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TexasRebel

join:2011-05-29
Edgewood, TX

Does dish reflector shape determine signal strength?

Just curious why HN's satellite internet dish is oval and if it's better than the WB shaped dish, which is more circular in shape??

I know the whole idea of oval shaped dishes with satellite tv and receiving signals from multiple satellites. Just was wondering if the shape changes the beam pattern that's transmitted.

The beam pattern off circular reflectors looks like a cylinder. I was wondering if oval reflectors put out an oval shaped beam??

Just curious..

The gateway antennas use something like a 30ft. reflector, which is pretty circular in their shape and I'm guessing they use around 50-100 watts for the transmitting to cut through heavy cloud cover and thermal changes in the atmosphere..


grohgreg
Dunno. Ask The Chief

join:2001-07-05
Dawson Springs, KY
I don't know how much of that post was musing, and how much contained questions for which you actually expect answers. From a US-provider standpoint, Hughes is a much more diverse outfit than is ViaSat (and the former WildBlue). Specifically, Hughes provides both Ku- and Ka-band service. As such, they have a plethora of dishes on the ground, as compared to those fielded by Wildblue/Exede/ViaSat.

Perhaps you could be more specific as to what you're looking for in a response.

//greg//
--
HN7000S - 98cm Prodelin/2w "pure" Osiris - ProPlus - G16/1001H - NOC:GTN - NAT 67.142.115.130 - Gateway 66.82.25.10 - DNS 66.82.4.12 and 66.82.4.8 - Firefox 15/MSIE9 - AV/Firewalled by NIS2012


dbirdman
Premium,MVM
join:2003-07-07
usa
kudos:5
reply to TexasRebel
Only the Hughes Ku-Band antenna is an oval, and they built a couple of different ovals, with later ones being "less oval."

The narrowness of the beam is a function of size - bigger is narrower. An antenna that is oval produces a narrower beam on the wide dimension than on the narrow dimension (in other words, they are opposite in effect). In theory, a dish that is elongated along the plane of the clarke belt will have less interference with adjacent satellites, but at our wattages that is probably not meaningful.

The most likely explanation for the original long .74-meter oval is that at the time, Hughes was both Direcway and DirecTV, and they offered an offset-LNB mount that would receive TV from the same dish for various internet assignments. The one that worked with 117 was way out there (16-degree spread) and would not have worked without a significantly elongated dish.

The need for multiple simultaneous satellite views is why TV dishes went from round to oval.
--
Motosat self-pointing dishes: .74 meter G74 on 127W, SL-5 HD DirecTV|Hughes HN7000S|Verizon UMW190 Air Card|1990 Blue Bird Wanderlodge Bus "Blue Thunder"|Author of hnFAP-Alert, PC-OPI and DSSatTool


grohgreg
Dunno. Ask The Chief

join:2001-07-05
Dawson Springs, KY
said by dbirdman:

Only the Hughes Ku-Band antenna is an oval, and they built a couple of different ovals, with later ones being "less oval."ous satellite views is why TV dishes went from round to oval.

I'm not sure how to interpret this, as Hughes doesn't actually build reflectors. They purchase both circular and ovoid variants directly from established reflector manufacturers, who may or may not paint Hughes name on it. I've got a 98cm Prodelin within line of sight right now,and it's about as round as it gets. Outside the US, they team with outfits like Avanti, Hylas, Tooway - which makes for even more dish selection. Then there's the Ka/Ku which was taller than it was wide. It's almost suggests an figure 8 shape. I think it's considered an ellipsoid. This one was fielded for a while, in the days leading up to fielding the HN9000. I guess it was a transitional thing, so that existing inventories could be used with either the 7000 series or the HN9000 series.

Don't quite follow your beam explanation, but I do agree that - like with the Ka/Ku dish - being able to use one dish for more than one application is simply good business sense. In most consumer grade satellite internet situations, it doesn't really matter whether a dish is round/ovoid/ellipsoid, any of the three will likely get the job done.

//greg//
--
HN7000S - 98cm Prodelin/2w "pure" Osiris - ProPlus - G16/1001H - NOC:GTN - NAT 67.142.115.130 - Gateway 66.82.25.10 - DNS 66.82.4.12 and 66.82.4.8 - Firefox 15/MSIE9 - AV/Firewalled by NIS2012


dbirdman
Premium,MVM
join:2003-07-07
usa
kudos:5
said by grohgreg:

Don't quite follow your beam explanation,

I probably should have used "pattern" rather than "beam," as the Wikipedia article on parabolic antennas does:

"Shaped reflectors - The parabolic reflector can be given a noncircular shape, and/or different curvatures in the horizontal and vertical directions, to alter the shape of the beam. This is often used in radar antennas. As a general principle, the wider the antenna is in a given transverse direction, the narrower the radiation pattern will be in that direction. "
--
Motosat self-pointing dishes: .74 meter G74 on 127W, SL-5 HD DirecTV|Hughes HN7000S|Verizon UMW190 Air Card|1990 Blue Bird Wanderlodge Bus "Blue Thunder"|Author of hnFAP-Alert, PC-OPI and DSSatTool

TexasRebel

join:2011-05-29
Edgewood, TX
reply to dbirdman
so the reason for using the oval dish on HNGEN4 is to produce a more narrow beam to the satellite when transmitting and not interfere with other satellites in adjacent orbital slots??

The ViaSat/Exede reflector is more round than oval and was wondering what kind of beam pattern it was sending to it's satellite.

Does the TX beam fan out the further out it goes or does it keep it's tight cylinder shape from ground to Sat??

I'm guessing it fans out like it does from the satellite. A spotbeam looks like it can cover around 250 mile diameter, though when it leaves the satellite it's only a couple feet in diameter??


dbirdman
Premium,MVM
join:2003-07-07
usa
kudos:5
In an ideal situation, the beam from a ground dish would be a pure cylinder, oval, or square that arrived at the satellite as the same size as the dish. In practice it is impossible, and in fact the beam from a large dish arrives more tightly focused than that from a small dish. Even a laser beam will slowly spread over great distances.

I haven't seen a Gen4 dish, so didn't know it was oval (if indeed it is). Could be because once again Hughes is associated with a TV company, and they could be looking at possible TV LNB attachments, who knows?

The size of the beam when it arrives at earth is all about focus - play with a magnum flashlight or similar and note how variable the beam can be even though it always leaves the flashlight at the same diameter. They can focus the antennas on a satellite to fairly small, or all the way out to full CONUS or more.
--
Motosat self-pointing dishes: .74 meter G74 on 127W, SL-5 HD DirecTV|Hughes HN7000S|Verizon UMW190 Air Card|1990 Blue Bird Wanderlodge Bus "Blue Thunder"|Author of hnFAP-Alert, PC-OPI and DSSatTool


chip89
Premium
join:2012-07-05
Independence, OH
Reviews:
·Cox HSI
The Gen4 dish looks like this.


grohgreg
Dunno. Ask The Chief

join:2001-07-05
Dawson Springs, KY
reply to TexasRebel
said by TexasRebel:

so the reason for using the oval dish on HNGEN4 is to produce a more narrow beam to the satellite when transmitting and not interfere with other satellites in adjacent orbital slots??

In an ideal world, perhaps. But don't make it more complicated than it really is. In the case of round versus oval in consumer grade satellite internet, I'm pretty sure the selection is much more financial than it is technical. They use the lowest price multi-purpose antenna that meets minimum ITU and FCC regulations.

//greg//
--
HN7000S - 98cm Prodelin/2w "pure" Osiris - ProPlus - G16/1001H - NOC:GTN - NAT 67.142.115.130 - Gateway 66.82.25.10 - DNS 66.82.4.12 and 66.82.4.8 - Firefox 15/MSIE9 - AV/Firewalled by NIS2012