One Meter Primestar Mini-Bud Experiment

[Anole]

room for errors

1). are you tracking the arc? or are you just concentrating on the elevation for South right now?
2). from what you are saying the motor latitude scale is a little off. Or maybe you've clamped the bracket too tight at the top or bottom, causing it to be elevated or depressed (?)
3). it's always possible the dish's elevation (LNB location) is not perfect.
When you put the C-band LNB on there, you'll have to fight hard to keep it same as now.

 

[Wescopc]

BTW, the axis of the motor shaft always stays parallel to the earth's axis (no declination at the motor's shaft). I drew a diagram:
http://www.satelliteguys.us/893654-post29.html
over a year ago trying to help jagee figure out his motor. Maybe help, maybe further confuse.
Bob

 

[linuxman]

Thanks Al, I knew I could count on you!

Thanks wescopc, I looked at the diagram, and I think I remember looking at it when you were helping jagee.

From Anole:

1). are you tracking the arc? or are you just concentrating on the elevation for South right now?

I am checking the track on the arc, and it is close but not yet perfect for USALS.

2). from what you are saying the motor latitude scale is a little off. Or maybe you've clamped the bracket too tight at the top or bottom, causing it to be elevated or depressed (?)

The motor latitude scale is off and I have been very careful to not bind it or pinch it when moving up and down.

3). it's always possible the dish's elevation (LNB location) is not perfect.
When you put the C-band LNB on there, you'll have to fight hard to keep it same as now.

Yes, that will be a challenge. That's part of the reason I wan this a close to right before I begin the experiment.

It is like having something calibrated before you begin so you have a known entity to fall back to.

Well I went out and measured this morning, and I did go the wrong way. I am still getting used to this digital level, and am still figuring out when to zero at 90 and when to zero at the horizon.

The dish is not tracking the arc as well as before I raised the motor which concerns me more than where the face of the dish is. I'll move it the other way this afternoon.

 

[Anole]

- warning -

We interrupt this discussion of antenna and motor geometry for a signal level alert! -


Popcorn brought up a good point.
Don't run your LNB signal through your motor, 'till you can be certain that the signal isn't attenuated!
edit: removed reference to C-band and Ku-band frequencies. All LNBs talk the same freq range.

We now return you to your usually scheduled geometry lesson, already in progress.

 

[Anole]

regularly scheduled . . .

Well, I could type a lot, or . . .
...refer you to the fine drawing by wescopc, above.
You might want to print it out, and then write your own numbers on it.

Also, read this discussion on Geo-Orbit. Not the links and don't do the math.
Just read through it ... several times, and let your mind absorb the concepts.

A lot of this plus or minus 90° B/S, is because we cannot measure the actual aiming direction with our levels
We measure across the front of the dish, which is perpendicular to the direction we are aiming.

The other fly in the ointment is the way the planet's geometry is laid out.
The equator being zero and the North pole being 90° creates a (90 - X) crimp in an otherwise simple concept.

The way to deal with this aiming problem is not to remember a bunch of silly rules or formula.
It's to understand the concepts, and then see if they hold when you have real numbers to work with.
It's a way to double-check yourself.
If the answer should fall in a certain general range, and it does, then it's probably right! - :up

 

[linuxman]

Well, I could type a lot, or . . .
...refer you to the fine drawing by wescopc, above.
You might want to print it out, and then write your own numbers on it.

Also, read this discussion on Geo-Orbit. Not the links and don't do the math.
Just read through it ... several times, and let your mind absorb the concepts.

A lot of this plus or minus 90° B/S, is because we cannot measure the actual aiming direction with our levels
We measure across the front of the dish, which is perpendicular to the direction we are aiming.

The other fly in the ointment is the way the planet's geometry is laid out.
The equator being zero and the North pole being 90° creates a (90 - X) crimp in an otherwise simple concept.

The way to deal with this aiming problem is not to remember a bunch of silly rules or formula.
It's to understand the concepts, and then see if they hold when you have real numbers to work with.
It's a way to double-check yourself.
If the answer should fall in a certain general range, and it does, then it's probably right! - :up

Thanks Anole!

I do understand the concepts, and have read the Geo-Orbit page at least a hundred times over the past two years. And yes Wescopc's drawing is a fine one to print out and mull over.

My problem is not the understanding of the concepts, but the use of the digital level, the math/geometry and putting it into practice. That side of my brain is what should we say, less than optimal.

I wouldn't be concerned at all now, I have great signal, but the tracking of the arc does concern me, and tells me that I don't have the "sweet spot" on the dish just right yet. Hence, the final try at it shortly.

I did read the thread about running signal through the motor, and am not doing that with the Ku signal now, and don't plan to with the C-Band signal either, provided I live long enough to actually try it. :yikes:

 

[Anole]

sources of error

Several reasons why your numbers don't seem perfect:

- the level is off (not too likely)
- the LNB has a lobe you are peaked on (?? okay , maybe)
- the LNB is not mounted exactly where it should be (very possible)

- the simple geometry on the above Geo-Orbit page doesn't put you on the arc
- you are using the "Modified Polar Mount Tracking Angles" and they're diffrent from "Declination Chart"

 

[satcom1]

EXCUSE ME!

Linuxman and Anole work on this project for 10 days and not have dish working on Clarke Belt yet?

 

[linuxman]

EXCUSE ME!

Linuxman and Anole work on this project for 10 days and not have dish working on Clarke Belt yet?

Ah! Don't pay any attention to us.

I have spent a month on a BUD fine-tuning it, but when I get done, you can call it "tuned".

Besides, it has only been 4 or 5 days now since I started last Sunday morning.

I do one thing at a time, I do it very well, then I move on.

 

[satcom1]

I guess that speaks for itself.

 

[linuxman]

I guess that speaks for itself.

Yes it does!!

 

[Anole]

your city, your bird

I needed a side view of your dish to mark up, and didn't have it.
So, I substituted another picture. Hope you can read the text over it.

edit: motor shaft angle, and related picture removed. Errors willl be corrected, and new info reposted.

Your bird is at 91° orbital, which makes it 44.9° elevation by Sat Finder 4.3
Now, we just used a satellite orbital calculator, so it's already accounted for declination in its elevation.
The dish has a documented offset of 22.6° down-look, since it's a 1.0m Channel Master offset.
see second picture
So, a vertical board placed across the rim of the dish, would be tilted back from the vertical by (44.9 - 22.6 = 22.3°)
Well, 90 - 22.3 = 67.7° on your level, referenced to zero on the ground.

edit: I took out the declination info while I think about it a bit longer...


* reference material comes from Geo-orbit page with Modified Polar Mount Tracking Angles at the bottom.

 

[linuxman]

I needed a side view of your dish to mark up, and didn't have it.
So, I substituted another picture. Hope you can read the text over it.

Given your latitude of 38.932°, your motor shaft should be at 39.56° back from vertical, which is 50.44° up from your horizontal zero reference.
see first picture

Your bird is at 91° orbital, which makes it 44.9° elevation by Sat Finder 4.3
Now, we just used a satellite orbital calculator, so it's already accounted for declination in its elevation.
The dish has a documented offset of 22.6° down-look, since it's a 1.0m Channel Master offset.
see second picture
So, a vertical board placed across the rim of the dish, would be tilted back from the vertical by (44.9 - 22.6 = 22.3°)
Well, 90 - 22.3 = 67.7° on your level, referenced to zero on the ground.

edit: I took out the declination info while I think about it a bit longer...


* reference material comes from Geo-orbit page with Modified Polar Mount Tracking Angles at the bottom.

Anole, I can't thank you enough for the drawings and the discussion we had today.

I think I can follow these simple directions and finally finish off this setup job and move on to the C-band experiment.

 

[Mr Tony]

Heck some of us take a while to perfect the dish tuning skills

And when we have a 80 signal we work on it to try and pull a 82 signal

 

[gabshere]

My problem is not the understanding of the concepts, but the use of the digital level, the math/geometry and putting it into practice. That side of my brain is what should we say, less than optimal.

again here was my problem lol my numbers never added up , i could arrange them so they would come close lol but i had to take a break and think things thru plus my dad broke his hip so had to tend to family things too...

hoping to jump back into the fire soon

great reading guys i've ordered my secret decoder ring from Sadouns and hopefully it will be here soon

 

[satcom1]

Anole-

This is a complete waste of time and resources.

 

[linuxman]

I decided to start over from scratch, partly to solve some bracketry problems I had, and partly because sometime it is easier that way.

I went out and got a 2-1/4" muffler clamp which actually is a little wider than 2-1/4 so it fits on the 2-3/8" pipe fine for the bracket to sit on when making adjustments when necessary.

I also went up to the scrap yard and got a 3/16" thick plate, 3" X 4" to slip between the U-Bolts and the holding plate to keep from distorting it when tightening.

So now, the pipe is plumb, the bracket is plumb E/W, and the bracket is plumb N/S.

Also by taking the dish off the motor, I can set the motor shaft with a closer reading using my digital level.

Here are pics of the modification.

 

[linuxman]

Well after a lot of PM's, phone calls, brainstorming, and measurements which I might add are almost impossible to do with the short motor shaft, and the little lip right up next to the motor housing, I ended up putting the motor back to 39 degrees according to the scale on the side of the motor. I did attempt to measure the motor shaft at that point and it appears that the scale puts in the adjusted latitude of 39.6 or very close to it.

I put the dish back on the motor, and it now tracks very much better than even when I first started.

I think the adjustment in the bracket and support there is as much responsible for tracking the arc better than anything else I have done.

The whole exercise was a great learning experience for me because I have a much better understanding of how the off-set dish works, and how the SG2100 works.

There is no change in the signal quality than what I reported in an earlier post. Still excellent Ku numbers for the satellites I have programmed in.

I am going to continue working on the scalar ring for the CK-1 this afternoon. The weather forecast is for clear skies and highs in the low to mid 80's all week-end, so I should be able to have a C-Band signal soon, and will find out if the CK-1 is better at C and Ku than the 621.

 

[linuxman]

Well I got C-Band!!

WooHoo!!!!

Couldn't wait to do it the right way, so I just threw it on the support arms, measured the focal distance which by the way, I was incorrect the other day, the focal distance is 28.5 inches and taped it together.

It isn't centered as you can see in the picture, it is pretty close with up and down, but left and right it is off.

Still have ku 12060 V test cards at 45% SQ and as you can see 3720 H C-Band at 29% SQ. I will blind scan shortly just to see what else it will bring in.

In the mean time, some of you give me some ideas of how to secure the scaler ring. Please!! While you are thinking, the arms are 3/4 inch OD. The shiny things are 3/4" set screw couplers, that idea didn't work out so good. See what you can come up with to help me out here.

I would like to secure the scaler, fine tune it a little, and finish this experiment this weekend.

 

[Lak7]

I don't know if this matters, on my BUD I have my BSC621 rotated 90cw to what you have.