One Meter Primestar Mini-Bud Experiment

[voomvoom]

But as I was telling Al earlier, at one time I had both C and Ku pretty darn good on the Birdview Perforated dish. The only reason is because of the outstanding surface reflectivity of the Birdview dishes.

Yes, and I wasn't thinking about the different wavelengths as satcom1 mentioned (although I know I knew that, can't remember anything much anymore?). It could be that on that Birdview the 2 different wavelengths happen to hit the right spot together? There will be places they will hit together, or close enough to be the same spot.... but it might not hit that spot on the P* together...?? Then again..... it might..!!! So let's go for it...!!!!!

 

[voomvoom]

Why not loan one to Linuxman? He'll play with it like nobody I know.
And if it'll improve performance, he'll demonstrate it.
Save you a lot of experimenting.

Not a bad idea, but I wanted two of them, then I would be short one.
I totally agree with the rest, he would play it to the utmost, and demonstrate it's performance, and most likely save me a lot of time.....?

 

[linuxman]

I had forgotten how much "fun" it is to tune in a motorized Ku dish.

But I got it roughed in with good Ku signal quality from AMC6 72W to G27 129W and all in between using USALS only.

But now it's time to do some serious tuning. I started with my FS IR-5400NA because that was the receiver controlling the motorized 84e, and already had satellites and channels scanned in and USALS setup.

I am going to switch over to my Pansat 2500a, but will have to do a factory reset to get USALS back. It is currently set up for BUD tuning.

I'll run me a piece of coax from the dish to the front porch, and set it up to blind scan a few satellites this evening from the shade, and the fact that it will take 20 minutes per satellite to do it.

Should have the Ku fine-tuning done by tomorrow morning. Got to run to Lowes and Skywalker to get some "adapter" goodies to make the scaler ring fit snugly in preparation for the C-Band stuff.

 

[linuxman]

Got the Pansat 2500a reset last evening and scanned in a few satellites.

Started the fine-tune of the dish today, and I have some questions for all the math gurus out there.

I have pretty decent Ku signals from 72W to 129W, but they are not outstanding by any means. Hence the questions.

My Latitude is 38.9 rounded off, so I have the motor setting at 39 degrees by the book.

My total elevation for my latitude and longitude is is 45 degrees. Latitude 38.9, and longitude of 90.7.

If I understand that correctly with a 22 degree off-set dish, the face of the dish should be at 23 degrees, or if subtracted off of the 90 degree mast, it should be 77 degrees. Is that correct?

In the pictures below, the one with the white lines in it are the questions I have.



My digital level shows the motor arm at 72.5 degrees off the 90 degree mast, or 27.5 degrees off ground level. What angle should that be?

My digital level also shows the center of the face of the dish to be at 71.5 degrees off the 90 degree mast, or 28.5 degrees off ground level.

I am thinking I have gotten the signals I currently have off just part of the dish. It appears that I am about 5 degrees off and should adjust to a higher point on the dish to see if the signal pops in again. I had this happen once before when setting up a multi-LNBF dish.

The remaining question is how in the heck have I gotten the pretty decent signals I have all the way across the arc with it being off like that?

I'm talking 90% SQ on 72W 12053 V, 75% SQ on 12060 V on 91W, and 75% SQ on 129W White Springs.

They aren't bad numbers, but if I hope to get some C-Band, I have to be sure they are the best I can get.

 

[linuxman]

I think I found the answer here.

Like most of these explanations, I had to read it a few times to let it sink in.

Here is part of what they had to say:

The 22 degree offset means that the beam comes off the dish at an offset angle of 22 deg. With the feed at the lower edge, this means that the beam comes off the dish at a 22 deg angle upwards. So if the dish reflector itself is vertical, the beam elevation angle is 22 deg.

For elevation angles lower than 22 deg the dish must be tilted forwards and downwards. For very low elevation angles the lower edge of the dish and the back end of the feed support arm may meet up with the mount pole. In such cases it is necessary to mount the dish upside down with the feed at the top. This way you can go down to zero elevation angle - which is applicable if you want to use the dish for terrestrial purposes.

For elevation angles higher than 22 deg you need to tilt the top edge of the dish backwards. A backward tilt of 68 deg would mean the elevation angle was 90 deg, with the beam going straight upwards.

So I need to tilt my dish down another 5 or so degrees which should be where I get the best signal.

I also think that because the motor elevation is set correctly, that allowed me to get signals across the arc just fine.

After supper I will hook up again and make the adjustment. More on the results later.

 

[gremlin411]

I was with you all way until you got to the part about subtracting off the 90 deg mast.

 

[linuxman]

I was with you all way until you got to the part about subtracting off the 90 deg mast.

You get confused? I'm the one that is confused.

Went back out after eating, hooked up, and same reading on G11. Loosened the bolts, and cranked the dish until the digital level read 80 degrees. Slowly started bring the dish to 77 degrees and no signal went a little higher to 75 degrees still no signal. Slowly cranked it to 70.5 degrees and that's where it all came in.

I have no explanation, and still don't understand the degree numbers, but I ain't going to argue with my Signal Quality now.

Here are the Ku numbers:

129W G27 11964 H is bouncing between 80 - 85% SQ
127W G18 11720 V is rock solid 60% SQ (I think the numbers there have decreased in recent weeks)
101W AMC4 11860 H is rock solid 75% SQ and 11916 H is 99% SQ
91W G17 12060 V is rock solid 90% SQ
87W AMC3 11716 H is a solid 90% SQ
74W H2 11734 H is a solid 75% SQ was at 90% earlier today
72W AMC6 12053 V is a rock solid 90% SQ

I have quit tuning with the OEM Primestar LNBf. Tomorrow I will start fitting the CK-1 onto the support arms.

Surely I will be able to get some C-Band signals of some kind with Ku numbers like this.

I would still like to have someone explain the degree numbers to me and why mine appear to be off?

If you can draw diagrams or whatever it takes for my thick non-mathematical mind can understand it, I would certainly appreciate it.

 

[Anole]

Okay, I may have to re-edit this a few times to get it right and get in all I want to say. . . .

First, on some of the confusion, let's refer to your picture with the white lines:
1). The long line to the left, along the face of the dish is A or left-line.
2). the short line to the right, along the motor's dog-leg, is B or right-line.

3). Line A is not the elevation of the dish.
The dish is actually aimed up and to the left about 45° in that picture.
Since the dish looks up about 22° from where it seems to be pointed...
... Line A is not even perpendicular to the aim-line.

4). If you put a board across the dish at A...
- set your level so the horizon is zero
- then measured the tilt-back of the board...
- and added your 22° to it, ...
- you'd have the direction (elevation) the dish is actually aimed at.
And for you, apparently, somewhere around 45° is correct for your True South bird.
All you have to be sure of, is that the 22° is correct , and with a level and a board, you can ignore everything else in the system, and set your elevation! -
This assumes your Ku-LNB is in the saddle like it's supposed to be.

Not sure that helps, but I felt it needed to be said.
I doubt there's really anything contained above that you hadn't already thought of...


Now, on to the white line B... That's another confusing thing.

It's an artificial bend in the motor shaft, to allow the dish to be set closer to the motor.
And to compensate for the roughly 30° it dials in, you compensate by dialing out the same number of degrees on your the dish mount.
By "dish mount" , I mean the elevation mount on the back of the dish that clamps to the motors shaft.

(Now, be advised that different motors use different angles on the shaft.
I believe that early 2100's and late 2100's have different angles, too! )

The actual angle of the motor's shaft (up above the dog-leg) is supposed to be such that the upper shaft is parallel to the earths "shaft".
If you think about it, this should not even include any declination.
The actual declination is applied using the dish's elevation adjustment, to get your 5x or whatever down-tilt required to see the Clarke belt.

The whole matter is complicated and confused (obfuscated) by the downward angle of the dog leg, and the upward look-angle of the dish.
These two numbers are not the same, else the whole exercise would be a breeze! -
The motor depresses the dish's elevation by 30°, and the dish actually looks 22° higher than it appears .
No wonder people freak out adding and subtracting the numbers to get it right! -


One last thing. That dish you show in your picture is a Channel Master / Andrew.
It has the three LNB support arms.
I am no expert on Primestar dishes, but I think they bought them from two companies.
The other company used the single stiff LNB support attached to the bottom of the dish.
Maybe I'm wrong and the 3-arm was only on larger dishes, but we'll leave that to the experts to argue.

So, be sure you look up the exact specs on your size and brand dish, and know the actual offset angle -

Next, look up your motor, and find the correct dog-leg angle (or measure it), so you know exactly what you've got. -

This will clear a bit of the confusion when you fire up the calculator and numbers are close but not exact.


Hope the above adds clarity and not confusion.
Let me know, and I'll just delete the post if necessary.

 

[linuxman]

Crap!!!

Don't delete it, I need to read it a few more times first.

Maybe I should copy and paste it into a document right now before it is gone.

It's late, and I just read it, will re-read it in the morning a few times, and digest. I may have more questions.

Thanks!!!

 

[linuxman]

4). If you put a board across the dish at A...
- set your level so the horizon is zero
- then measured the tilt-back of the board...
- and added your 22° to it, ...
- you'd have the direction (elevation) the dish is actually aimed at.
And for you, apparently, somewhere around 45° is correct for your True South bird.
All you have to be sure of, is that the 22° is correct , and with a level and a board, you can ignore everything else in the system, and set your elevation! -
This assumes your Ku-LNB is in the saddle like it's supposed to be.

Okay, I set the level at zero for parallel with the mast which is 90 degrees. The horizon is zero on the level when first turned on.

Put a board across the dish from top to bottom and set the level on it. The reading was at 20 degrees. So if I add 22 degrees to that, I am pointing at 42 degrees.

I don't have the specs on the off-set of the dish, and I am using an upside down bracket from a 75e and home-made brackets to attach it to the motor so the off-set could very well be 25 degrees instead of 22.

So, be sure you look up the exact specs on your size and brand dish, and know the actual offset angle -

Next, look up your motor, and find the correct dog-leg angle (or measure it), so you know exactly what you've got.

I don't have the specs on this dish, and can't seem to find them any more. There is a link on google that pointed to spec sheets on the Andrews website, but that link is now dead.

My motor is an older SG2100. I bought it in December of 2006 and it seems to be correct.

I am not sure which part of the "dog leg" I should measure if possible with dish on it.

Thanks for the help, and no I didn't think about zeroing out the level at a different position to make things easier to understand.

All of this has been very instructive and perhaps someone with knowledge of the angles of the SG2100, and someone who may have specs on the dish.

My dish doesn't say Channel Master on the back, but it is:
Part# 3040642-02
Mold# 1.0M-1

Thanks!!

 

[Anole]

Put a board across the dish from top to bottom and set the level on it. The reading was at 20 degrees. So if I add 22 degrees to that, I am pointing at 42 degrees.

I don't have the specs on the off-set of the dish, and I am using an upside down bracket from a 75e and home-made brackets to attach it to the motor so the off-set could very well be 25 degrees instead of 22.

Is 42° correct for you? Because it'd better be!
The offset of the dish is the offset of the dish.
Nothing in the bracketry can change nor influence that.

All you have to be sure of, is that the 22° is correct , and with a level and a board, you can ignore everything else in the system, and set your elevation! -

The upside down bracket has nothing to do with the dish's offset.

I am not sure which part of the "dog leg" I should measure if possible with dish on it.

Above the bend in the shaft.
The actual output of the motor is parallel to the earth's core.
Luckily, the settings on the side of the motor bracket should get you set correctly.

 

[linuxman]

Is 42° correct for you? Because it'd better be!

42 degrees is not correct, it should be at 45 degrees.

The offset of the dish is the offset of the dish.
Nothing in the bracketry can change nor influence that.

The upside down bracket has nothing to do with the dish's offset.

Great, understood!!

Above the bend in the shaft.
The actual output of the motor is parallel to the earth's core.
Luckily, the settings on the side of the motor bracket should get you set correctly.

I have measured the angles on the motor and it's output shaft and they are on the picture.

Sorry if I don't know all the terms, but I don't understand "parallel to the earth's core"?
It measures 43 degrees with zero at the horizon. If that means this measurement is supposed to be at 45, that might be the problem. The motor might be off by two degrees.

As you can see in the picture the motor is set at 39 degrees which is my latitude. (38.9)

The other angle on the motor is 17.5 degrees with zero at the 90 degree mark. May have no bearing on the discussion.

Here is the marked up picture:

 

[linuxman]

Well without and explanation of "parallel to the earth's core", I did a little research. I think what Anole is referring to is the latitude, so the angle above the bend on the motor should be equal to your latitude, but I found an explanation and got some ideas from Satsig's SG2100 Polar Mount Setup Page.

This is an example for my location with latitude 38.932 and longitude of 90.747.

I got the results from the polar mount satellite dish pointing calculator at satsig.net, which I have used many times for C-Band and didn't think it had a bearing on off-set dishes.

The MAIN MOTOR AXIS angle must be 39.63 degrees.

The SMALL DOWNWARD TILT ANGLE of the dish must be - 5.44 degrees.

And according to Eric Johnson at the site and this is his wording using my numbers and comments which are in parentheses:

First set the scale on the fixed bracket on the SG-2100 polar mount motor bracket. Do this calculation X = 90 - 39.63 so X = 50.37 so set the scale on the fixed bracket to 50.37 (the scale is off on my SG2100 as I discovered today, so set the scale wherever it falls using a digital level to find the angle)

Now work on the scale on the back of the dish. Do this calculation Y = 40 - 5.44 so Y = 34.56 deg. so set the scale on the dish to 34.56 deg
X is not the real beam elevation angle but a larger angle which needs reducing a bit by the small downward tilt of the dish, in order to see a satellite due south of you.
The scale on the dish is intended for use when the dish is attached to a vertical pole. In this case the 'vertical' pole has been bent down by exactly 40 degrees so the dish scale is wrong by 40 deg.

Elevation angle of the beam = 180 - 90 - MAIN - TILT = 180 - 90 - 39.63 - 5.44 = 44.93 deg for a due south satellite

90 - 39.63 = 44.93 degrees

Real elevation angle of the beam = 50.37 - 5.44 = 44.93 deg (for a due south satellite)

I never could figure out what the 40 degree bend was taken from.

Maybe someone can figure out where he got that figure and what it is taken from.

Here is my marked up picture:



I took a more accurate reading from the output shaft on my motor and it is 42.5 degrees angle and according to the above it should be 39.63 degrees, so I will need to adjust the motor accordingly.

That is what accounts for the almost 3 degrees my dish face if off by right now.

The offset angle of the dish I got today from ASC Signal Corporation who ended up with Andrew Dishes.

The offset angle is 22.6 degrees, so that accounts for the other half of a degree.

That motor is where I set it a year and a half ago and never knew any difference. I don't see how it worked so well before, and how it is doing so well right now, but it is.

If it cools down a little this evening, I will make the corrections.

 

[Anole]

Okay, I haven't read your reference material yet, but I will.

Hope these comments will help a bit:

Sorry for the "earths core" crack.
I meant the earths shaft or the imaginary line from North to South pole, about which the planet rotates.
Your motor shaft should be parallel to that, I believe.
If it is, a dish mounted perpendicular to that shaft, will point out in space above the Clarke Belt.
Then, you apply declination, to look down at the Clarke Belt where the satellites are.

All the calculator programs will have the look-down or declination built in to them.
So, if your calculator calls for (roughly) 45° elevation but says there's 5° declination, then your motor shaft should have 50° of tilt-back from a plumb line (tilt back to the north for the top of your motor shaft).
And your dish should then have the 5° of declination dialed in.
This should put you right on target for your True South satellite.

Sound right so far?



PS: For those who've noticed occasional mistakes like "5x" in a post above, what I do it type an "x" instead of an "°", then go back and paste in the "°" character.
You find it using the Windows utility program called Character Map.
From your desktop, it's found at:
START | All Programs | Accessories | System Tools | Character Map

 

[linuxman]

Okay, I haven't read your reference material yet, but I will.

Hope these comments will help a bit:

Sorry for the "earths core" crack.
I meant the earths shaft or the imaginary line from North to South pole, about which the planet rotates.
Your motor shaft should be parallel to that, I believe.
If it is, a dish mounted perpendicular to that shaft, will point out in space above the Clarke Belt.
Then, you apply declination, to look down at the Clarke Belt where the satellites are.

All the calculator programs will have the look-down or declination built in to them.
So, if your calculator calls for (roughly) 45° elevation but says there's 5° declination, then your motor shaft should have 50° of tilt-back from a plumb line (tilt back to the north for the top of your motor shaft).
And your dish should then have the 5° of declination dialed in.
This should put you right on target for your True South satellite.

Sound right so far?

Hey Anole!

Well I followed the instructions from my post above and set the motor shaft at 39.6 degrees which in fact when I zero the level at 90 degrees, does show exactly 50 degrees. So I would say that you and the other guy are saying the same thing, just coming at it from different places.

PS: For those who've noticed occasional mistakes like "5x" in a post above, what I do it type an "x" instead of an "°", then go back and paste in the "°" character.
You find it using the Windows utility program called Character Map.
From your desktop, it's found at:
START | All Programs | Accessories | System Tools | Character Map

I wondered where you were getting those.

Back to the subject.

After doing all the changes, the front of the dish still shows 20 degrees of elevation.

With the 22.6 degree offset of the dish, and 20 degrees on the face, that is 42.6 degrees total elevation.

It is supposed to be 44.93, so I am still 2 degrees and some change off.

I didn't gain any thing as far as SQ, but then I didn't lose anything either.

I am a little frustrated at going the extra mile and not gain anything on the face of the dish or SQ either.

Maybe it is time to move forward with the real experiment of trying to get a C-Band signal on this dish and quit trying to pick the Ku to death.

What do you think, should I move on, or try and figure this out?

 

[qwert1515]

Another way to get the "degree" (°) symbol is to hold down the "ALT" key and type "0176".

Also I don't think you need to be perfect on the Ku band to get C-Band. (C-Band might require you to increase the dishes elevation a little bit)

 

[linuxman]

Another way to get the "degree" (°) symbol is to hold down the "ALT" key and type "0176".

Also I don't think you need to be perfect on the Ku band to get C-Band. (C-Band might require you to increase the dishes elevation a little bit)

Thanks Qwert!!

For both suggestions.

 

[Anole]

Thanks, Qwert, but I can never remember what the code number is.

Back to the subject.

After doing all the changes, the front of the dish still shows 20 degrees of elevation.

With the 22.6 degree offset of the dish, and 20 degrees on the face, that is 42.6 degrees total elevation.

It is supposed to be 44.93, so I am still 2 degrees and some change off.

I didn't gain any thing as far as SQ, but then I didn't lose anything either.

I am a little frustrated at going the extra mile and not gain anything on the face of the dish or SQ either.

Maybe it is time to move forward with the real experiment of trying to get a C-Band signal on this dish and quit trying to pick the Ku to death.

What do you think, should I move on, or try and figure this out?

I'm confused.
What did you do? Did you change the motor-to-post angle or just document & understand it?
Why didn't you raise the dish's elevation (where it clamps to the motor), so the face of the dish agrees with your prediction?

And his 40° angle is the motor's dog-leg... On some motors, it' s 30°, or 40°, or whatever.
Sadoun used to have a list on his site showing what various motors were, but I was unable to find that info when I looked this morning .

Sounds to me like you've almost achieved full understanding (at which point, I'll feel like I have, too).
We've discussed that there may be more than one hot spot on the LNB when waiving it around vertically (in elevation).
So, why not go that short mile and swing the dish by the dish-to-motor elevation adjuster, up 'n down 5° in 1° increments, and see what gives on Ku.
Or, just swing it slowly, while monitoring Quality, and see if there are several peaks?

 

[linuxman]

Thanks, Qwert, but I can never remember what the code number is.

I'm confused.
What did you do? Did you change the motor-to-post angle or just document & understand it?

I changed the motor latitude adjustment on the side raising the motor/dish up until I got 39.6 degrees on the motor shaft. The little pointer on the latitude side of the motor now shows 38 degrees whereas it was at 39.

Why didn't you raise the dish's elevation (where it clamps to the motor), so the face of the dish agrees with your prediction?

I did but got no signal, so I lowered the dish until I got signal and even 5 degrees below that. Secondly, I adjusted the dish up another 10 degrees hunting for a second signal spot, but found none.

And his 40° angle is the motor's dog-leg... On some motors, it' s 30°, or 40°, or whatever.
Sadoun used to have a list on his site showing what various motors were, but I was unable to find that info when I looked this morning .

Sounds to me like you've almost achieved full understanding (at which point, I'll feel like I have, too).

Yes, I think I might have a real grasp of how the motor works on the off-set dish. I very much appreciate your help in my understanding.

We've discussed that there may be more than one hot spot on the LNB when waiving it around vertically (in elevation).
So, why not go that short mile and swing the dish by the dish-to-motor elevation adjuster, up 'n down 5° in 1° increments, and see what gives on Ku.
Or, just swing it slowly, while monitoring Quality, and see if there are several peaks?

Already answered above, but I did try unsuccessfully to find other signal spots, but there were none.

Tomorrow afternoon, rain permitting, I will start fitting the scaler ring to the support arms. With no unforeseen disasters, I will be able to test for the first C-Band signal by dark.

I don't believe in luck. I believe in adequate or inadequate preparation.

EDIT: You know, I just thought of something. I think I took the measurement for the 39.6 incorrectly. I should have had the level zeroed at 90 for that reading. The movement of the side guage made me think of that. I went from 39 to 38 in effect raising the motor but having to lower the dish.

I should have gone from 39 to 40, lowering the motor, and then have to raise the dish.

Well, !#$%$!%!^!

Tell me I am wrong. Please!

 

[voomvoom]

You know, I just thought of something. I think I took the measurement for the 39.6 incorrectly. I should have had the level zeroed at 90 for that reading. The movement of the side guage made me think of that. I went from 39 to 38 in effect raising the motor but having to lower the dish.

I should have gone from 39 to 40, lowering the motor, and then have to raise the dish.

Well, !#$%$!%!^!

Tell me I am wrong. Please!

Will it make you fell better if I do?

OK You're Wrong..!!!