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Thread: Transponder Maps ~ Data 10/16/2019

  1. #1501
    Super Moderator Tom Speer's Avatar
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    I just thought there might be some near field effects of two adjacent dishes transmitting on the same frequency. I understand that a dish that big can target a single satellite, as long as they are far enough apart, wandering about their orbital "boxes", so that there is no interference from the adjacent uplink beam.
    Tom Speer, N2HF, the curious otter. Part of the DataDigesters team.

  2. #1502
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    Quote Originally Posted by Tom Speer View Post
    I just thought there might be some near field effects of two adjacent dishes transmitting on the same frequency. I understand that a dish that big can target a single satellite, as long as they are far enough apart, wandering about their orbital "boxes", so that there is no interference from the adjacent uplink beam.
    Oh there very may well be ....

    As I'm certain there are considerations for an appropriate physical spacing of the ground stations. Especially when transmitting on the same uplink frequencies. I just couldn't see how it could cause co-channel interference at the satellite receiver's input.

    In fact this was one of the questions I wanted to ask "inclined orbit" about, but (and much to my dissappointment) he really didn't know since he wasn't familiar with the older Ku band DBS unplink dishes and operations at the LABC and CRBC.

    But only the Ka band uplink facilities for 99 and 103W, which never use (or need to) the same CONUS and spotbeam uplink frequencies from the same uplink site.

    Since they use more than two (4 to 6) for spotbeam tp. capacity of course ...

  3. #1503
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    Quote Originally Posted by HoTat2 View Post
    What do you mean?

    Why wouldn't any subs. in PR and the USVI (comparatively few though they may be) be able to see 101W any longer?
    Ah I was thinking Mexico for some reason, where people are losing ability to see 101 tpns due to the tighter CONUS pattern for T15 (and presumably T16) than the older satellites.

    Yes, PR customers should see additional CONUS transponders if the evens are now coming from T15/T16. They probably took a partial hit from the recent hurricane and might have more important considerations. Even if they didn't get the brunt of the wind if you get a foot of rain it can cause a lot of problems...

  4. #1504
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    Quote Originally Posted by Tom Speer View Post
    I just thought there might be some near field effects of two adjacent dishes transmitting on the same frequency. I understand that a dish that big can target a single satellite, as long as they are far enough apart, wandering about their orbital "boxes", so that there is no interference from the adjacent uplink beam.
    I doubt that's a big problem. When spacing antennas you are supposed to maintain horizontal separation of 1/2 the wavelength (and avoid exact multiples of the wavelength up to 3-4x or so) That's a consideration with VHF or ham antennas, but for Ku with such a tiny wavelength and such giant dishes I doubt it matters. If you look at the overhead photos they seem to have them fairly close together - the limit of HOW close is probably dictated by leaving room for a crane to get in for installation/decomissioning!

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    And another question I have is that since the big uplink dishes are able to resolve to within .1° or less at the Clarke belt. Are the dishes then not really stationary, but actually have to track the satellite throughout its daily figure-8 drift (or "analemma") by moving slightly in elevation and azimuth during the day as necessary to keep their narrow transmit beams centered on the satellite at all times?

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    In related news, the 30 day STA to de-orbit D4S begins today.

    Also, moving those D9S transponders to D15 would explain why some of these Puerto Rican test SD channels appeared on even transponders back in June:
    Quote Originally Posted by kyl416 View Post
    Puerto Rico now has test feeds for the following SD channels from the 101 slot:
    223 Viceland*
    264 Fuse
    265 BET*
    270 GSN
    354 CTN
    524 Sundance
    526 IFC*

    * There's probably going to be another 101 reshuffle in the near future because several of these are currently on D9S transponders

  7. #1507
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    Quote Originally Posted by HoTat2 View Post
    And another question I have is that since the big uplink dishes are able to resolve to within .1° or less at the Clarke belt. Are the dishes then not really stationary, but actually have to track the satellite throughout its daily figure-8 drift (or "analemma") by moving slightly in elevation and azimuth during the day as necessary to keep their narrow transmit beams centered on the satellite at all times?
    Isn't the 'box' much smaller than .1 degree? I would imagine they'd want to size the big dishes so they are large enough to hit only one satellite, but small enough that they can aim them in the center of the 'box' and not have to move the dish. Having tracking motors on those dishes would make them much more expensive and more prone to failure.

  8. #1508
    Super Moderator Doctor j's Avatar
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    D4s TLE from just before MN last night shows no movement yet.

    101.1567W position
    period 23 Hr 56 mins 5 seconds
    35,781 x 35,792 Km orbit

    Doctor j

  9. #1509
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    Quote Originally Posted by slice1900 View Post
    Isn't the 'box' much smaller than .1 degree? I would imagine they'd want to size the big dishes so they are large enough to hit only one satellite, but small enough that they can aim them in the center of the 'box' and not have to move the dish. Having tracking motors on those dishes would make them much more expensive and more prone to failure.
    Perhaps that's it ...

    Since the FCC max. tolerance for GSO is +/- .05° N<-->S and E<-->W. Perhaps such precise satellite dish AZ/EL tracking from a ground station is unnecessary, expensive, and overly burdensome on the dish positioning motors for such massive dishes.

    So the dish remains fixed on just the center of the satellite's orbital "box" then.

  10. #1510
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    Quote Originally Posted by kyl416 View Post
    In related news, the 30 day STA to de-orbit D4S begins today.

    Also, moving those D9S transponders to D15 would explain why some of these Puerto Rican test SD channels appeared on even transponders back in June:
    Oh!

    Wasn't even aware of those ...

    Always in the habit of only looking at the top few stations in test at the top of the Excel sheet under the "Hybrid" tab.

    So I guess this is the next best evidence for the even numbered CONUS tps. on 101W are active on T15 or 16, short of having a sub. reporting in from PR or the USVI.

    For why would DIRECTV label those SD channels in test as for PR and place them on T9S which can't reach them....

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