Install on Rohn 20G Tower

[gregaj]

Hello All,

I just received my M-2 Motorized Bundle from Sadoun yesterday and plan on attempting the installation this weekend. In the past I had a DirectTV dish mounted on my Rohn TV tower (about 20 feet up) and it worked fine. Obviously the dish is larger (getting the FS80P) 31" dish, so I was wondering what the group thought about this? I never had any problem with tower movement with my directTV system, so again I'd like to try this for my FTA Sat. I live in southern Indiana and am new to FTA sat?

Thanks,
Greg Johnson

[elgemcdlf]

Where in S. Indiana? It all king of depends on how your tower is oriented. I assume it is of the 3 leg variety. If so you will want one of the legs due south (assuming you are wishing to mount to one of the legs). RadioBob has one mounted on a tower and I am assuming he has full travel of the motor. The DN dish did not move so as long as it could be aligned to see what it needed to see all was good. If a flat side is due south you will most likely need to fashoin some form of mount that extends the motor assembly out away from the tower so it will have clearance when moving.

[gregaj]

Thanks for the information. I live in Santa Claus, IN. Yes, the tower is the 3 leg variety. I'll have to check and see, but I do think one of the legs points almost due-south.

[elgemcdlf]

I am halfway between Terre Haute and Vincinnes just off 41

[wejones]

Unless the vertical elements are perfectly plumb, aiming directly south, and of the right diameter, it will probably be better to fabricate some kind of standoff mount anyway. You need to mount on a pole that will allow you to turn the whole assembly on the pole, and this pole should be plumb, or else it will make it difficult to align.
Something like this might be appropriate, but you'd probably want to figure out a way of making sure it's plumb:

[gregaj]

Bill, thanks for the information. Can you tell me how many degrees does the disk need to swing? I assume about 180deg?

Thanks,
Greg

[wejones]

Originally Posted by gregaj

Bill, thanks for the information. Can you tell me how many degrees does the disk need to swing? I assume about 180deg?

Thanks,
Greg

As far as turning the whole thing on the pole, that's just a few degrees, while you're searching for your true south. However, with respect to bumping into what it's mounted on, I'm not sure. Those motors don't turn 180 deg, something more like +/- 60 or so, but as it turns, the top side of the dish will start to bump into whatever surface it's mounted on, if it's not extended from the surface. Like Steve said, if the corner is to the south, then there probably will be enough clearance. You may not need to, but it's probably safer to assume you're going to extend it a few inches.
I guess that when you get the thing, you could temporarily hook it up, and run the thing 60 or so degrees off center, then check to see if it bumps into anthing. Perhaps radiobob can comment, since he's done it. I only dream about having a tower.

[radiobob]

gregaj:

I did have mine mounted on one leg of my 25G tower, and the dish was able to complete its full arc unimpeded. But, I discovered that Katrina had moved my formerly plumb tower just a couple of degrees off and that effectively put an end to that scheme.

I "graduated" to a short mast attached to a tree stump, but when the stump began decaying, I had to come up with "Plan C" and stuck a fence post in a wash tub and filled the tub with concrete. Ugly as sin, but works great! (Yes, digging a hole and planting the mast would probably be preferable, but I wanted something vaguely "portable"...as if a tub with 200 lbs. of concrete is portable!).

One of the challenges of tower mounting is that assuming the tower is close to the house, one must mount the dish fairly far up to get a good view of the full arc. When you have to work on the dish, motor, cables, etc., this means either setting a ladder up beside the tower or strapping on the ol' climbing belt and scaling the tower.

All that said...if your tower is plumb and situated in such a way that the motor can steer the dish through the whole southern arc, give it a shot!

[William Eng]

Greg

Unless you have major obstruction issues (trees, buildings, etc), it would be much better keeping the whole thing close to the ground. If you have never installed a motorized dish before, plan to have a couple of days free. And why take the risk falling? Besides as RadioBob says, the higher you are, the more wind the dish will feel so you will risk the thing blowing out of alignment.

I used to work weekend accidents at the Houston's medical examiner office so I have seen plenty of people breaking their necks falling off their ladders, roofs, etc.

[wejones]

Originally Posted by gregaj

Bill, thanks for the information. Can you tell me how many degrees does the disk need to swing? I assume about 180deg?

Thanks,
Greg

I just did a little experiment. I turned my dish to the last sat I have in memory (before my garage gets in the way), and that turns the motor about 57 degrees ( +/- a few tenths) . I went out and looked at the dish, and it is just at this angle where the dish would hit the same plane that my pole is in. Ie see:



I'm at about 44.1 deg latitude, so the motor elevation is relatively low. People further south might have a higher motor elevation, which might make the dish hit an obstruction with less of a swing.
BTW, this 57 deg swing comes from about a 53 deg difference in longitude between you and the sat. So from the picture, I think you can get an idea of just to what extent the tower or whatever the dish is mounted on might interfere. Ie if the dish is mounted on a tower with the flat surface south, 57 deg swing would be about the max before it hit the other side of the tower, but if one point of the triangular tower were south, it looks like you could travel the full swing of the mount. Also, depending on what sats you're interested in, you may not need 57 deg swing.