DG-380 elevation setting clarification

[skysurfer]

I'm going through things right now to try to figure out why I"m off the arc and I decided to read the DG380 manual to see if I am missing something.

When I got the motor and installed it, I set the elevation scale (the motor bracket/motor elevation markings) to my latitude of 35 deg, thinking this motor was like my other motor, a stab.

When I read the manual, I can't help but think it's saying to use the Elevation and Declination Angle Table leaflet to find your elevation angle to set it at.

Looking at 35 deg site latitude in the leaflet, it says the elevation angle is 55 deg.

Should I keep my motor set where it is at 35 deg or use 55 deg on the scale of the motor bracket/motor elevation markings?

If I"m fine, then I have to look at polar axis things and dish bracket elevation (WAG there since I had to invert the fortec star 90cm bracket to work with this dg380, but I did find my due south sat and peaked it up but my arc falls off about 20 deg to each side and first thing I checked was that my pole was plumb).

 

[Mr Tony]

elevation or latitude scale?

If it says elevation then its 55 (90-your latitiude)

I know on my SG2100 there is a latitude and a elevation scale. Latitude is the same as yours but elevation is 90 minus latitude (I luck out because I'm at 45N so its the same)

 

[skysurfer]

I"m talking about the angle adjustment on the motor bracket, not the dish bracket since I"ve WAG'ed the dish bracket.

Unless the geometry of the stab and the dg380 are very different, it seems weird that stab would be set to my actual latitude while the dg380 would be set to the elevation angle column of that leaflet.

 

[skysurfer]

and now I have to wonder if sadoun has changed the design - my motor bracket says "Latitude", while the instruction manual's motor bracket illustration says "elevation".

 

[brentb636]

Both sides of the DG380 bracket are for latitude, so set it at 35 degrees. Generally, once that's set , you won't tweak it anymore.

 

[brentb636]

How about pics? Why exactly did you have to invert the dish ?

 

[skysurfer]

i had to invert the dish bracket otherwise I could not slide the bracket on the motor pole due to the dimple that sits on top of a post or upward-facing motor tube under normal installations.

I wonder if I need to invert the dish also or if the FS is built properly that the dish is facing the right way even if the bracket on the back is upside down from its instruction manual installation orientation.

 

[brentb636]

That dimple can be cut out with a hacksaw. That's what I did with my Fortec 1.2M dish bracket, and it works just fine. I notice in Sadoun's 1.2M pics, that they cut out the dimple, too. If you can slice it out of there, then mount the dish straight up, maybe you'll get better results. A pic would be nice. [edit] The STAB HH100 and STAB HH120 motors both are "upwardly " oriented motors, and I wonder if these particular brackets were made with Those motors in mind.
Here's a pic from Sadoun that shows the dimple cut away at the top of the bracket. http://sadoun.com/Sat/Products/Fortec-Star/Dishes/Fortec-120cm-DG380.jpg

 

[turbosat]

Skysurfer I ran into those instructions with my 380 motor, confused me because I wasn't reading it closely enough. Page 2 of instructions, #3 explains adjusting the "antenna dish"'s scale to read 35-minus your declination. The #2 thing explains setting the motor's elevation to your latitude. I had to make a bracket for my dish too, but I was making the motor alignment much harder than it actually is, haha, by not understanding the instructions.

 

[skysurfer]

i guess i'll be cutting out the dimple and trying that and see if it gets me on the full arc. it will make getting the dish bracket to the motor tube axis harder because I was using that dimple as well as the mold mark or junction on the tube to help me with that part of the alignment.

if anything, it will at least eliminate one possibility of why I'm not tracking the arc right.

On my stab motor, that dish tracked the arc perfectly while the bracket was dimple-upwards, so it should do the same on the dg380 with dimple removed to keep that portion of the bracket upwards.

 

[brentb636]

I agree, and hope that this is actually the problem.

 

[Othea]

DG380

I think you have to use the Elevation and Declination Angle Table, which shows "Your Elevation Angle *minus* Declination Angle."

At 34°, mine is 29.5 according to the table. I first set the motor at 35° but that was off with my WSI9036 dish. At 29.5°, it was pretty good. Now at 28° it's tracking the arc just fine. You can just set your motor angle according to the table, as suggested, but if you're like me, you probably will have to tweak another 1-2 degrees for best performance.

True, the manual is not clear -- the 35° seems to be just one possible example.

 

[B.J.]

I think you have to use the Elevation and Declination Angle Table, which shows "Your Elevation Angle *minus* Declination Angle."

At 34°, mine is 29.5 according to the table. I first set the motor at 35° but that was off with my WSI9036 dish. At 29.5°, it was pretty good. Now at 28° it's tracking the arc just fine. You can just set your motor angle according to the table, as suggested, but if you're like me, you probably will have to tweak another 1-2 degrees for best performance.

True, the manual is not clear -- the 35° seems to be just one possible example.

This post is very confusing, possibly because two people just happen to have latitudes that are nearly the same as the motor shaft bend angle. I'm not exactly sure whether you're talking about the motor setting or dish setting here, but I thought I would try to clarify things a bit before there is more confusion
First, there is no "Your Elevation Angle *minus* Declination Angle." calculation involved. The table referred to subtracts declination from 35, and this has nothing to do with your latitude or your elevation angle or anything like that. THis 35 in this calculation comes from the angle of the bend in the motor shaft. DIfferent motors and sometimes different replacement shafts on the same motor will have different bend angles. The table in the manual assumes that the motor shaft is bent 35 degrees, which is apparently the bend angle in this particular motor, so you subtract your declination from 35. If you have a shaft with a different angle, for example the bend in my SG2100 is 30 degrees, so I subtract my declination from 30. Other motors have bend angles that are 45 degs, and one has a 46.5 deg bend, so the calculation is different for different motors.
The angle calculated here is for setting the DISH elevation, not the MOTOR elevation. It is really just a way of setting your declination, which is a negative angle, but since the dish mounts don't go negative, there is the bend in the shaft that gives you a 35 deg declination, and to get your actual declination, you raise the elevation of the dish 35 deg minus the declination to give you the proper declination angle.

Secondly, as mentioned above, the angle on the motor scale should be set to your latitude (actually your latitude plus 0.6 deg, but I won't confuse things more with that now) if it's a latitude scale, and it should be set to 90 minus your latitude, if it's an elevation scale. If your latitude is 34 and you set your MOTOR to 28, then there is NO WAY that you are tracking the arc properly. The motor scale will not be off that much. The scale on dish mounts can often be off that much, but not a motor scale.

 

[turbosat]

Thanks for the info bj, now if I can just remember that !! Maybe I will print it and post it on the wall LOL.

 

[DishDigger]

""I'm going through things right now to try to figure out why I"m off the arc and I decided to read the DG380 manual to see if I am missing something.""



I ran in to the same problem when inverting the mounting bracket on my 1.2 meter dish and using the DG380. The information WITH THE DISH stated that when inverting the mount for downward pointing motor shafts, subtract 4.5 degrees from the elevation angle. This may just pertain to the 120X135CM dish like the one I got from SatelliteAV, I don't know, but thought I'd mention it . The info for the DG380 DOES call the adjustment on the motor the ELEVATION ANGLE (A), but says in the definition to set it to your latitude . You have to be very careful when trying to keep it straight. I sat down and wrote mine out on paper after carefully calculating all the angles. When I put the dish on the calculated angles, after telling the DiSEqC control to go to 91W, and I got a quality in the 80's!:up I kept it straight by looking at the diagrams and not worrying about the terminology.

 

[skysurfer]

I ran in to the same problem when inverting the mounting bracket on my 1.2 meter dish and using the DG380. The information WITH THE DISH stated that when inverting the mount for downward pointing motor shafts, subtract 4.5 degrees from the elevation angle.

I'm aware from a post I saw a few days ago that the Geosatpro 1.2m dish has that info in their instructions. I have a FS 120cm dish but may get a geosatpro one someday.

I took the dish off the pole and cut off the dimple part of the bracket. I think it's actually nice this way as if my dish slips, the rolled outer lip of the motor tube should be able to keep the dish from falling off the tube.

I put the bracket back on the tube, aligned the dish axis to the motor axis as best as I could, and I made a final decision that since the motor bracket says "Latitude" on it that I would set it to my latitude. I checked that and it seemed a little on the low side (towards 34 deg instead of 35 deg). I adjusted things to just a hair over 35 deg to account closer for the 35.06 deg of my latitude plus the .6 deg thing that bj mentioned.

it got dark before I could put it all back up on the pole and see where I stand after the modification and motor latitude touchup.

 

[AcWxRadar]

Latitude = Latitude

If you live at "This Is My City" and the latitude coordinate for "This is My City" is "XX.X" degrees, set the angle on the MOTOR latitude scale to "XX.X" degrees.

If your motor happens to have an "ELEVATION" scale on the opposite side, then Iceberg's information will provide you with a bit of a redundancy check... 90 degrees - LATITUDE = ELEVATION. So the elevation scale reads the difference between 90 degrees and the latitude degrees.

For a H-H (or DiSEqC motor), this is the only angle you need to be concerned with. Set the motor Latitude to your site's Latitude and you will be done with that.

The only time to adjust this angle is if you did not or cannot read the Latitude angle precisely. You should never be very far off.

The most you can be off is just a few tenths of a degree and that is only because the Latitude degree scale (on the motor) is not marked out in that fine of increments, so some guess work is often necessary. Normally, you will be doggone close. These motor scales for latitude are quite accurate, so any error is likely going to be due to your own eyesight or judgment regarding what is "xy.2" degrees VS "xy.4" degrees... Or .6 vs .7 vs .8 etc.

I am sure that you understand what I am trying to say in that regard.

This is all you need to worry about for the motor adjustment (well, except for the azimuth pointing, but that is entirely different from this).

RADAR

 

[Othea]

Thanks for the correction

Thank you the clarification BJ. Yes, my terminology and math are no good, and I misread the manual's table. No surprise there, since it 's not clearly written.

Installation of this motor was counter-intuitive for me, since I also have a STAB motor bracket properly set at my latitude.

With my DG380, things did not go quite as smoothly. I tried 34° on the motor scale (and I also tried the manual's suggestion of 35° just to be sure), but that didn't work.

Here's what finally did work (at my latitude of 34°): I set my motor bracket scale to 28° and my dish bracket scale to 38°. I can track the arc from AMC5 to G18 with approx. 98% quality on Ktel, close to 50% quality on RTN and 70-78% quality on the Equity channels with a Merc II and 90cm dish. I forget what my quality is on AMC21, but it's not too bad. Trees won't permit me to go any farther east or west.

How can that be at 28°? Well, I now remember that I had to order a 42mm tube to replace the 55mm tube (or was it the other way around?). Perhaps that changed the motor bend angle, so that my scales on the motor and dish brackets are now way off?-- Anyway, that seems to be what your post suggests to me upon reflection.

 

[AcWxRadar]

Dish Elevation

When it comes to the dish elevation setting, this is where the declination angle comes into play.

The bend angle in the motor tube (you see that it has a step to it) and your declination angle (which is based upon your site's latitude) is what decides this setting.

Generally, the MOTOR manual will discuss subtracting so many degrees called the declination angle (based upon your site's latitude) from a constant (25, 30, 35, 40 or 45 degrees - based upon the angle of the motor tube bend).

The difference is the angle where you should set your dish elevation bracket.

Again, there is some "fudge factors" here as well and not all charts that are printed in the manuals are precise for every location. They are merely tools to get you into the ballpark and doggone close to a home run. But, you still are required to do some finer tweaking to peak the signal.

Peaking the signal is always the final word.

I recommend ignoring all angles except the latitude angle of the motor. If you are setting your dish and motor up at you own home, you might do better experimenting without any angles for your guidance. It is a good practice adventure, in my opinion. A learning experience.

I began with my first dish setup by only "guesstimating" where I should be aiming. I was using a fixed point dish back then, but it really helped me learn where the sats were on my horizon. If you try this, you should try it with a fixed point dish first. Before you apply your motor.

This provides another advantage - you can record your BEST signal and QUALITY levels when you know you are "spot" on with the satellite. You can use those readings to compare with the readings you get after you have the motor installed with the same dish. If is a nice reference figure to have.

It is good to come up with several "redundancy" checks. Anything that you can find that helps is good!

Good luck and have fun!

Radar

 

[Babadem]

The more expalanation the better. I hope I don't get confused in the end.