Weird encounter of the FTA kind

[Skyscanner]

I have a P* 1.2M aimed at 97 W. Been wanting to modify it so that I can add several sats, and since today was so nice, I thought I might try to add a CK1 to try my hand at a minibud project, wanted to add AMG. I added a crossbar, took out the bottom support and replaced it with a piece of 1/2" conduit. Wanted to do it so that I didn't ruin any of the old stuff so I could put it all back to orignial if I want to. Long story short, I never did get the minibud to work, so just before I quit for the day, I put a KU LNB in a clamp and tried to aim it. I couldn't get anything, so I kept watching the Q meter while I moved it all around. I finally got it to work, but am blown away by where it's aimed. It's aimed at the bottom 1/4 of the dish, where originally it was aimed in the center of the 4 bolts. Weird. I had checked the Q before I started the mod and it is exactly the same now. I wouldn't blame anybody for not believing this, I can't believe it myself! Originally the LNB had a 33 1/2" focal, now it's 28. Can't wait to get some more clamps and thread rod and try again.
Sky

 

[guapoharry]

Where do you measure from / to?

From the feed mouth to where? To the center of the dish? Along the axis of the feed? Where?

Curious

 

[Skyscanner]

Harry,
Along the axis of the feed, from the front of the feedhorn to the point of contact on the dish.
Sky

 

[Mikey11]

that means your dish elevation is set too low, the lower you aim the LNB the higher it will aim in the sky, you need to raise the dish elevation and aim the LNB higher also,

 

[Skyscanner]

Mikey,
That's another weird part, the dish was set on 97W before I started, the az and el did not move, only the side arms, they lowered the mount when they spread apart, the thread rod is a little over 6" long to compensate for the amount they lowered. Pic #3 shows the KU LNB in its new operating position with an angle that looks parallel to the lower arm and the focal point in the center of the lower part of the dish instead of its former spot in the center of the 4 mounting bolts. Later today I'm going to retry the CK1 to see if I can get Q in the same spot the KU LNB is now.

 

[B.J.]

With the focal distance off by as much as you say, you're probably peaking on a side lobe, as the center lobe will go away as the focal distance becomes off. Ku dishes display very wierd behavior when you peak on a side lobe.

 

[Skyscanner]

BJ,
You're right about the side lobes. I abandoned my attempts to mount a ck1 because the mount is too fliimsy for it, but I did mange to put the KU lnb in the correct focus in the center of the 4 mounting bolts at the proper angle and focal length. Getting 93-94% on RT. Next week I'll start adding more sats to it.