To get around the problem for the signal strength screen, who says D14 and SW2 would have to overlap their transponders on 99s? Use 9-10 for the slightly offset frequency SW2 3/4 would be forced to use. Or heck, if SW2 uses different center frequencies for all of them, display D14 on 99s 1-8, SW2 on 9-14 and D11 on 15-24! :righton:


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#677 OFFLINE   tomspeer46

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Posted Yesterday, 08:13 PM

 

Your objection would only matter for Spaceway transponders 3/4, and then only for the signal strength screen; for tuning a channel it wouldn't matter. To get around the problem for the signal strength screen, who says D14 and SW2 would have to overlap their transponders on 99s? Use 9-10 for the slightly offset frequency SW2 3/4 would be forced to use. Or heck, if SW2 uses different center frequencies for all of them, display D14 on 99s 1-8, SW2 on 9-14 and D11 on 15-24! :righton:

 

It is not just the center frequency.  It is the entire width of each transponder.  SW2 and D14 cannot overlap any part of their respective channels without causing interference. 


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#678 OFFLINE   HoTat2

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Posted Yesterday, 09:20 PM

For reference from the Schedule S for D14 xpndrs 1-8 center frequencies.

Pair 1/2 - 19730 MHz
Pair 3/4 - 19770 MHz
Pair 5/6 - 19810 MHz
Pair 7/8 - 19850 MHz

For SW2 operating in non-processor ("bent pipe") mode according to it's Schedule S.

Pair 1/2 - 19731.5 MHz
Pair 3/4 - 19794 MHz
Pair 5/6 - 19856.5 MHz

So while I would agree that pairs 1/2 and 7/8 of D14 may be sufficently close to SW2's pairs 1/2 and 5/6 so as to be feasible for use together, I can't imagine DIRECTV wanting to sacrifice the use of two CONUS xpndrs 9/10 from D14 just to keep SW2 in use with those 4 spotbeam xpndr frequencies at it's disposal.

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Edited by HoTat2, Today, 02:32 AM.

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#679 OFFLINE   tomspeer46

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Posted Yesterday, 10:23 PM

HoTat2- You make a good point.  The fact that SW2 transponder 5&6 encroaches on the passband of D14 9/10 would make it undesirable in the long run.  It will be interesting to see how they perform the migration from the spot beams of SW2.  It is unlikely that they will do a flash cut of all SW2 spot beams to D14, since they occupy the same spectrum, and can't be up simultaneously.


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#680 OFFLINE   slice1900

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Posted Today, 01:05 AM

It is not just the center frequency.  It is the entire width of each transponder.  SW2 and D14 cannot overlap any part of their respective channels without causing interference. 

 

The transponder width is merely the width of the filters in the satellite. It receives a signal uplinked from the ground, which is amplified and filtered before it is downlinked to the dishes on our roof. If the signal that is uplinked only partially fills the 62.5 MHz of available width, with the unused portion filtered to be much weaker (they could easily get it 100 db down a couple MHz to each side of the main 30 MHz wide signal) there shouldn't be any interference to speak of. Unless the TWTA is going to amplify those unused portions that are 100 db down much more so than the main signal which I don't believe to be the case.

 

The SNR of DBS Ka transponders is only about 15 db or so best case, so as long as the unused portions are more than 15 db down, the interference is "lost in the noise" :)


Edited by slice1900, Today, 01:07 AM.

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#681 OFFLINE   inkahauts

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Posted Today, 03:07 AM

I wonder if the sw will be retasked to a different roll of some sort. To bad they can't move one to 110...

#682 OFFLINE   P Smith

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Posted Today, 06:19 AM

The transponder width is merely the width of the filters in the satellite. It receives a signal uplinked from the ground, which is amplified and filtered before it is downlinked to the dishes on our roof. If the signal that is uplinked only partially fills the 62.5 MHz of available width, with the unused portion filtered to be much weaker (they could easily get it 100 db down a couple MHz to each side of the main 30 MHz wide signal) there shouldn't be any interference to speak of. Unless the TWTA is going to amplify those unused portions that are 100 db down much more so than the main signal which I don't believe to be the case.

 

The SNR of DBS Ka transponders is only about 15 db or so best case, so as long as the unused portions are more than 15 db down, the interference is "lost in the noise" :)

I did the measures of SW's tpns and posted it here, you should remember as I did answer to [your?] same question before ;)


Edited by P Smith, Today, 06:19 AM.


#683 OFFLINE   tomspeer46

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Posted Today, 09:32 AM

I did the measures of SW's tpns and posted it here, you should remember as I did answer to [your?] same question before ;)

I haven't found your actual measurements. I assume from some other postings that you used a spectrum analyzer and found that the SW2 spot beams were modulated to a 36 Mhz bandwidth around the center frequency, just as specified in Schedule S for the D14 transponders (different frequencies).  That is what I was assuming when I said that SW2 tpn 5/6 would encroach on the passband of D14 TPN 9/10.  That would be true unless DirecTV can somehow shift the center frequency of the SW2 transponder down while still staying within its licensed (62.5 Mhz?)  bandwidth.  That may not be possibly either legally or technically.

If the actual modulation is only 30 Mhz as slice1900 indicates, then my analysis could be wrong.

I agree that it looks like D14 will eventually replace the spot beams from SW2, because it makes more efficient use of the licensed spectrum from that location, by packing more 36Mhz transponders into the available spectrum.  It remains to be seen how and when that will occur.  There may be financial reasons to do that also.


Edited by tomspeer46, Today, 09:37 AM.

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#684 OFFLINE   HoTat2

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Posted Today, 09:50 AM

I haven't found your actual measurements. I assume from some other postings that you used a spectrum analyzer and found that the SW2 spot beams were modulated to a 36 Mhz bandwidth around the center frequency, just as specified in Schedule S for the D14 transponders (different frequencies). That is what I was assuming when I said that SW2 tpn 5/6 would encroach on the passband of D14 TPN 9/10. That would be true unless DirecTV can somehow shift the center frequency of the SW2 transponder down while still staying within its licensed (62.5 Mhz?) bandwidth. That may not be possibly either legally or technically.
If the actual modulation is only 30 Mhz as slice1900 indicates, then my analysis could be wrong.
I agree that it looks like D14 will eventually replace the spot beams from SW2, because it makes more efficient use of the licensed spectrum from that location, by packing more 36Mhz transponders into the available spectrum. It remains to be seen how and when that will occur. There may be financial reasons to do that also.

Correct;

And this why SW1 at 103W was reduced from 6 to 4 active xpndrs (pairs 1/2 and 3/4) some time ago when DIRECTV lit up service on D12's CONUS xpndrs 9 and 10.

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#685 OFFLINE   doctor j

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Posted Today, 10:01 AM

Gary, any chance you can do a quick check to see if 171 *CINEHD on Net 15 TID 132 changed to something else? It was taken down yesterday morning so it's possible you did the grab before they changed it to be a new HD channel in test.

No change on 3/1 update

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#686 OFFLINE   slice1900

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Posted Today, 01:57 PM

If the actual modulation is only 30 Mhz as slice1900 indicates, then my analysis could be wrong.
 

I agree that it looks like D14 will eventually replace the spot beams from SW2, because it makes more efficient use of the licensed spectrum from that location, by packing more 36Mhz transponders into the available spectrum.  It remains to be seen how and when that will occur.  There may be financial reasons to do that also.

 

The signals are 30 Ms/s (30 MHz) same as the other spots and CONUS Ka. They couldn't make full use of the width of the Spaceway transponders because it wouldn't be compatible with SWM (and most tuner SoCs can't go wider than 45 Ms/s anyway)

 

I agree that SW2 may well go elsewhere, but if it does the question is what Directv will do to fill in the markets it is covering that D14 does not have spot beams for. Are there unused spot beams on D11 or D12 to cover those markets? Will D14 free up enough spotbeams on SW1 that SW1 can pick up all of them? What about the remaining DMAs that aren't covered? D14 adds only one of those, Ottumwa/Kirksville.

 

Maybe SW2 moves to 103 to "help" SW1 with those remaining markets. Or if D11/D12/D14/SW1 alone can cover everything, or SW1 already covers everywhere it can on all spots so SW2 would be no help, SW2 might be dedicated to Puerto Rico.


Edited by slice1900, Today, 01:57 PM.

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#687 OFFLINE   P Smith

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Posted Today, 02:50 PM

The signals are 30 Ms/s (30 MHz) same as the other spots and CONUS Ka...

if you'll count roll-off 0.2 then it will come to 32..36 MHz, not 30 MHz

#688 OFFLINE   tomspeer46

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Posted Today, 03:27 PM

While I have no direct knowledge of the actual transponder signals, P Smith's answer makes more sense.  I've had over 35 years in dealing with radios and data communications, I've never seen a modulation scheme that created a spectrum with absolutely vertical sidewalls on a spectrum analyzer.  The data rate does not determine the exact bandwidth of the modulated signal.  There is a reason the transponders on D14 use a 36 Mhz bandpass and are spaced 40 Mhz apart to avoid adjacent channel interference.


Edited by tomspeer46, Today, 03:42 PM.

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#689 OFFLINE   HoTat2

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Posted Today, 04:22 PM

if you'll count roll-off 0.2 then it will come to 32..36 MHz, not 30 MHz

Lost me there P. Smith;

Bandwidth = (1 + Roll-off factor) x Symbol Rate

So for a 0.2 roll-off and a 30 ms/s SR, isnt that a 36 MHz bandwidth transmission?

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