How do you measure a Ku motor to see if it's level?

[rogerduncan100]

Thank you AcWxRadar for your excellent explanation of how to get a motorized dish to exactly follow the arc (in Dee Ann's new thread). I think to make this happen you not only have to have the mounting post perfectly plum but you have to have the motor exactly level. Right now my setup is totally out to lunch on 30W because it isn't level enough, I think.

How do you measure a Ku motor to see if it's level?

I have an SG2100 motor and it's a wonderful collection of curves, not a straight edge on it! Besides, what really matters is that the shaft is aligned right but how can you know and how can you measure? The shaft is not only on an angle to the ground, it's bent!

Checking the mounting post for plum is easy. Just lay a level on it at two locations ninety degrees from each other. Checking a motor for level is another matter. Any ideas?

 

[rogerduncan100]

A copy of Radar's explanation of how to get a dish to follow the arc:

Hi Dee,

Regarding the degree that the "dish" has to tilt, depending upon what you are referrig to, this should be automatically compensated for by the rotation of the motor axis and calibrated by you by setting the motor angle to match your geographic latitude angle (in combination with your USALS settings for your lat and long coordinates withing your reciever menu).

Truly, it is so very simple that most don't get it. Everyone seems to think that there is much more to it and there just isn't.

1] Start with a plumb mast that is sturdy.

2] Get a rough idea of your true south direction to start to aim.

3] Set your motor latitude to your site's latitude.

4] Set your dish reflector angle to compensate for the motor tube bend angle and your site lattitude (find this information in the tables of the motor manual/dish installation manual).

5] Set your receiver to a known, active an hot TP nearest your due south direction.

6] monitor the signal/quality meter on your receiver while you pan your dish back and forth (East to West) in a short arc where you expect the satellite to be.

7] Be paitient. Move the dish a very small amount, then back off and wait so that that your receiver has plenty of time to lock on to a signal if it finds one. Have a TV and receiver out at the dish site so that you can get immediate feedback from your adjustments. Keep in mind that some receievers are not very quick to respond, so you have to be patient and take your sweet time.

8] Once you get a signal to come in, peak it kust enough so that you can test it and verify it. Scan the signal and compare your scan results with "The List", Lyngsat or other source to be sure that you are on the proper satellite.

9] If you are on the proper satellite, the one you were aiming and intending to dial in, then peak the signal. and tighten the bolts just enough to keep the dish from moving on you. Do NOT overtighten.

10] Bump the sat dish to the next sat to the east or west using the motors USALS control and go to the furthest satellite in either direction that you can still maintain a signal from.

11] Monitor the signal quality while you gently push and pull on the dish from the backside. Note which direction you have to go to improve the signal.

12] Command the dish to go back to ZERO or HOME.

13] Readjust the dish elevation or the motor azimuth to match what you found instep 11 and then return the dish to the same sat and check your adjustment results.

NOTE: What I am saying here is to try to make your adjustments at your home position (dead center)and not while the dish is pointed to the far east or far west. You will fight gravity in those positions and that can twist your dish brackets when you loosen your mounting bolts and it becomes a never ending loop to get it set properly.

14] Before making any adjustments, check the furthest sat to the west that you can maintain a signal from and the furthest sat to the east that you can maintain a signal from. Note your error and the direction, then return to the motor's HOME position and make that adjustment there. Then verify if your adjustment was proper.

15] If you have improved your signal and it is really looking swell so far, go outward with your motor to the next furthest satellite on both the east and west side agian and that you can still retain a signal from and repeat the process over again. You will eventually make your way across the entire arc and fine tune your dish tracking.

NOTE: This is a slow "calibration" process. You do not want to PEAK your signal at each step, just improve it a little from the last step. It is like Bob Ross' "The Joy of Painting". You don't go fast and sloppy, you go slow and methodically. Here you just want to improve your signal slightly, then return to check the opposite side of the arc and improve it slightly. Don't go to extremes, just rock it back and forth and improve your signal on each side a little at a time. Everyone has their own method, figure out what feels best for you and if it works, stick with it. You can refine it as you go.

NOTE: Trust me when I say that you should not go fast. If you go too fast, you will tend to cut corners and try to peak the signal too much at each sat position. That is not what you want to do. You need to go back and forth between west, center, east, center and west and back and make minor adjustments at each stop and then go further east and west as you are able.

NOTE: It will be very beneficial to you if you can enter one strong transponder on each satellite and nothing else (don't even scan for channels). There is a very good reason for doing this, I will explain shortly.

Most satellite receivers will default to monitor at the first satellite in the list, not te first active TP.
Therefore, you might be panning for a TP that isn't broadcasting anything and it will be very ellusive. If you create an aligment list, it will save you a great deal of time. With an alignment list, the only TPs in the list are always active, so it doesn't matter how you open the sat list for monitoring since every TP is "HOT" ot broadcasting 24/7 amd therefore you can align your dish anytime of the day.

I hope you are following my way of thinking. I have found that it makes life so much easier to do it this way. If you follow my method, it takes about 5 to 15 minutes to get the job done with perfection.

If you need more info on this subject, you can PM me and I will gladly help.

RADAR

How can I be sure my motor is level? Any ideas, guys?

Roger

 

[adrian]

Motor level

Mate that is a sound explanation.
In my post of yesterday i enquired about the formula to calculate the arm angle of a sat motor (at 0) at any given latitude.Surely that is the most practical route by placing a digital inclinometer against the motor arm at 0.Once you set your arm thats it.

 

[Mikey11]

i normally put a small level across the top of the motors bracket....straight across back near the post....then straight across out near the motor....then corner to corner in both ways....all 4 readings should be 100% level....remember, just because your post is level does NOT mean the motor will be!!....sometimes the motor brackets bend or twist from over tightening the bolts!!

 

[Tron]

That is a good point. You need to start off with a level pole, but the part that really needs to be level is the bracket. If the bracket is level, the motor should be level as well.

 

[B.J.]

The method I have used quite sucessfully of late, is to forget about using the scale on the motor, and forget about trying to find some flat surface on the motor to use an inclinometer on, and, as hinted at in the post by Adrian above, ie before the dish goes on, put the inclinometer on the bent motor shaft, and in some cases even with the dish on there, you can find a surface parallel to this bent shaft. But the question then, is what angle are you looking for there.

This angle should be the motor elevation MINUS the angle of the bend in the shaft. However, unlike Radar, and others here, I don't use 90-latitude for the elevation, since this will by definition make your tracking off by up to 0.6 degrees. Instead, I use the modified declination method, which in most cases uses a latitude that's ~ 0.5-0.7 deg higher than your latitude. You can use 0.6, or you can use the calculator at BJDISCALC2 to figure out the adjusted latitude setting.

For example, in my case, my latitude is 44.1 . Using the calculator, I determine that the latitude I should use is 44.8, ie ~ 0.7 degrees greater than my actual latitude.

The motor elevation is 90 MINUS this value, ie 90-44.8=45.2 ,

Now, I subtract the motor shaft bend angle from this. In my case, my SG2100 has a 30 degree bend, so 45.2 - 30 = 15.2 .

I put my digital level on the bent shaft, adjust it so it reads 15.2, and the motor elevation is set. At that point, all I need to do is find my true south sat, adjust the DISH elevation and motor azimuth (rotate entire mount on pole) to peak that sat, and the alignment is pretty much complete. It might be necessary to tweak the azimuth on an extrem sat, but that's often not necessary.

I've used this method nearly a half dozen times over the past few weeks when I moved my 90CM Fortec/SG2100, then took the dish down to repair the motor a few times, then took it down again to switch to a new (defective) SG2100. In each case I had to start from scratch with the motor elevation, and the digital level on the bent motor shaft worked well in each case.

 

[Mikey11]

The method I have used quite sucessfully of late, is to forget about using the scale on the motor, and forget about trying to find some flat surface on the motor to use an inclinometer on, and, as hinted at in the post by Adrian above, ie before the dish goes on, put the inclinometer on the bent motor shaft, and in some cases even with the dish on there, you can find a surface parallel to this bent shaft. But the question then, is what angle are you looking for there.

This angle should be the motor elevation MINUS the angle of the bend in the shaft. However, unlike Radar, and others here, I don't use 90-latitude for the elevation, since this will by definition make your tracking off by up to 0.6 degrees. Instead, I use the modified declination method, which in most cases uses a latitude that's ~ 0.5-0.7 deg higher than your latitude. You can use 0.6, or you can use the calculator at BJDISCALC2 to figure out the adjusted latitude setting.

For example, in my case, my latitude is 44.1 . Using the calculator, I determine that the latitude I should use is 44.8, ie ~ 0.7 degrees greater than my actual latitude.

The motor elevation is 90 MINUS this value, ie 90-44.8=45.2 ,

Now, I subtract the motor shaft bend angle from this. In my case, my SG2100 has a 30 degree bend, so 45.2 - 30 = 15.2 .

I put my digital level on the bent shaft, adjust it so it reads 15.2, and the motor elevation is set. At that point, all I need to do is find my true south sat, adjust the DISH elevation and motor azimuth (rotate entire mount on pole) to peak that sat, and the alignment is pretty much complete. It might be necessary to tweak the azimuth on an extrem sat, but that's often not necessary.

I've used this method nearly a half dozen times over the past few weeks when I moved my 90CM Fortec/SG2100, then took the dish down to repair the motor a few times, then took it down again to switch to a new (defective) SG2100. In each case I had to start from scratch with the motor elevation, and the digital level on the bent motor shaft worked well in each case.

this sounds good but its not really answering the original question....

how to make sure the motor is level....

 

[B.J.]

this sounds good but its not really answering the original question....

how to make sure the motor is level....

Perhaps not, but it's answering what I thought it was really asking. If the question is literally how to make sure it's level, then the answer is that you don't WANT it level. What I described gets the motor at the proper orientation in the north/south plane. Yes, you also need it to be vertical (or the top level) in the east/west plane as well, but there is no way to adjust that other than bending your pole, and I really doubt that any motor will be out in that direction anyway. If it is, you should send it back for a refund.

 

[AcWxRadar]

Excellent information from Mikey, Tron and B.J.!

You don't want the motor tube to be level, of course - as B.J. indicated. But you do want the motor bracket to be square and level. If your mast is level, the bracket should be level, too. Unless it has been deformed.

One word of caution. If you take a level and check the motor bracket itself for plumbness, make sure that you check it with the motor bolted into the bracket (otherwise the sides of the bracket may tend to flare out a little and you won't get a true reading).

If you find that your bracket has been bent or deformed because it was overtightened at some time, don't use it! Get another bracket and start with one that is perfectly square. I know that you can purchase new brackets and hardware for some motor models at Sadouns.

I check the bracket itself with the level placed across the top or the bottom of the edges of the side brackets (whichever way you can get around the motor), then I also check the outside walls of the bracket for vertical. I also like to check the back of the bracket itself, but this isn't quite as easy to do since the mounting bolts are in the way. I have used a small piece of straight steel stock to kinda make an extension for the level to rest on and then slip the steel stock in between the mounting bolts and against the back of the bracket. This is where you will most likely notice if the backet has been deformed by overtightening.

The other point that I check (with an inclinometer) is the bottom or the belly of the motor. Without the dish installed on the motor, I read the angle on the inclinometer. Subtract this reading from 90 and the result should be equal to the degree shown on the motor brackets latitude scale. I do this mostly to verify the accuracy of the motors latitude scale or to create a new scale if the original scale is illegible.

RADAR

 

[rogerduncan100]

Thanks for the great information!

I had a pleasurable afternoon modelling the earth and the geostationary satellites using my wife's large exercise ball, string, tape, lego etc..

I discovered that the declination angle for my true south is 0.3 degrees higher than for the extreme satellites at 30W and 125W. That explains the rationale behind the method B.J. uses, where the motor's elevation angle is raised more than half a degree. B.J.'s setup will split the difference and get the motorized dish following the arc as close as is possible.

The SG2100's 30 degree bend is itself a compromise. I think the only way to get a motorized dish to follow the arc perfectly is to set it up with the exact right bend for the latitude.

Roger

 

[adrian]

Motor level

I am of the opinion that the motor will be level if one use ones latitude incorporated into a formula allowing for the angle of the motor arm bend,being 30,40 or whatever.The resulting answer will give you what the arm angle will be (with the motor at 0)which is then set by way of a digital inclinomitor.The assumption of course is that the mounting pole is dead 90 degrees.
To make strengthen the mounting of my motor i have replaced the U bolt with two straight bolts and two brackets at the back, placed in front of the grove on the back plate of the motor.Surely a mathematician can come up with such formula.

 

[B.J.]

.....

One word of caution. If you take a level and check the motor bracket itself for plumbness, make sure that you check it with the motor bolted into the bracket (otherwise the sides of the bracket may tend to flare out a little and you won't get a true reading).

If you find that your bracket has been bent or deformed because it was overtightened at some time, don't use it! Get another bracket and start with one that is perfectly square. I know that you can purchase new brackets and hardware for some motor models at Sadouns.

I check the bracket itself with the level placed across the top or the bottom of the edges of the side brackets (whichever way you can get around the motor), then I also check the outside walls of the bracket for vertical. I also like to check the back of the bracket itself, but this isn't quite as easy to do since the mounting bolts are in the way. I have used a small piece of straight steel stock to kinda make an extension for the level to rest on and then slip the steel stock in between the mounting bolts and against the back of the bracket. This is where you will most likely notice if the backet has been deformed by overtightening.

The other point that I check (with an inclinometer) is the bottom or the belly of the motor. Without the dish installed on the motor, I read the angle on the inclinometer. Subtract this reading from 90 and the result should be equal to the degree shown on the motor brackets latitude scale. I do this mostly to verify the accuracy of the motors latitude scale or to create a new scale if the original scale is illegible.

RADAR

This refreshes my annoyance with the NEW SG2100 that I just bought, compared with my OLD SG2100. With my OLD SG2100, the bracket is a very solid piece of metal, and all the surfaces were square. On several occasions, when I had the motor in the house, I just set the motor on a level table, setting it on it's bracket, and used the angle of the bent shaft method to adjust the motor elevation while the motor was still in the house, then took the thing outside, put it on the pole, put the dish on it, and after finding my true south sat via dish elevation, I was tracking the whole arc without touching the motor elevation. With that %$$*%* "NEW" SG2100, there isn't a flat surface anywhere, either on that motor or on the darn bracket. The bracket wouldn't even sit flat on my table, it rocked from side to side. I had to do the elevation adjustment after it had been installed on the pole, which would have been easy, except that I put the dish on first (mistake). Also, that bracket on the NEW SG2100 is a different design, ie the holes on the motor are in different places, and the indicator is different (on motor vs washer), and the new bracket covers up the one potentially flat surface on the motor.

Thanks for the great information!

I had a pleasurable afternoon modelling the earth and the geostationary satellites using my wife's large exercise ball, string, tape, lego etc..

I discovered that the declination angle for my true south is 0.3 degrees higher than for the extreme satellites at 30W and 125W. That explains the rationale behind the method B.J. uses, where the motor's elevation angle is raised more than half a degree. B.J.'s setup will split the difference and get the motorized dish following the arc as close as is possible.

The SG2100's 30 degree bend is itself a compromise. I think the only way to get a motorized dish to follow the arc perfectly is to set it up with the exact right bend for the latitude.

Roger

I must admit that I'm a bit embarrassed, in that when I read your post, I thought that surely it must be more than the 0.3 degrees difference you mention, but I checked one of my own programs, and it looks like if anything, it's LESS, even closer to 0.2 deg. So I'm going to have to eat my words a bit, words that I've been saying for 2 decades on the web.

Probably will confuse things even more, but I've had a little VB program on the web for years at http://www.eskerridge.com/bj/sat/satview.exe (unfortunately this program requires the VBRUN.300 dll to run. Some will have this already, but if not google for it, and dozens of download sites will pop up, including VB3Run.exe Run-Time .dll for Visual Basic 3.0 Apps .

But anyway, the modified declination method for alignment is based on a 0.5-0.7 degree difference in declination for sats to your south compared to sats from your extreme west, and even though I've written several computer programs to calculate the difference, and have even sat looking at balls and wooden models of sat dishes to understand, I never really checked to just see how much difference this made for real life sats.

Since the declination difference is up to ~ 0.7 in some cases, I've always been assuming that people who used the conventional method would typically be off by 0.6 deg for extreme sats.

Well I just ran my own program, and found out that the extreme cases where you can be off by 0.7 deg or so are for sats that I can't even SEE from my location. For example, from my location, the furthest west sat I could possibly see would only have a declination about 0.5 deg less than the declination of my true south sat.

So basically, while the 0.6 deg offset is still the most accurate way of aligning sat dishes, for most of us, the errors caused by using the conventional method won't exceed 0.5 deg for most of us, simply because we can't see the extreme sats. So I guess I understand now why people are content with using the conventional method, since the errors just aren't as big as I had assumed.

Anyway, I may go into hibernation for a while relative to insisting that people use the modified declination method.

 

[rogerduncan100]

Crappy SG2100 Bracket and Planes&Cones

I suspect my bracket is also far too flimsy. Just a little torque on the nut and it turns into a parallelogram! No wonder I can't get 30W.

I have been thinking a lot about the three dimensional geometry of satellites and dishes. I am going to try using Google Sketchup to analyse various planes and cones, hoping to find a way of determining how much to tilt the axis of rotation of the dish motor from perpendicular to latitude in order to get the dish to follow the arc as close as possible, or exactly if possible.

B.J., thanks for the neat programs! I noticed that both give the same answers for declination (that's good). My manual calculations were a little different but who is to say which are really correct. From 79 degrees to 30 degrees I get a declination difference of 0.30 degrees while your programs give a difference of 0.24 degrees for the same. My manual calculations trace a more curved arc. Thought you might be interested to know this. Obviously, it could be a mistake in my calculation method.

 

[Conky]

Heres my 2100. I put a dollar store spirit level on the yellow lines in the picture . The slanted lines indicate sitting on top of the bracket parallel to the bolts. I get from 30w to 125w

 

[rogerduncan100]

Wow. I wish my bracket was that straight. I seem not to be able to help myself but to over tighten the nuts!

 

[Tron]

Some of the older SG-2100s from DMSI had U-bolts that would strip very easily if tightened even a bit too much. The metal was some sort of soft pot metal, and it was common to destroy a U-bolt. They have since improved on the U-bolt quality, but I do remember having to buy a replacement set of U-bolts when I installed my first motor.

 

[adrian]

Motor level

See my post of yesterday on this forum regarding U bolts.

 

[B.J.]

Some of the older SG-2100s from DMSI had U-bolts that would strip very easily if tightened even a bit too much. The metal was some sort of soft pot metal, and it was common to destroy a U-bolt. They have since improved on the U-bolt quality, but I do remember having to buy a replacement set of U-bolts when I installed my first motor.

Re U-bolts, my NEW DMSI version had U-bolts that were spread out so much that the ends were about 3/4" wider than at the middle. I had to bend them to get them to either go into the bracket or to be able to tighten the nuts on the other end, because it flared out so much that the didn't even touch the open end of the clamp part that the nut is supposed to tighten on. But the worst part was that right out of the box, the nuts couldn't be screwed onto the U-bolts, even 1/8th of a turn. The nuts wouldn't go on good bolts of the same size, and good nuts wouldn't go on the bolts. I couldn't find my tap/die of that size, so I ended up FORCING the nuts over the U-bolts, which was not easy at all, but after doing that 5 or 6 times, it finally loosened up enough that I could turn the nuts by hand. But at first, I couldn't even turn the nuts with a cresent wrench... had to use a deep 6 sided socket, and when I got past the depth it would go, I took off the ratchet, and turned the socket with a vice grip, letting the U-bolt go through the square hole. But basically, the U-bolts, nuts, and the whole mount assembly is a piece of junk.
<br />
I just pulled up an OLD picture of my OLD SG2100. I wasn't sure where I had bought this, because the Sadoun sticker has long ago worn off, but I see now. Attaching 3 pictures below. The 2nd and 3rd show the Sadoun Digipower SG2100 sitting very flat on a pipe clamp I use to support the mount as I adjust azimuth. This OLD 2100 sits perfectly flat on any flat surface, and the various edges are all square. Also the top of the motor itself has a flat surface where the Digipower tag is, that can be used for adjusting elevation. The 1st picture is of my NEW DMSI 2100. It's hard to see in the picture, but the bracket doesn't sit flat on the same pipe clamp, or on any other flat surface. You can see space under the bracket, and it just rocks on a flat surface. It is of cheaper grade metal, and bends easily. Also I couldn't find ANY flat surface on the motor that could be used for elevation, although you can use the bent motor shaft once the motor is on the pole, and before you put the dish on. Also, these two motors have different designs relative to where the bolts attach to the motor, and to how the pointers point to the angle scale. I found the old scale fairly easy to use, once I figured out what part of the pointer to use, but this new 2100 has a pointer that is at least a degree off regardless of how you use it. I had a really hard time setting up this new 2100. I eventually used the back of the pole mount bracket of the 90CM Fortec, where it connects to the bent part of the motor shaft, as a surface parallel to the motor shaft, using the 90-decl-30 method described in another thread. That saved me from having to remove the dish to measure the angle.


Also, I'm not sure that one of the OP'er's comments was ever addressed. Above, it was mentioned:

The SG2100's 30 degree bend is itself a compromise. I think the only way to get a motorized dish to follow the arc perfectly is to set it up with the exact right bend for the latitude.

I just wanted to make sure that the OP'er realizes that this bend has nothing to do with the latitude. It is there to allow you to adjust for declination. Declination is a negative angle, but the dishes you attach to the motor shaft only allow you to tilt it at positive angles, so to get say a -5 degree declination, the bend in the shaft gives you a -30 declination, and then you adjust the DISH elevation to +25 to get a net -5. None of this involves latitude. This 30 deg bend also makes the axis of rotation go closer to the center of gravity of the dish, so that there is less torque on the motor. So it doesn't matter WHAT the bend in the motor shaft is, because it's accounted for by the dish elevation setting.

 

[rogerduncan100]

B.J. I agree with you after thinking about it for a few months. The amount of bend it the motor shaft doesn't affect how it follows the arc. You just make sure the axis of the motor is parallel to the Earth's axis.

I have given up my quest to change this from parallel to get a more perfect dish setup because the mathematics is difficult (parametric equations of cones).

I just finished manually calculating declination angles to south (79.3 degrees W), 30W and 125W and have found a difference of only 0.3 degrees. If I level my motor perfectly in the spring (when the weather is nice) all I have to do (theoretically) is aim 0.15 degrees high at south it will be only 0.15 degrees low at the extremes. That amount of imprecision is unfortunately necessary but probably doesn't make much practical difference.

 

[rogerduncan100]

PS: Despite what some say I still think I can use USALs to aim correctly. I will find out in the spring!