Cband Alignment - Help

iBoston

iBoston

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I decided i need to digress a bit. Here is my situation. I have a 10 foot button hook cband dish, my first, and its performance is sub optimal and I'm trying to figure out WHY? - I believe it has something to do with the LNBF and its alignment. Visually, it looks like it might be a bit offset. I am thinking i got into a situation of chasing the fine tuning in the wrong way.

Let me run something through my head to you guys. If i have the lnbf mis-aligned, then fine tuning the main dish to a signal would then fine tune me to a false max. Is this true? It seems to me that maybe i have to somehow better align the LNBF before then attempting to fine tune on the dish, other wise, I'm chasing a false max. Does that make sense..

I guess, I'm trying to get back to the basics.... How do wipe away any doubt that I am not fine tuning this dish correctly so that i can obtain the best signal possible. This is not a ARC tracking issue. I am tracking the ARC fine, but, i seem to be equally sub par on many TPs through out the ARC. TP's that I remember once not having issues with.

I appreciate the input....
 
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Brct203

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I think your reasoning makes sense. I would start by a string test, then centering the feedhorn so that it's same distance form all points of the rim of the dish. Then make sure it's aiming to the center of the reflector. Then the focal length. You might need to adjust the dish declination to compensate for any change in LNBF north-south position. Likewise,the positionner counts might be slightly off.

Now, there's one point that is not always clear to me. With the typical scalar/feedhorn setup, the arms are attached to the scalar and the feed can get adjusted. As far as I understand it, this affects both the F/D setting and the focal length at the same time. Isn't that a bit problematic? If the arms are not perfectly adjusted, you could be in a situation where you get the right focal length but the f/D is wrong, or vice versa, but you don't know. Thoughts on this?
 
phlatwound

phlatwound

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...Now, there's one point that is not always clear to me. With the typical scalar/feedhorn setup, the arms are attached to the scalar and the feed can get adjusted. As far as I understand it, this affects both the F/D setting and the focal length at the same time. Isn't that a bit problematic? If the arms are not perfectly adjusted, you could be in a situation where you get the right focal length but the f/D is wrong, or vice versa, but you don't know. Thoughts on this?

Yes, back to basics exactly as Brct203 said, that is where I would go.

And Brct203, I think with the typical 3 or 4 arm feed holder you are correct, of course with a buttonhook you can easily adjust focal length and F/D ratio independently of each other. As long as your focal length is good with a "milkstool" support you are golden but if it's off you won't get things "perfect", you have to figure out how to adjust the focal length.
 
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Need2learn

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I decided i need to digress a bit. Here is my situation. I have a 10 foot button hook cband dish, my first, and its performance is sub optimal and I'm trying to figure out WHY? - I believe it has something to do with the LNBF and its alignment. Visually, it looks like it might be a bit offset. I am thinking i got into a situation of chasing the fine tuning in the wrong way.

Let me run something through my head to you guys. If i have the lnbf mis-aligned, then fine tuning the main dish to a signal would then fine tune me to a false max. Is this true? It seems to me that maybe i have to somehow better align the LNBF before then attempting to fine tune on the dish, other wise, I'm chasing a false max. Does that make sense..

I guess, I'm trying to get back to the basics.... How do wipe away any doubt that I am not fine tuning this dish correctly so that i can obtain the best signal possible. This is not a ARC tracking issue. I am tracking the ARC fine, but, i seem to be equally sub par on many TPs through out the ARC. TP's that I remember once not having issues with.

I appreciate the input....
Hello here's what you do, start with the string trick to make sure your LNB in pointing to the center of the dish, and when the dish is at it highest point the LNBF should be straight up and down. Next check your elevation by push down on the dish when having a signal meter connected to the LNB see is the signal gets any stronger or weaker, next do the same by picking up on the dish.

Last check your declination and make sure it is correct.
 
iBoston

iBoston

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and when the dish is at it highest point the LNBF should be straight up and down.

Not sure what you mean by this line. Please explain further... Thanks

Also, just for Clarity, when you mean dish at its highest point, your referring to my Top of Arc position... Correct.
 
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Need2learn

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Not sure what you mean by this line. Please explain further... Thanks

Also, just for Clarity, when you mean dish at its highest point, your referring to my Top of Arc position... Correct.
when you. move the C band turn the dish until it is pointing straight up like for me it is like 101w the dish is at its highest point. once you are there look at the front the LNBF it should be straight up and down..
 
Titanium

Titanium

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Depending on the brand and model, at the apex or top of the arc (arc position is equal to your longitude position), the zero "0" skew marking on the LNBF will either be aligned with 12/6 o'clock (Vertical Axis of the reflector) or 3/9 o'clock (Horizontal Axis). The Skew marking on a LNBF is not always referencing the vertical probe.

If the dish is properly tracking the arc and the feedhorn is confirmed to be centered on the reflector and you are seeing signal level variations on specific transponders, this likely indicates an incorrect FD/FL setting. Sidelobes and the main beam shaping may be inadequately attenuating signals on adjacent satellites.
 
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iBoston

iBoston

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I won't be able to put into action anything discussed here until i clear the cold running through our family at the moment. I truly hate being sick. At least for once, everyone in the family is sick at the same time, which makes it easier...
 
Captain Midnight

Captain Midnight

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Depending on the brand and model, at the apex or top of the arc (arc position is equal to your longitude position), the zero "0" skew marking on the LNBF will either be aligned with 12/6 o'clock (Vertical Axis of the reflector) or 3/9 o'clock (Horizontal Axis). The Skew marking on a LNBF is not always referencing the vertical probe.

If the dish is properly tracking the arc and the feedhorn is confirmed to be centered on the reflector and you are seeing signal level variations on specific transponders, this likely indicates an incorrect FD/FL setting. Sidelobes and the main beam shaping may be inadequately attenuating signals on adjacent satellites.
When you say variations, do you mean certain transponders' signals not peaking in the same position as the majority on the bird? I have a limited few on one satellite that only lock when I tap the dish a hair to the east.
 
Captain Midnight

Captain Midnight

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I won't be able to put into action anything discussed here until i clear the cold running through our family at the moment. I truly hate being sick. At least for once, everyone in the family is sick at the same time, which makes it easier...
Hope you feel better soon. I have only had a BUD for 17 months but I suggest you move your dish to the actual zenith point. I live at 92°W so I just click a bit west of 91w until my dish mount appears to be facing straight up.

Take an inclinometer or angle finder to check your declination angle vs the angle your LNBF is pointing toward your dish center. It has happened to me that my LNBF ends up pointed downward a full degree compared to my declination angle after adjusting LNBF skew. Those 2 angles should match. I make sure to get mine within 0.1° of my declination angle. That is something I don't recall in the few setup guides that I have read.

If you don't know your exact f/D, then go ahead and figure that out during your string test.
 
iBoston

iBoston

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I'm feeling much better today.. I am gonna get my butt outside, but for different reasons today - I have to remove another dish (120cm) that came down from our thunderstorm a few days ago, and i have to do some fencing repair that the cows damaged, and to top it off, we had frost last night (latest in well over a decade), so ill have to check out how the tomatoes and peppers fared..
 
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Need2learn

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Let us know what you find out about it.. Trust me I have my C Band dish up on my garage it is a pain in the neck to get up there and do adjustments, been there two many times..
 
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iBoston

iBoston

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And to top it off, we had a rotten smell coming from our water we noticed when we showered. Lifted up the shallow well cap today with the tractor and found a dead snake in there. :facepalm Fished out the snake, poured a couple cups of bleach into the well, and tractor'd the well cap back on. There is a first for everything....
 
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wvman

wvman

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I decided i need to digress a bit. Here is my situation. I have a 10 foot button hook cband dish, my first, and its performance is sub optimal and I'm trying to figure out WHY? - I believe it has something to do with the LNBF and its alignment. Visually, it looks like it might be a bit offset. I am thinking i got into a situation of chasing the fine tuning in the wrong way.

Let me run something through my head to you guys. If i have the lnbf mis-aligned, then fine tuning the main dish to a signal would then fine tune me to a false max. Is this true? It seems to me that maybe i have to somehow better align the LNBF before then attempting to fine tune on the dish, other wise, I'm chasing a false max. Does that make sense..

I guess, I'm trying to get back to the basics.... How do wipe away any doubt that I am not fine tuning this dish correctly so that i can obtain the best signal possible. This is not a ARC tracking issue. I am tracking the ARC fine, but, i seem to be equally sub par on many TPs through out the ARC. TP's that I remember once not having issues with.

I appreciate the input....
I worked on a few button hook feeds where the tubing used to make them should have been heavier, leaving them drooping a bit.

This misalignment can be corrected by attaching a small diameter piece of aircraft cable 90 degrees apart around the dish, attached to the scalar on one end, the dish at the other, with a small turnbuckle in between.

It also allows for small adjustments on the focal point. I posted a photo of a tool I made on the lathe that went into the feed throat about an inch containing a laser I purchased off EBay.

I machined a hole in it at center, that was a few thousandths under the outside diameter of the laser body to hold it securely in place. It simplified setting the feed to dead center on the dish.

It can also be used to see if the feed is canted to one side or the other. I stuck a piece of duct tape over the center hole in the dish so you could see the laser. I know it sounds a bit overkill, but when you have 8 dishes, it's a handy tool.

If the string test is OK, you should be OK with the cables and turnbuckle, even without a laser tool. :)
 
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Need2learn

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And to top it off, we had a rotten smell coming from our water we noticed when we showered. Lifted up the shallow well cap today with the tractor and found a dead snake in there. :facepalm Fished out the snake, poured a couple cups of bleach into the well, and tractor'd the well cap back on. There is a first for everything....
Now all you need is for Samuel Jackson to say I am sick of these "" """ snakes lol
 

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