lnb and dish setup (1 Viewer)

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mick d

SatelliteGuys Family
Aug 12, 2009
62
0
ne texas
I have a 10 ft mesh dish with a center lnb support that i can adjust in or out. I have geosat lnbf mounted, so when I got the dish i just mounted the lnbf on the existing mounting distance and had to move lnb in ( was about 3" sticking out from scalar ring). I thought since the lnb should stick out about 1/4" then I could move the support in and move the lnb back to get my 1/4" sticking out from scalar and I would get a much better signal. It didnt work so then I did my calculations and got a f/d of 48" but still not a good sig. Any suggestions on distance of scalar ring and why I got my better signals with the lnb sticking out 3 to 4 inches in front of the scalar? Also any suggestions on the best lnb without a servo?
 
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badmotorscooter

SatelliteGuys Family
Sep 28, 2008
42
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Indy
I am not sure which 10ft dish you have but perhaps your calculations are off. If you have the Geosatpro C2 lnbf then make sure it is rotated 90deg. so that the 0 mark is facing 9 or 3 o' clock when mounted in the scalar ring. Here is a list of dish specs that might help you with your f/d settings.



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mick d

SatelliteGuys Family
Aug 12, 2009
62
0
ne texas
Thanks bad, Lots of good info there I will go over it and readjust. I did stretch string from 4 points on dish to get my center and it was dead center, and measured from the string to the center of dish and got 20". So my measurements were 124"x124"/ 16x20"= 48.05" or 4 ' which is where I set my scalar. Maybe the wrong formula after looking at chart, trying to figure out the fd according to it.
 

tradewinds

SatelliteGuys Family
Jan 3, 2006
102
0
Central Florida
Got a question, from that list above, if the column "Motor Arm Length Required" states 18", does that mean a 24" arm would not work or is 18" minimum?
 

Lak7

SatelliteGuys Master
Pub Member / Supporter
Feb 28, 2008
5,451
7
Near Chicago, Illinois
What limits the Unimesh is the Main Axis Bar, the Actuator can and will hit it if the Limits are not properly set. And when it hits, the Arm is trashed.
 

tradewinds

SatelliteGuys Family
Jan 3, 2006
102
0
Central Florida
what is the best way to go about setting the limits on the actuator? Can this be done via the actuator alone or does this need a receiver to do it and if so what is the process?
 

B.J.

SatelliteGuys Pro
Oct 15, 2008
2,029
1
Western Maine
I have a 10 ft mesh dish with a center lnb support that i can adjust in or out. I have geosat lnbf mounted, so when I got the dish i just mounted the lnbf on the existing mounting distance and had to move lnb in ( was about 3" sticking out from scalar ring). I thought since the lnb should stick out about 1/4" then I could move the support in and move the lnb back to get my 1/4" sticking out from scalar and I would get a much better signal. It didnt work so then I did my calculations and got a f/d of 48" but still not a good sig. Any suggestions on distance of scalar ring and why I got my better signals with the lnb sticking out 3 to 4 inches in front of the scalar? Also any suggestions on the best lnb without a servo?

I'm reading this thread a bit late, but just had to comment on a couple things. I assume it was just a typo, but the 48" is not the f/d, that's got to be the focal length, assuming that you've done the calculations right. That would calculate to an f/d of about 0.4. And that focal length is NOT where you position the scalar ring, that should be measured to about 1/4" inside the throat of the feedhorn. And although in many cases, it's easier to adjust the focal length by moving the throat of the feed inside the scalar ring, the correct procedure is to first set the position of the feed in the scalar, based upon the f/d, THEN, position the scalar so that the throat of the feed is at that 1/4" less than the focal length. This is not easy, since it usually means adjusting 4 feed support arms , 3 of which are often out of reach. What I have done (which I don't really recommend, but it's easy), is to loosen the bolts that connect the scalar to the support arms, then twist the whole scalar so that the support arms come in more tangentially than radially. This effectively reduces the focal length adjustment, and twisting the other direction so that the support arms come in radially toward the center makes the focal length adjustment longer. Again, I don't recommend this, but it's the only way I could find to do the adjustment without a major effort to get to the very top support arm connections to the dish, which on my spinclination IS dooable, but it's still a major project, and I'm lazy.

Anyway, I got the impression (maybe wrong) that you were leaving the position of the fixed at the focal length position, and moving the feed in and out for best signal. This isn't proper, and if done this way, I think you might be peaking on a side lobe instead of the main lobe. You might check to see if when on your south sat, you get two apparent peak positions when adjusting the elevation setting on your dish.
 

badmotorscooter

SatelliteGuys Family
Sep 28, 2008
42
0
Indy
I need to tweak my f/d as well. Unfortunately I busted the set screw mount from the scalar ring on my c2. I was able to epoxy it back in place. I also glued the feed horn in place at according to where my chaparal feed horn stuck out. Anyway my thought was I can adjust the distance by using washers under each leg on the dish to move it out, or shim the scalar ring with washers behind it to move it closer. So far though I am able to pick up channels on each sat from 55.5w to 127w with some peaking at 82% according to my coolsat 6000. I am sure I have more work to do but this weather sucks here and I am content for now.
 

mick d

SatelliteGuys Family
Aug 12, 2009
62
0
ne texas
thanks bj, I have the center support for the lnbf which I can slide in or out and just tightened a clamp ring down to secure it. Im thinking it was close to where it should be when i got it. I was wanting to just max out my signal the best i could and i got my best signal with the lnb sticking out of the scalar about 3 inches. I thought this was not right seeing as all the pics i saw showed the lnb sticking out about 1/4 inch so i slide the support arm in closer to dish and slide lnb back closer to scalar to where i thought it should be, this was not good. So i calculated the f/d for my dish which i was thinking was my distance for my scalar which was 4', but from what ya told me that is not right. I'm thinking if I can set my lnb distance from scalar right then it would be easy enough for me to slide the support arm in or out to get my best signal. Also is the geosat a decent lnbf or is there a better non servo lnbf?
 
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mick d

SatelliteGuys Family
Aug 12, 2009
62
0
ne texas
I may have it wrong but from what I can see by my calculations is 4' depth with a .40 f/d ratio which is how far the lnb sticks out from the scalar. This is not even close to getting me a signal.
 
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