Tif,
Okay, if you absolutely must install a roof mount, that will be acceptable. But, here is some advice and a few tips from me to help you make the process easier.
1] The roof must be VERY solid. If you walk around on the garage roof and you can noticeably detect that the roof bows and sags under your weight, it won't be solid enough to accommodate the dish. I don't mean to infer that the dish will fall through the roof, but that you will have a hard time keeping the mast perfectly plumb. Just your weight may affect the alignment (even if it is just a minor affect). If you get it aligned just perfect, then when you step away from the dish, the mast alignment will change and you may lose your signal lock. Or, if the wind blows, the force on the dish will flex the mount and throw the alignment off, too. Just a mere 1/8" change in the mounting platform will throw your alignment off.
If it is a wood-frame roof, try placing the dish mount nearer to an eave or sidewall where the roof support is more rigid. That should resolve that problem for the most part if the roof is fairly sturdy.
2] To avoid a lot of trips up and down the ladder, run an extension cord up on the roof. Take your satellite receiver up on the roof along with a portable TV. Make your dish / motor alignment adjustments while monitoring the signal level and quality meters directly. If this is your first setup or you consider yourself to still be a novice at alignment, you won't win if you have to make an adjustment and then scramble down the ladder to check the results and then back up to retweak it. It doesn't help to have your spouse or a friend monitor the signal and call out to you, either. Even for a ground mounted system you should apply this tip. There is absolutely no substitute for the immediate feedback that you get from having the signal monitoring device right in front of you when you play around with the adjustments.
For an example of what it may be like, (if you have an idea that you can manage it otherwise), simply try to play a video game blindfolded and have someone else call out the moves that they think are required. Trust me, you will fast become frustrated with the results. End of game!
3] Last chance to install it on the ground. You could set up a nice looking (aesthetic) rock garden with the dish at the center and a RR tie boarder around it like you would for planting a tree or shrub. No lawnmower worries there. Just mow around the border and you won't worry about hitting the mast pole.
4] Obviously, it is all up to you. You are the one who will have to do all the setup and alignment, maintain the dish (keep the snow off) and realign it after a major windstorm. I would just like to clue you in, in advance, that you are going to be spending a lot of time at the dish, especially in the beginning, so make it as convenient as you possibly can for yourself. Even if it is installed on your garage roof. Plan ahead. You will have to trust me (us) on this issue. We have been there, done that and we really want you to take advantage of our past experience so that your experience will be more pleasant.
RADAR
Excellent advice Radar. Thanks for taking the time to post.
What I plan to do is mount a schedule 40 2 inch pipe on the outside garage wall that is buried in a concrete footer. The pipe will extend up through the eave and protrude above the actual roof. On the top of the pipe I plan on welding a 1/4" plate large enough to bolt the J mount of the dish to. I also plan on making a hole large enough in the top of the pipe mount to pass the coax down through and then back out just under the eave and then around the house to my receiver. I feel this mount should prove solid enough to hold the dish with it being secured to the building and also the concrete footer. I understand that everything has to be beyond perfect when it comes to being plumb.
A rock garden and railroad ties sounds like a nice idea but with a Backhoe and large tractors it wouldn't take much to destroy the dish if you happened to bump it. I feel safer with the dish up where no one should be able to hit it..
I have a power outlet just under the eave that I can use for powering the receiver on the roof while setting up. Sounds like a good plan to have everything on the roof while tweaking.
