Lnb boom are seems to be to long!

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I have been going mad in trying to get my Gibertini 1.5 to tie up with the maths.

3°W is my zenith sat, it's elevation is 31.6° the Gibertini 1.25 & the 1.5 has an offset value of 21.3° so my dish face has to be 10.3°

Every time I set the dish face to 10.3° I get no signal! So I put the 1.25 on the mount and set it up to 10.3° and bingo I have max signal.

But on the 1.5 dish no signal, so I checked all the pole angles/level and that was ok. My polar mount is set to the correct elevation of 38.8°

Satellite elevation is 31.6° + 6.7° (magnetic declaration angle) = 38.3°

So in the end I started to play with the lnb position and have found the the boom arm is about 5mm to long!

Has anyone else ever come across this? Or am I barking up the wrong tree?
 
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5mm extra (oooooer) on a 1.5m reflector will equate to about 2% under or over illumination but not a major loss of performance. You should also have the lnb throat adjustment to compensate. The Gibertini 1.25m has a twin boom from memory, all others are one piece. There is no other from the range that will fit on the 1.5m dish.
 
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Channel Hopper said:
5mm extra (oooooer) on a 1.5m reflector will equate to about 2% under or over illumination but not a major loss of performance. You should also have the lnb throat adjustment to compensate. The Gibertini 1.25m has a twin boom from memory, all others are one piece. There is no other from the range that will fit on the 1.5m dish.
Click to expand...
Yeah the 1.25 has a twin boom arm, meeting at the lnb holder. And the 1.5 is a single arm.

But on new photos of the 1.5. They seem to have changed the lnb holder, from the one I have. (It looks like the 1.25 holder.

But when I lower the lnb, I can add up to 2.5db!

But I am so glad I finally found what is out, and why the maths don't tie up. (I get a bit ocd with numbers they have to tie up) or it will really get to me!
 
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Which pictures ? the Gibertini site only has one design of feed for the 1.5m and only one picture last time I looked
 
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Chris, not sure where you are coming from ( no comments from others )
The other day of off topic you posted you were happier!
" I have done a fair bit of tweaking today and quite happy. But I still have a few more things to sort out. "
Off Topic Chatter 2016

Ignore the maths, and the level or inclinometer you are using. If you adjust the dish to max on 3W and it tracks the arc, what is the problem?
 
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Channel Hopper said:
Which pictures ? the Gibertini site only has one design of feed for the 1.5m and only one picture last time I looked
Click to expand...

If you look at the lnb holder in the photo below image.jpeg
You can see it is the same as the 1.25 lnb holder.

And not the same one I have
 
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Llew

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Channel Hopper said:
I need to see something slightly closer up.

The Gibertini site image looks like the same

http://gibertini.it/images/antennas/Banner150_EN.jpg

The 1.25 comes in two shapes, LP,

http://gibertini.it/images/antennas/125LPsupporti.jpg


and L

http://gibertini.it/images/antennas/Banner125L_EN.jpg

Neither look like the one you have
Click to expand...
The second link dish is the same as my Giggy 1.25, i.e. with a single arm and LNB holder as shown. It needs a seperate AZ/EL mount, unlike the twin arm version, which incorporates AZ/El adjustment.
 
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OK, there we go again! :rolleyes:
Chris1979 said:
Every time I set the dish face to 10.3° I get no signal!
Click to expand...
That clearly says, at least to me, that LNB's Phase center is not co-located with antenna's Focal point. Did you try to measure the dish and find out where its Focal point located? Chris1979.jpg
Trow away LNB-holder you have right now and create something like this (not necessary from INOX) IMG_20160228_113701.jpg , with it you will be able to find proper position of LNB.
 
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Gibertini has been making decent dishes for years. It looks more like somebody has mixed up feeds in a warehouse somewhere.
 
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