Need help aiming huge BUD with 3 point mount

[radiogooroo]

I'm new to the forum. I'm a broadcast engineer for a few radio stations in Houston, and a BUD with a 3 point mount is whipping me.

The dish is a Scientific Atlanta 8005. It's a 4.6 meter dish - huge - and in surprisingly good shape given its age and our humidity. I'm trying to get it aimed at AMC 8, the bird that carries most of the big radio networks (Premiere, Citadel, Dial Global, etc.)

This dish has a 3 point mount instead of a regular pole mount. I've aimed several C band dishes before, but this thing is throwing me for a loop. Usually, I just set the elevation with an inclinometer, then get the rough azimuth with a compass and move the dish back and forth slowly until it locks. Can't do that with this one.

It has 3 legs, and one large adjustment screw that you bolt to each leg to move it - one at a time. I've tried doing that somewhat randomly, and was able to see satellites with a spectrum analyzer, just not the satellite I'm looking for.

Does anyone have experience pointing one of these dishes with a 3 point mount? Would you be able to give any pointers? This thing is turning into a headache and a half, and I can see why it was abandoned in the first place.

 

[Anole]

Is there a manufacturers alignment manual on line?
Can you post a couple of pictures of the brute?
We do have some commercial professionals on line, so one of them may have experience with a similar dish.

I've seen a number of fixed commercial mounts, and none register with your description.
So, I can't imagine why there would be any trouble getting the azimuth set..
... then it's just a matter of elevation.
Doubt you'd let skew give you fits. :up

edit:
you say it's old.
did you clean the wasp nest out of the feedhorn? -
if it's been off-line for a while, maybe a good physical inspection is warranted.

 

[radiogooroo]

Is there a manufacturers alignment manual on line?
Can you post a couple of pictures of the brute?
We do have some commercial professionals on line, so one of them may have experience with a similar dish.

I've seen a number of fixed commercial mounts, and none register with your description.
So, I can't imagine why there would be any trouble getting the azimuth set..
... then it's just a matter of elevation.
Doubt you'd let skew give you fits. :up

edit:
you say it's old.
did you clean the wasp nest out of the feedhorn? -
if it's been off-line for a while, maybe a good physical inspection is warranted.

No documentation of any kind online that I've been able to find. The closest thing I've been able to find is some company that's trying to sell a manual for it for $40.

Bought a brand new Norsat 3220 PLL LNB for it. Disassembled the feedhorn and cleaned everything out of it. There was an unbelievable amount of nesting material under the feedhorn cover. It's good to go and set for the proper polarity.



Sorry about the tilted pics. The forum software is doing that.

 

[Beano_face]

cool dish...

seems like overkill if all you are after is the radio stations on amc8. a 10 or 8 footer would do you fine...

 

[radiogooroo]

cool dish...

seems like overkill if all you are after is the radio stations on amc8. a 10 or 8 footer would do you fine...

Actually, the minimum spec to receive the feeds from Premiere, Citadel, etc. is a 3.8 meter, 2 degree compliant solid dish, but that's not why we want to use this. It already exists, and it should be able to do the job. If we have to install a new dish, either on this parking garage or on the roof of our 11 story building, we have to bring in a structural engineer to satisfy the landlord.

 

[turbotoy]

I've noticed several of those dishes over the years, and always wondered how they were aimed at different birds without it being a complete nightmare.

If it were me, I would do the trig or model the mount in Pro/Engineer to determine the required link lengths. However, I'm a mech-e with a decent amount of mechanism design experience, and approaching the problem that way isn't exactly trivial.

My bet is that the tech manual contains some very useful lookup tables and/or equations.

 

[phlatwound]

Approximately how many degrees of azimuth do you need to rotate?

I'm sure it wouldn't be "easy", but would it be possible to remove the anchors, rotate the whole frame the dish is mounted on, then re-anchor?

 

[Anole]

What a monster!
I'll bet the frame was laid out on the ground, with a particular bird in mind.

Can't really wrap my head around the 3D-ness of that octopus with just the one rear view.
We are pretty good at solving problems, but to proceed, you'd need to post several pictures of the rear, from different directions, and showing the WHOLE dish/mount/base structure.

Assuming you're not too far off the desired bird / orbital location now, here's what I'd do:
- set an inclinometer on the back side of the dish to measure elevation and have someone monitor it while I cranked on the dish.
- likewise, it should be possible to rig a pointer along the axis of the dish (how, we've yet to decide), and have someone monitor that with a compass.
- then fiddling the jacks around, you should see from the helpers which way you are going, and be able to inch toward your known azimuth and elevation.
- once you think you are close, only then would I worry about watching a receiver or spectrum analyzer.
Don't think I would be afraid to tackle that, with a fair confidence of success. - :up

However, knowing how far off the dish needs to be from original, would be valuable.
The extra pictures from different angles are a must.

Sure hope to heck one of our professionals has a manual or the know-how to help ya better.

 

[sergei]

I rotated the picture for a better look, one heck of a bottom frame.

I'd say depending on what satellite it's aimed at now he going to need a small army to move it to the correct position as that's a heavy looking frame.

 

[Anole]

Yea, I rotated my copy here too, but it's still too zoomed-in for me to know what I'm looking at.
The front view suggests there's a hell of a structure behind the dish !

After discussion with some other members, I don't even know if or how much you can tweak the azimuth.

 

[sergei]

From just looking at the picture I can't see why it's going to be that hard to set up, other than having the man power to rotate the entire dish frame towards the correct satellite that he wants, it's nothing more that a fixed dish, just bigger.There's only 3 adjustable legs and one fixed and just by looking at them I can see how each arm can move the dish. He probably just needs something besides a spectrum analyzer, maybe a satellite meter or a receiver and TV out there to set it up, get on the satellite, find any signal and then start adjusting. From what he posted he has not yet found the right satellite.

 

[Bongu]

I can see how the mechanism allows for some azimuth adjustment, but to me it appears that there might be only 5 or 6 degrees allowed. What bird was this initially set up for? This info will be needed to determine if the frame needs to be moved. There should be a manual for the mount somewhere on the 'net. Just looked at the rotated pictures and see that the pad is large enough to move the frame with no problem.

The compass point method previously mentioned will probably be the easiest method to aim this big boy at the right bird. There has to be some point or marking on the frame/mount that can be used to determine the azimuth setting. Knowing the bird it was installed for would be a tremendous help and allow someone to identify this point on the mount/frame.

 

[Lone Cloud]

Noting that it was designed from the ground up to be a fixed mount dish. I doubt it was designed to look at 139w. Probably looks at a satellite in the low 100s

So it appears that if you want to point it at that bird, you have to redesign it.
It doesn't appear from the photos that you are going to be able to just make some adjustments with a wrench.

Looking at the photos, raising and lowering the dish angle looks possible with the back legs - if the steel there (the square steel fits inside the other square steel)
isn't rusted together, but turning the dish does not look easy, unless you could pivot that rusted steel it sits on. Either that or if you could get a round metal plate under the legs, you could turn it on that - sort of a lazy susan type concept.

If you can't pivot the rusted bottom steel, or find a big round steel plate, you might be able to do it with two small lengths of steel I beam - Maybe bolt the front two legs to one, and bolt the back leg to the other. Then pivot the I beams on top of the rusted steel, then weld or bolt in place when you have it aimed. Raising the whole thing six or eight inches shouldn't affect any aiming.


Good luck

 

[comfrey]

If you find that the current position of the dish is close to 139W you could try adding a second LNB at an offset. The dish is probably large enough to satisfy the requirement despite the loss of Q.

 

[arcticracer]

Adjusting Dish

We maintain many 4.5 meter dishes mostly Andrew, they are the standard system in small Alaskan villages. They are much easier to adjust than what you have here, we have a single adjustment for AZ and another for EL. Loosen a few locknuts, and rotate the struts with a big pipewrench.