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Author Topic: My Review and Installation of the Powermax DG9120 Dish Mover  (Read 3433 times)
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elbandido
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« on: October 20, 2010, 05:41:33 PM »

 About a month ago, I decided to replace my StabHH120 that had been in operation since 2006. The replacement motor would have to handle a Geosat 1.2 meter because this is what was installed on the Stab. The Geosat actually measures 135cm on the vertical axis and 120cm on the horizontal axis, so this dish is about 4.5 feet tall. I choose the Powermax DG 9120 to turn this dish because it has a main gear that is made out of metal.
 The Stab HH120 was replaced because it would not follow the arc correctly anymore due to excessive backlash, and its motor is so slow that it seems to take several minutes for it to travel from 30 West to 127 West.
Stabs were considered to be a Cadillac of dish movers a few years ago. Today it is difficult to find many people selling Stabs. Most people are selling the SG line of motors which have been on the market for a long time.
 The SG 9120 is the strongest motor currently offered in the SG line. I have not seen anybody complain about this motor not being able to move their dish, but most motor users do not have a 1.2 meter dish. The SG9120 turns faster than the StabHH120 and this was one of the main reasons I wanted it. I did have some issues installing this Geosat 1.2 meter dish on the SG9120 and I will explain these issues or problems in detail.

Issue# 1 Maximum Motor Dish Weight:
 The Geosat 1.2 meter dish weighed 28 pounds without a lnb when it was attached to some cheap fish scales. The vendor says 38 pounds for shipping, so I am going to call it an even 30 pounds with lnb and its mounting hardware included. It is not hard to imagine this dish weighing 40 pounds during an ice or snow storm but we do not get that weather much here in Atlanta.
 I have read most of the SG9120 owner's manual and I can find at least two references to dish weight. It plainly says in the manual not to exceed the maximum dish weight for the motor.  I know that overloading the dish motor with too much weight is a bad thing; I originally bought the StabHH120 because it is rated for a weight that exceeds the weight of my dish by a good margin. The makers of the SG 9120 will not tell you what the maximum dish weight is, so how do we know if it is overloaded?
 The only way to know if a motor is overloaded is to measure the current that it is drawing. I spent some time measuring the current of this dish motor and I was a little bit surprised at how much power or current the motor used at the low ends of dish travel.
 The motor pulls about 200 milliamps for an instant when it starts and then it runs around 130 milliamps for most of the arc or about 30 degrees in either direction of due South. It will continue to pull this current if it is started in the middle and it will not vary much if the motor continues all the way to its physical limit in one direction.  For example, you can start at the center of motor travel, (85 West for Atlanta) and motor past 30 West and then on down to about 15 degrees West without seeing much over 200 milliamps of current bring drawn. 15 Degrees West seems to be about this motor's physical limit for Atlanta.
But when you start back up from 15 or 30 West, the current goes to 300 milliamps immediately at start-up and stays around 280-290 milliamps until the motor reaches 40-50 degrees West.

Issue#2 Dish Installation:
 The dish mounting hardware had to be turned upside down in order to mount this dish to the SG 9120 motor. The Geosat 1.2 meter dish has an adjustable rod for setting the dish elevation, and this rod would be in the way unless the entire mounting bracket is turned upside down.
The Geosat also has a bigger mounting bracket than some of the other 1.2 meter dishes and this caused the coax connector area underneath the motor to become crowded.

Overall Motor Performance:
 As far as strength and durability goes, the SG 9120 seems to have enough of both. The motor sounds good and its moving actions are good. You can grab the dish tube while it is running and realize pretty quickly that it takes a lot of pressure to get the motor to pull 200 milliamps.
 What they have done wrong in the design of this motor is they have allowed too much travel or stroke for the motor.  Most receivers will turn USALS off and give an “Out of Range” error when you move past 55-60 degrees of your latitude.  The SG 9120 will go way past 60 degrees and this is too much of a pull on start-up for most 1.2 meter dishes.
 This design flaw is probably why you do not see a published dish weight rating by the manufacturer. If a dish weight was published, it would have to rate the motor for its entire travel distance.

Conclusion:
 The Powermax SG9120 should make an excellent motor for the majority of the people that use motorized dish systems. This motor should last a long time turning a 1.2 meter dish, but its limits need to be understood.
I would not expect to have any issues with this motor if a 1 meter or smaller dish is used, and I would not hesitate to buy this motor again.
You can buy this motor Here: http://www.hypermegasat.com/SG9120-B.htm



Here is a picture of the dish mounted on the motor.
The dish mounting bracket has been turned upside down.


 El Bandido    10-20-2010
« Last Edit: December 24, 2010, 12:00:07 AM by elbandido » Logged
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« Reply #1 on: October 20, 2010, 06:46:12 PM »

Excellent review of the SG9120 Motor elbandido! I have read it 2 times now already, its full of good observations and documented test results. I am impressed with the amount of work you put into testing the motor and posting for all of us to read. The current draw especially is interesting.

The degree of rotation is interesting. The scale on the motor body goes from +/- 80 degrees. For some reason i seem to remember the factory sets the hardware limits at +/- 75. I also think that you can remove the label on the face of the motor and re-set those limits yourself if you want to. Im not 100% sure on that but if i get a chance i will check. I dont know if that helps with the issue or not.

Anyways thanks for the great review, im sure others will learn from it too.



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elbandido
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« Reply #2 on: October 20, 2010, 08:43:53 PM »

Thanks for the comments Hyper.
The only adjustment I found on the motor was the backlash adjustment. The backlash was set correctly from the factory so I wasted my time adjusting it.
There is a seal on the backlash adjustment screw that says something to the effect of the warranty being void if the seal is broken.
 
I did not try to manually set limits for dish travel or the degrees of rotation because I use USALS.  It does seem like I read something about setting them. Let me know if you find a written procedure as I might try it.
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foxtail
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« Reply #3 on: October 21, 2010, 12:50:10 PM »

You have to pull the tube right off the motor to adjust the limit. And yes it is under the label. There is no way of setting the limits with the tube and dish intac. So best to figure it out while you have the dish and motor on the ground. I know, i did just that last week!
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« Reply #4 on: October 21, 2010, 04:34:47 PM »

Good review and the 9120 is what I'm using with my 1.2M WSI dish.  The only comment I really have is that bend radius on the coax is too sharp and your changing the impedance a bit I would imagine.  I think I would try to just let the coax hang down further below the motor mount before curving it back.
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elbandido
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« Reply #5 on: October 21, 2010, 08:40:38 PM »

I am afraid to let the coax hang down because it almost got caught in the dish u-bolts. If that happens I have had a bad day.
Maybe I can find some 90 degree connectors. I think that is what I really need.
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