SatSig topic:

Pointing dish with motor

(Read 13444 times)

Jun 20^th, 2006 at 2:20pm

Hello.

My name is Rui and i live near Lisbon, Portugal.

I have a 80cm dish with a Metronic motor.

And i want to know what kind of setup should i do to the motor elevatio, dish, elevation, LNB polarization, (someone told me that should be vertically)

Thanks in advance.

Jun 20^th, 2006 at 6:48pm

It sounds as though you have a satellite TV system with a motor driven polar mount.

With the motor centralised, and the feed rotation (polarisation) upright the whole head unit needs to be aimed accurately true SOUTH by rotating the pole attachment clamp.

As far as set up angles are concerned it is only your latitude that matters. Assuming it is 38.5 deg and using the calculator at https://www.satsig.net/ssazelm.htm the angles you need are the main motor angle of 39.2 deg and a small downwards tilt of the dish itself at -5.4 deg. The total beam elevation towards a due south satellite 45.4 deg.

The scales on your motor and dish may differ. Have a look at all the examples https://www.satsig.net/polmount.htm Can you send me a close up digital photo of the motor and the associated brackets etc. eric@satsig.net

If you can set the angles correctly you should then be able to drive the dish east and west ans see all satellites.

Best regards, Eric.

Jun 21^st, 2006 at 12:49am

I thank your reply.

The coordinates where i am are:

Latitude: 38.6614
Longitude: -9.0510

Polar mount main axis angle (deg)=39.36
Polar mount dish offset tilt (deg)=5.41

Motor elevation: X=90-39.36=50.64

Dish elevation:Y=40-5,41=34.59

True south for my location is about 5 degrees West? Right?

Are these correct?

Tomorow i will post some pics of my dish and my polar mount motor for you to analise.

Thanks

Jun 22^nd, 2006 at 3:05pm

I have mounted the motor+dish as it should be, all aligned, but I still can't make it work...

Here are the pictures...

Dish:

. . . Motor:

Jun 22^nd, 2006 at 8:31pm

South: If you make the north end of the compass needle align with N or 0 or 360 on your compass scale then the magnetic bearing angle of 185 deg corresponds to true south.

As far as the mount is concerned I really need a further picture that shows all parts of the motor and brackets from the side view in one larger picture.

I suspect that the scale on the motor bracket should be set to 39.4 deg or it may need to be 50.6 deg, depending which way the scale goes. If the motor axis is tilted only a few degrees above the horizontal a low number like 20 deg should be visible, but it may read 70 deg. Use common sense, the motor axis needs to be 39.4 deg above the horizon, approximately pointing to the north pole star. Check at night.

The elevation angle scale on the dish is intended for use when the dish is directly attached to a vertical pole.
I suspect that there is a cranked arm attached to the motor. What is the angle of the crank? Could be 30, 40, 50 deg perhaps. The effect of the crank is to offset the elevation scale. So if the crank angle is 50 deg then setting the elevation scale to 50 means the result is zero. Your beam will be exactly at right angles to the motor axis. You need -5.4 deg however. So, set the scale the same as the crank angle and then go down 5.4 deg.

Best regards, Eric.

Jun 23^rd, 2006 at 9:22pm

Here are better resolution pics and showing all the pieces mounted together... click on the picture to view a bigger pic...

https://img488.imageshack.us/my.php?image=p10005150ag.jpg
https://img315.imageshack.us/my.php?image=p10005164wg.jpg

https://img180.imageshack.us/my.php?image=p10005192mv.jpg
https://img180.imageshack.us/my.php?image=p10005204dl.jpg

I hope this pics you can see it better.

Thanks for your help till now...

Jun 23^rd, 2006 at 10:41pm

Motor
The angle looks OK to me. I've measured the angle to be 39 deg which is what is should be.

Note it is the motor axis that matters i.e. 90 deg angle to the slope of the motor bearing ring.
Your scale reads 51 deg.

Dish angle
The cranked tube appears bent at 40 deg. So the required angle is 40 - 5.5 = 34.5 deg. You seem to have set this right. Check that the centre hole is pivoting on a dimple, otherwise it may fall down a bit and give scale errors of 5 deg or more.

Here is a suggested carrier to look for:
Divona 11.544 GHz Horizontal 17577 sps 7/8 FEC on Atlantic Bird 3 at 5 west.
ref: https://www.lyngsat.com/ab3.html
You should be able to find this with the motor preset just a little to the left of the centre position.

Tomorrow, 24th June, the sun will be due south of you at 12:35 GMT and due west at 16:32 GMT.

If you have problems I suggest taking the dish down to ground level and practicing till you can track all the satellites. You will be able to have your receiver and test equipment nearby.
Once you can see many satellites, move it to the roof where the only variables will be how accurately vertical is the pole and which way is south.

Unless the main motor angle and dish downwards tilt angle are pre-set accurately by calculation and measurement you may spend a week or more making small adjustments trying to get it right.

Best regards, Eric.

Jun 24^th, 2006 at 2:05am

Thanks for you sugestions.

I have one more question, i should memorize in the receiver the positions of the satelites before i mount it? I ask you this because my dish is mounted on the roof of a building and getting to it its very dificult. If i could memorize sat positions(angles) at home it would be very helpfull, because i cand mount it on the ground because i have very tall buildings on my area.

Im 100% sure that the pole is absolutely vertica!

Could we talk on MSN? I have several questions concerning the meaning of some thecnical words that you have used like "Check that the centre hole is pivoting on a dimple" Shocked

Thanks

Compliments
Rui Parrula

Jun 24^th, 2006 at 9:21am

Since you can drive the motor by remote control I would only save the satellite locations after I had finally mounted the dish. You will need to make small adjustments to set the main clamp accurately due south and each time you change this all the motor positions will change.

If you are not pointed accurately due south you will not see the satellites in the far west and in the far east.

The scale and adjustment mechanism on the back of the dish has two bolts and two curved slots. There is no good centre bearing about which it rotates. There is a hole in the middle of the outer metal part. Often there is a corresponding small raised dimple in the metal underneath which is supposed to act like a bearing. If it is not in the centre then the scale may give big errors of several degrees.

I have no idea how to talk on MSN.

Best regards, Eric.

Jun 24^th, 2006 at 11:04am

You mean the hole in the motor arm where the dish is fixed? I may need to correct the positioning of the dish in the motor arm?

Thanks.

Jun 24^th, 2006 at 4:33pm

No. I refer to the small circle approx 6mm diameter visible the centre between two curved slots on the dish bracket. The circle is approx mid way between the two bolts. If it is not a hole it must be the backside of the dimple, which then goes inwards into a hole in the inner metal sheets. I may have mistaken the back of the dimples as holes.

Either way it is important that the weight of the dish does not allow it to fall down a bit as the scale/tick mark will give quite false readings if the dimples and holes do not align. The dimples and holes on both sides must align to form a central 'bearing' for the dish up/down movement prior to tightening the bolts.

In this image the dimple/hole is at the top and the scale is set to 42 deg, not 34 deg.
Best regards, Eric.

Jun 27^th, 2006 at 10:11pm

Then i must correct the values?

Its a hole betwen the 2 curved slots, and it has a relief that fits into the hole.

But the last picture os the dish points do 34,5... that picture was taken before the correct values being entered...