Ku arc info (1 Viewer)

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putney

Thread Starter
SatelliteGuys Pro
Aug 12, 2009
854
6
St Louis, missouri
I am at 89.6ºw

The sats closest to my true south track fine. As I go out in either extreme USALS doesn't hit it's mark.

example:

72ºw peaks at 72.7ºw

125ºw peaks at 124.2ºw

Using the attached diagram, I'm thinking that I have to much declination combined with low elevation. That would put the most southern sats on track and pull the extremes toward the middle.

Am I reading that right? When on the pole I always seem to do the opposite of what is needed, so I thought I'd ask first.

Thanks.
 

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Lak7

SatelliteGuys Master
Pub Member / Supporter
Feb 28, 2008
5,451
7
Near Chicago, Illinois
When on the pole I always seem to do the opposite of what is needed
Yep, same here. :)
So, with that in mind, I agree with your "I'm thinking that I have to much declination combined with low elevation."
 

beavs2112

Addicted to Legal FTA
Jan 28, 2010
814
247
London Ontario Canada
Hi putney. i have only installed one fta dish (my own) so i don't have lots of experience. in all deference to lak7 i disagree. it seems to me if you had two misalignment errors (both azimuth and elevation) you wouldn't trac the center of the arc either. look at both diagrams for elevation errors. if you are off in elevation you only get sats at the extreme ends of the arc. my humble suggestion is to move both the dish and motor slightly to the west. it seems you are only off by 0.8 degrees.
 

putney

Thread Starter
SatelliteGuys Pro
Aug 12, 2009
854
6
St Louis, missouri
Hi putney. i have only installed one fta dish (my own) so i don't have lots of experience. in all deference to lak7 i disagree. it seems to me if you had two misalignment errors (both azimuth and elevation) you wouldn't trac the center of the arc either. look at both diagrams for elevation errors. if you are off in elevation you only get sats at the extreme ends of the arc. my humble suggestion is to move both the dish and motor slightly to the west. it seems you are only off by 0.8 degrees.

But if you look at it, low elevation would pull everything down, then to much declination would push the center on track. Both sides are equally off towards the center by .8

If I rotate then one extreme would be one the mark and the other would be pulled in further.

That's my thinking anyway. :confused:
 

beavs2112

Addicted to Legal FTA
Jan 28, 2010
814
247
London Ontario Canada
those darn diagrams are confusing to me sometimes. but now that i take a second look i have changed my mind. i think both you and lak7 are correct. hope it turns out well for you :)
 

B.J.

SatelliteGuys Pro
Oct 15, 2008
2,029
1
Western Maine
I am at 89.6ºw

The sats closest to my true south track fine. As I go out in either extreme USALS doesn't hit it's mark.

example:

72ºw peaks at 72.7ºw

125ºw peaks at 124.2ºw

Using the attached diagram, I'm thinking that I have to much declination combined with low elevation. That would put the most southern sats on track and pull the extremes toward the middle.

Am I reading that right? When on the pole I always seem to do the opposite of what is needed, so I thought I'd ask first.

Thanks.

In my opinion, those charts like you posted don't give you ANY information regarding what you're asking. Those charts don't tell you anything about whether the USALS angle numbers will be spread out more or less along the arc. Those examples are just showing examples of you being off the arc, and they are only a qualitative way of determining _IF_ your are on or off the arc, and IF you ARE OFF the arc, they can help you determine what corrections you need to get back on the arc, such as by lifting and pulling down in the center and at the 2 extremes to see if the signal improves or doesn't improve.

Ie before you start making corrections, you should first determine whether or not you are on or off the arc.

In general, if you can peak to maximum signal just by bumping the motor in diseqC-1.2 mode or by changing the sat longitude in USALS mode, then, I would have to conclude that you are on the ARC, and you shouldn't be making ANY corrections, and that either the motor isn't going to the right place or the receiver isn't sending the right USALS angles.

HOWEVER, you haven't given enough information to determine whether or not you are on the arc or not. Basically, I would peak on those 2 sats you mention and also on your true south sat, and lift up, pull down the dish, and see if the signal improves or gets worse. IF any of the 6 tests give improvement, then you are off the ARC. If all 6 tests show the signal getting worse, then you are on the arc at least as close as you can get given the sensitivity of your receiver's meters.



Basically, don't try to fix what isn't broken. Looking at your numbers, my feeling is that if you were off the arc enough to give those numbers, that you'd have to be so far off alignment that you probably wouldn't even see those extreme sats, so I'm really guessing that either the motor or receiver is at fault.
I can't remember what receiver you're using, but some receivers will tell you what USALS angle it's turning to, given your lat/lon. If your receiver gives that info, then compare that number to the number given via one of the USALS angle calculators.
 
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