T90 Limitations

[Acelon]

I probably should have noticed this by now, but I have discovered a limitation to the T90 dish that some might find interesting to know and that i haven't seen mentioned before.

It seems that your location can drastically effect how much true arc you can get, more than likely based upon how much you have to skew. Where I live, depending upon the range of satelites I entered into the satlex calculator, the skew given to me was between 65 and 71. I finally got my central satellite signaled in good so i go to add my two outside LNBs, and here is where I notice my problem. Even though the furthest east satellite is only 18 degrees from my center, the calculator says it goes to L-31! For those who dont have a T90, the LNB bar stops at 25. Turns out that my 3 furthest east sats were all over L-25. Just not going to happen unless i find a way to extend the bar(i've seen some examples of that in previous posts). Going back to satlex to recalculate and make sacrifices, I fiddled around with the two outer sats, and found that by shifting the central sat back to the east(declaring the east sat to be one even further than i wanted) I am able to get only a 36 degree arc that will fit between L-25 and R-25. Fortunately, I will probably only have to sacrifice one of the sats i was wanting, but still disappointing.

Bottom line, when choosing your satellites, dont just assume that if its within the 40 degree arc that it will work, make sure your R or L values are under 25 as well. Hope this helps.

P.S. is skew more related the latitudinal or longitudinal position? Just curious why my skew is so slanted in comparison to other installs ive read about(I believe iceberg was in the upper 70's)

 

[Anole]

It might help us understand better, if you would post your location, as well as the satellite locations you were using.

 

[Acelon]

I believe the link below will show you an example of what i mean. Notice that although all satellites listed are within the 40 degree arc, AMC3(87W) is the easternmost satellite that can be done without modifications.

SatLex Digital :: Technology :: Calculators :: WF Toroidal Calculator

 

[Acelon]

Just played around with satlex a bit, and maybe skew doesn't have as much to do with it as i thought. I just ran the numbers for pensacola for the same sat range, and got a less steep skew, but same issues.

SatLex Digital :: Technology :: Calculators :: WF Toroidal Calculator

 

[Acelon]

The problem looks to get worse as you travel West down I-10. I checked Biloxi, Baton Rouge, Houston, and El Paso, and the margin for error gets smaller and smaller. ElPaso only gets a range of 32 degrees.

I moved it further north, to Nashville and Dallas, and it gets better. Seems to be a function of how far south you live. That would make sense of why Iceberg didn't have this problem
Looks like Anole will have the opposite problem of mine, with the R side of the scale getting too big.

 

[voomvoom]

Use the SatLex as a guide. I think you'll find that you can get from 83.0w to 123.0w? Don't pay those R & L numbers much attention. I know I was able to get 87.0w to 129.0w with little problems. It's not the easiest thing to tune so many different lnbf's on one dish, but it is do-able. I've now got it tuned to 72.0w to 115.0w. It takes a lot of patience (which I have little of), but if I can do it. so can you. Don't just look at the number and see it says more than 25 and give up. Keep working with it. Good Luck..!!!

Edit: Sorry, but it's 113.0w, not 115.0w..... but you should still be able to get from 83.0w to 123.0w....

 

[Acelon]

But from looking at your settings(assuming near atlanta) I could get everything from 87 to 129 under the 25 mark with only a little manipulation. There is no way for me to do that due to being farther south than you. If the setting was 29, where would you place the LNB on your guide?

ok, i just checked 72 and 115 for your location(again assuming atlanta), and they do go way over. Where did you put the lnbs that are bigger than 25?
)
(LOL, just checked my own settings for your current sats and i go from L35 to R32. )

 

[jerryt]

P.S. is skew more related the latitudinal or longitudinal position? Just curious why my skew is so slanted in comparison to other installs ive read about(I believe iceberg was in the upper 70's)

Skew is a relationship between your true south satellite in the center of the T90 (Zero skew) and the distance to your desired center satellite. The further the distance the greater the skew.

As far as less then 40 degree arc when the T90 is skewed a lot, you are correct. Think of it this way with zero skew the LNB rail is X inches wide when measured horizontally. And less then X when tilted (skewed), still measuring horizontally.

Just buy two T90, works for me.

Satlex calculator has always been wrong at the outer LNB's for me, so only report actual results.

 

[voomvoom]

I'm in Middle Georgia near (west of) Macon @ about 32.6n x 83.9w. Do like jerry says, report actual results, not what SatLex says....

 

[Acelon]

That also makes a lot of sense on why it is worse the further south i live. The further south, the smaller the crosssection of cone the bar represents. This is turning into a good tutorial thread, everyone learns something new and contributes

Cant wait to get home and try some of this new theory out. Still a little confused on how to begin aiming an lnb thats outside the 25 though. Any suggestions?

Ohh, and I can't put up a second T90 under threat to my life, I'm on three strikes already. One for the amount of money i have already invested, the second for chopping down a large clump of her banana trees to clear a line of site, and the third for installing this huge dish in the back yard without telling her first(aparently she wanted to put a garden there or something). To say im on thin ice already is understating it

 

[Anole]

side boards

Someone posted some pictures with extensions to the ends of the LNB rails.
I don't recall if it was JerryT, Iceberg, or . . . ?
But some fellows just won't take "no" for an answer. - :up

 

[voomvoom]

Don't worry about that 25 number. Put your receiver on a TP from the outside satellite, or better yet, put it on a TP for AMC3 ku @ 87.0w, and move the lnbf around to you find it. You can find the outer ones later?

 

[Acelon]

Yea, i saw those and might try it in the future. I'll just go with what i got until i learn more i think. As long as i can get the Thai channels on 25 my wife will be happy, and i still got to figure out where to get some cricket feeds.

 

[voomvoom]

Yea, i saw those and might try it in the future. I'll just go with what i got until i learn more i think. As long as i can get the Thai channels on 25 my wife will be happy, and i still got to figure out where to get some cricket feeds.

Is this a typo? Do you mean T5/IA5/G25 @ 97.0w?

 

[Acelon]

LOL yea sorry, I missed the G in G25. Darn laptop keyboards

 

[glen4cindy]

I read some info from the Wave Frontier website, and the manual mentions that the twist of the LNB in the holder is the same as the position on the rail, is that correct?

I'm very close to ordering one of these and am a little worried about aiming everything especially now that I see that the Sat Lex site is not real correct.

Isn't part of the equation of getting everything lined up correctly dependent upon getting these outside LNB's zeroed in correctly? I remember Iceberg said this was the hardest part.

I'm also worried about the screwy skew for 103 that he mentioned. I am thinking that might be my center, but I have not decided yet. Actually, that was my first plan, but, I am going to use a 2nd dish for 123, because I can't bear losing my Equity mux!

 

[jerryt]

Still a little confused on how to begin aiming an lnb thats outside the 25 though. Any suggestions?

The outboard LNB's get a much weaker signal then the center. Best to not try and use the ends of the rail, unless it is a very powerful satellite.

 

[Wescopc]

I read some info from the Wave Frontier website, and the manual mentions that the twist of the LNB in the holder is the same as the position on the rail, is that correct?

I'm very close to ordering one of these and am a little worried about aiming everything especially now that I see that the Sat Lex site is not real correct.

Isn't part of the equation of getting everything lined up correctly dependent upon getting these outside LNB's zeroed in correctly? I remember Iceberg said this was the hardest part.

I'm also worried about the screwy skew for 103 that he mentioned. I am thinking that might be my center, but I have not decided yet. Actually, that was my first plan, but, I am going to use a 2nd dish for 123, because I can't bear losing my Equity mux!

You do twist the LNBF holder a little to better aim them towards the center of the dish, it is easy to do. There are markings on the holder, pretty much set and forget. You zero in the skew of the dish with your outside LNBFs. You can set the individual skew separately within the holder of the LNBF. So it won't mater with AMC1 (103W) whether it is your center satellite or not. T-90's are one ot the more difficult dishes to set up, but if you do them one step at a time - they are great.
Bob

 

[glen4cindy]

The outboard LNB's get a much weaker signal then the center. Best to not try and use the ends of the rail, unless it is a very powerful satellite.

I don't recall this being the experience of Iceberg when he set his T90 up.

How much weaker of a signal?

Don't the outboard LNBF's help get the skew of the dish just right?

 

[glen4cindy]

You do twist the LNBF holder a little to better aim them towards the center of the dish, it is easy to do. There are markings on the holder, pretty much set and forget. You zero in the skew of the dish with your outside LNBFs. You can set the individual skew separately within the holder of the LNBF. So it won't mater with AMC1 (103W) whether it is your center satellite or not. T-90's are one ot the more difficult dishes to set up, but if you do them one step at a time - they are great.
Bob

So, each LNBF needs to be skewed just as if it were a stationary dish?

The Sat Lex site didn't mention skewing each LNBF. Is there a website that tells you how much skew you need in each one per your location?

I suppose this could also interfere with how close you can get the LNBF to each other.