SP-120 H-H with Geosat Pro 90

[wbarrett]

Spent a frustrating week setting up my new-to-me ku system. I’m using the SP-120 H-H motor from Hyper with a Geosat Pro 90 cm dish.

Spent days setting and resetting latitude, declination and elevation per the instructions.

First, I discovered a typo in the SP-120 instructions to be aware of:
The formula for setting declination is listed on page 2 II-2 as setting the declination by 40-declination angle in table on page 6.

So for 33 latitude, elevation on motor is set to 57 and declination on dish is 40-5.377 = 34.6 per the instructions. Tried that…

Nope!

I finally measured the tube angle and it is 30 degrees not 40.  So the declination was actually 24.6. The formula should be 30-declination angle for the SP-120.


Still didn’t work!  I realized that the SP-120 instructions also assumes you are using a prime focus dish.

Time to think all these angles through.

So I dug into Geosat Pro 90 specifications.  The offset angle is 24.52 degrees. I also measured the lnb arm angle from horizon and found it to be 17 degrees.

So for my due south satellite of 87.1w, the satellite from dishpointer is 51.4. So I finally found 87.1w by:

51.4 satellite declination
-24.5 Geosat Pro offset angle
=26.8 degrees that the back center dish should be

But that was too hard to measure.

Then I realized that if I measured on the lnb arm, the angle should be:

  26.8 degrees
+17 degree horizontal arm angle
=43.8 lnb arm angle

Set the arm angle to 44 degrees and bam, I got her!

HTH the next newbie (like me)

[Hyper]

Great job wbarrett!


And thanks for showing your work too!


For sure will help some folks.


I did not know about that typo on the SP-120  << good to know


Would love to see some pics of your new motorized Ku dish.



 

[elbandido]

Trying to setup a ku dish motor for the first time can be an aggravating and frustrating experience. Every ku motor manual that I have read is confusing at best when it comes to setting dish elevation.  In reality, setting motor and dish elevation is not terribly complicated. Knowing the advertised offset in degrees for a particular dish helps, but many consumer type offset dishes do not list or offer this information.

The dish motor elevation should be set the same as your latitude. Set the dish motor elevation Once, then leave it alone. The dish motor elevation should not be changed or adjusted for most systems.

Set the dish on the motor pole without the motor, then precisely aim and adjust the dish for the satellite you will use as South.  Protractors or angle finders will give different readings, depending where the are placed on the dish. Place the protractor or angle finder on the dish while it is aimed at the satellite you want to use for South, and make a note of what angle it reads. Mark the exact spot where the protractor or angle finder is on the dish by using a felt marker or similar. Remove the dish from the pole.

Install the motor on the pole and verify motor elevation equals your latitude. Install the dish on the motor. If the protractor or angle finder was removed from the dish, then reinstall it on the dish in the exact location it was before. Set the dish to the same angle as it was using the previous protractor or angle finder reading. You should now have a fairly correct elevation for the dish and motor.