Spot Beam

[Skip Towne]

How much area does a spot beam cover?

[BobJ2004]

Any have have current spot beam maps for the 101 and the new 7s sats?

What to make sure the locals are in the right place in case I "move".

[Mark Holtz]

http://ekb.dbstalk.com/297

There is another chart someplace, but I can't locate it at the moment.

[Mike123abc]

Spot beams can be pretty much any size, depends on what they want to accomplish. I think the practical limit for Ku is about 500 miles diameter minimum (antenna size limits because of launch vehicle size... bigger antenna in space needed for a smaller tighter focus). DIRECTV seems to be using various sized spots, E* seems to be using fixed size. Note that curve of the earth makes them ovals.

[reddice]

What is a spot beam, always wondered.

[ddobson]

What is a spot beam, always wondered.

I'm not an expert but here's my understanding. Utilizing spot beams to limit coverage to a relatively small area, as opposed to covering the entire country means they can use the same transponder frequencies multiple times.

For example, say they were using transponders (channels) 1 and 3 for Chicago locals. If that beam covered the entire country, 1 and 3 could be used for nothing else. Utilizing spot beams the signals can be shot from different antennas on the satellite to cover areas 500 miles or so in diamater. So you can draw a circle around, New York, Chicago, Denver, L.A., Seattle, Orlando etc., and use the same transponder frequencies for all of those cities from the same satellite in the same location (101 or 119).

It gives them the ability to put hundreds of channels up there that they otherwise wouldn't have space for. If you look at the map links listed above, they can use the same transponders in several cities. There may be a buffer area that I'm not aware of for safety but they can at least use the same transponders several times over.

Otherwise if you think about it they're kind of limited. I beleive there are 32 transponders per satellite and DirecTV has 3 locations in space for satellites sot they're stuck at 96 channels. Now compression would obviously multiply that several times however when you look at the fact there are over 1600 local channels in the U.S., they can't possibly think about carrying even 1/3 of them without spot beam technology.

DirecTV has another spot beam on order I beleive due for mid 2005. I've got a feeling after the flack and delays on this one they will push much harder to have that one launched on time. I have no idea what the plans are for that satellite. It must either be a backup or replacement for 4S since the press release said it was designed to work at 101 or 119 and both of those will already be spot beams. Or perhaps they can use the satellite to provide even more spot beams from the same location, although I would think the uplinks would be an issue if the satellites are at the same location.

Time will tell on that and we'll have to wait and see.

If anyone else has any comments or wishes to correct me please please feel free. Just thought I'd jump in with my understanding, right or wrong I guess :)

[Skip Towne]

Thanks, ddobson. That is the best explanation I've seen. Much appreciated.

[AntAltMike]

Utilizing spot beams to limit coverage to a relatively small area, as opposed to covering the entire country means they can use the same transponder frequencies multiple times...

It gives them the ability to put hundreds of channels up there that they otherwise wouldn't have space for...

Otherwise if you think about it they're kind of limited. I believe there are 32 transponders per satellite and DirecTV has 3 locations in space for satellites sot they're stuck at 96 channels. Now compression would obviously multiply that several times however when you look at the fact there are over 1600 local channels in the US, they can't possibly think about carrying even 1/3 of them without spot beam technology.

DirecTV has another spot beam on order I believe due for mid 2005... I have no idea what the plans are for that satellite. It must either be a backup or replacement for 4S since the press release said it was designed to work at 101 or 119 and both of those will already be spot beams. Or perhaps they can use the satellite to provide even more spot beams from the same location, although I would think the uplinks would be an issue if the satellites are at the same location.


DirecTV had transponder allocations in three slots, but it only owns 3 transponders in the 110 degree slot, and eleven transponders in the 19 degree slot.

DirecTV 4S can receive uplinked signals from two sites, so it can make available for redistribution up to 64 unique downlink beams. Presently, 4S is emitting 26 CONUS (continental United States) beams, and 44 transponder-width spot beams that carry 38 unique transponders of programming. If DirecTV 7S can receive uplinked signal from three sites, then it could distribute 33 transponders of programming from the 19 degree slot. If six of the eleven transponder allocations in that slot are used for spot beaming, then the spot beams from that slot could carry up to 28 unique transponder-width beams of programming. Operating a spot beam satellite from the 110 degree slot, with only three transponders of uplink and downlink frequency available, probably does not work out economically.

The third spot beam satellite will be a very expensive back-up. I suspect that it will be put into service as soon as it is made operational to provide locals to the markets that remain unserved by 4S and 7S, but I also would expect DirecTV to have a very specific "liquidated damages" clause in the subscription contracts for customers in those markets, telling them exactly what they would be entitled to if the third spot beam satellite ever had to be reassigned to replace either of the more productive ones.

[jdspencer]

This map may be of help to see what spot beams are used where.

http://www.scottandmichelle.net/scott/dtv.html

[goodcableguy]

Here is an excellent link to spotbeam maps.

http://ekb.dbstalk.com/297