10' satellite Woes

[dedndave]

1. Focal Point
Refer to the picture in this post:
http://www.masm32.com/board/index.php?topic=13760.msg108295#msg108295

Notice that the focal point for C-band is a couple inches back from the front of the horn.
That point on the LNB should be 47.368 inches from the deepest (center) point of the dish.
I have seen a few threads where they report slightly better results
with the LNB moved in toward the dish slightly from that point.
That could be for a number of reasons, for example, they do not realize
that the focal point on the LNB is not at the face of the horn.
It could also help to acquire signals when the aim is off a little.
Although, tweaking this on one bird may not be a good idea.
If the dish is aimed correctly, you should get pretty
good results by adjusting it as we have calculated.
Keep in mind, these satellites do change position along the arc slightly over time.
Moving the LNB in slightly toward the dish could also help overcome this.

2. Declination Angle
Refer to the first picture in this post:
http://www.masm32.com/board/index.php?topic=13760.msg108279#msg108279

Right away, I do see a discrepancy between what that example demonstrates and
what makes sense to me. So, don't feel bad if you are confused.

First, the motor should point true south. The example shows a motor with a
30 degree bend in the pole. I don't know if that is what you have, but let's use it.

The example says the motor must have an elevation angle of (90-Lat) = 60.8976 degrees.
That seems a little off to me. If you were on the equator, the motor would need to
have an elevation angle of 90 degrees, yes. But, as you travel away from the
equator, there has to be a slight correction, so I don't agree with that formula.

We know the center (true south) elevation angle of the arc at your location is 56.1
degrees. We also know what the adjusted declination angle is for your location.
To me, the 56.1+4.23 = 60.33 degree value makes more sense.
Adjust your motor angle to 60.33 degrees elevation and make sure it points true south.
This is assuming you have a 30 degree bend in the motor pole.
If the motor elevation is 60.33 degrees and the declination is 4.23 degrees, the dish
elevation will be 56.1 degrees when it is aimed true south.

[z941998]

Go to www.sat-toys.com and become a member, instruction to align dishes are there with pictures/examples.  Also has automatic calculators based on zipcode to align the dish.  Sat-Toys has private boxes to watch direct tv / dish, etc at low one time costs.

[shankle]

Hi Guys,
Thanks for responding.
I have attached a small picture of the rocker arm.
It is in zip format of a .jpg image.
To the best of my knowledge I don't have a motor mount.
Am confused by the term. No 30 degree bend.
Today I will set the rocker arm to 56.17 degrees and the inclination to 4.21
and use the good old trial and error method and see what happens.
I will not mess with the Focal Point yet.

Thanks for the sat-toys site. Will check it out.

[dedndave]

great pic   :bg
step back so that most of the dish is in the pic and take a few more for us one from the front, side, back
it would be helpful to know what you have
or - maybe you can find a set of drawings of it online

[shankle]

Will send two more pictures as I think they would exceed the limit if sent all at once.
Also I have discarded the setting of the rocker arm to 57 degrees. It would push
the dish into the ground and be way in the trees. This can't be right. I did set the
lnb to .40" out from the scalar ring but still can't get anything.
1 picture attached.

[shankle]

2nd picture.

[shankle]

3rd picture

[dedndave]

that last pic helps a little
do you have the manufacturer and model number of the dish ?

EDIT - not the dish, so much, as the mount/motor for it

[shankle]

Don't know what manufacturer made the dish. All I can say about it is it's like that thing
Noah used - ancient 20 to 30 years old.

I actuator is a pro brand ball screw superjack (24")
Woks fine.

[dedndave]

i may have found part of our problem
i got the declination angle by interpolating from the table posted above
it must be an old table - lol
dishpointer.com says your declination angle is 4.8 degrees
i used a program from al-soft called Satellite Antenna Alignment and come up with ~4.85 degrees
attached is the report...

you can d/l the program yourself
http://www.al-soft.com/saa/satinfo.shtml
when it installs, it installs some adware called "Relevant Knowledge"
i blocked the adware from installing

i am going to take a closer look at your pictures and see if i can determine what some of the angles are
i will get back to you.....

[dedndave]

here ya go
near as i can measure, it looks like you have the inclination angle at about 32.5 degrees
i can't tell for sure - the picture is not square with the bracket, and the top of the bracket may not be level
the angles in the picture are what i think they should be
the inclination angle (top of the polar support) should be 29.1 degrees from level

[shankle]

Downloaded the report. Thanks.
The two satellites that I need to get me started are "nimik4 and satmex 5"

Nimik4 ku  82 degrees w
This one is very near the top of my arc here.
I have no idea what azimuth 179.005 is. I need how many degrees west of true north 0 degrees.
Should be 3 or 4 degrees west of true north.
Elevation 56.048. Is this a measurement on the face of the dish?

Satmex 5 116.8 degrees w is the lowest bird I can get that has c-band. The other birds that
are a little lower are worthless ku birds.
I have no idea what azimuth 234.58 is. I need how many degrees west of true north 0 degrees.
Should be 3 or 4 degrees west of true north.
Elevation 39.528. Is this a measurement on the face of the dish?

At the present time the LNB is set past the scalar ring .40" (might be wrong also)
For polarization it is set about 9:30 o'clock. (when dish is straight up)

[dedndave]

according to NASA, true north is currently 5.03 degrees clockwise from magnetic north for your location
in the daytime, you may be able to use the sun to find the true heading - there are astronomy websites for that
astronomers use Polaris (the north star) to find true north - that might be another approach - don't trip over the garden at nite   :P

56.048 degrees is the elevation above the southern horizon to sight the bird
so, that is 90 degrees away from the vertical face of the dish'

when the dish is straight up and down, the isolation bar should be level across the cavity
you should be able to acquire signal, even if the polarity is off
some of the birds have horizonal polarity - some have vertical - it should not be that critical

[shankle]

The figures on the image are very close to how I have them set. Hard to measure
fraction of a degree with an inclinometer.
Never thought to check bracket A for level. Will do that tomorrow. I checked the sides
of the polar mount for level with the inclinometer.

Still have problems with terminology.
How and where do I set the 56.048 elevation? Or is this something that occurs
as I rotate the dish?
What is the "Isolation Bar"?
Think I can now hack the magnetic North . Thanks.
I know the questions are elementary to you but I am a true novice at this.
Actually my 2nd time. How I ever did it the 1st time is a mystery. It was an
Orbitron 8' with a manual. I am not looking forward to doing this the next
time a hurricane passes by. Maybe another tree.

[dedndave]

we can make fairly accurate measurements with the camera
if you put a bubble-centered level in the picture nearby, we can use that as a reference line
it is important that you put the dish at the center of the arc (high point)
it is also important that the camera is perpendicular to the polar mount and at the same height from the ground
if the camera is tipped (rotated cw or ccw) a little, that won't matter
we can use the pixel x,y positions to calculate precise angles with a little trig
oh - don't get too far away - the more pixels, the more accurate the calculations
don't get too close, either - i need to find a few points

if we wanted to get fancy, by knowing the turns per inch of the adjustment bolts and a few other measurements,
we could calculate how far to adjust the bolts (how many turns) to get the angles we want

the 56.05 degree elevation is the angle of an imaginary line from the center of the dish to the satellite
the angle of that line above the horizon (i.e. level line) is the elevation of the bird
if you add the angles together in the pic, you can come up with 56.05   :bg
calculate the angle of the back of the dish: 29.1 + 4.85 = 33.95 degrees
that angle is 90 degrees (perpendicular) from the imaginary elevation line, so 90 - 33.95 = 56.05 degrees   :U

something to notice about the declination angle - not important to know, but interesting
for imaginary "birds" on the east and west horizons, the declination angle is the diff between e/w and the resulting azimuth
so, if there was a bird at the east end of the arc, on the eastern horizon, and you pointed the dish at it,
the resulting azimuth of the dish would be 90 + 4.85 degrees (4.85 degrees south of true east)
likewise, at the western horizon, the resulting azimuth would be 270 - 4.85 degrees (4.85 degrees south of true west)
in the center of the arc, the elevation is 56.05 degrees and true south
those 3 points define the arc

also interesting - they call the band of satellites the "Clarke Belt"
it was Arthur C. Clarke (one of my favorite authors) that theororized that satellites at a precise altitude would be geo-stationary
he said that 3 satellites at 120 degree points around the earth would give full coverage
not bad for a science fiction writer in 1945, eh ?
it was Arthur C. Clarke and Stanley Kubrick that wrote "2001: A Space Odyssey"

the isolation bar is inside the LNB - refer to the pic in this post:
http://www.masm32.com/board/index.php?topic=13760.msg108262#msg108262
he also said that, as he stood in front of the dish, the Ku band convertor was at 45 degrees down and left
this adjustment was made with the dish at the center (high point) of the arc
getting the focal point right is far more important than getting the polarization right