Actual Dish Elevation with HH100

[shrugy]

Hi,

Let's say that I completed all the rotor + dish instructions as illustrated in:

http://www.sadoun.com/Sat/Installati...stallation.htm

What should be the actual measured elevation angle of the installed dish while it's still zeroed out on true south?

My lat. is 37.13N and long. is 80.42W. So I set rotor elevation to 37.13 and the dish elevation to 24.1. When I measure the true elevation angle of the dish with this setting while it's still pointing on true south, I get a reading of about 38 degrees using Johnson angle reader. While, AMC 5, which is almost located at my true south (off by 1.6 deg.), requires a dish elevation of 46 deg. as per the elevation and azmuth calculator in:

http://www.sadoun.com/Sat/Installati...Calculator.htm

So, there is about 8 degrees difference between where my dish should be pointing and where it is actually pointing as a result of the installation. Since I checked all the numbers so many times, and checked my installation against the manual and instructions online, and they all look in order, then I can only guess that there is either an error in dish elevation calculation for HH100 or an error in the elevation calculation for AMC 5 for my location. The best way to find where the error might be is to figure out what the actual elevation angle of the dish should be while pointing at true south. Anyone knows how to calculate it? Note that the calculator in:

http://www.sadoun.com/Sat/Installati...ion-Angles.htm

Will not give you the actual angle that you can measure with the angle finder. It will only give you the angle in reference to the rotor's journal, which also have unknown elevation itself.

[DruzeTito]

what you are forgetting is that the ku dishes are offset. That means they don't directly point to the satellte signal head on.. but they point a bit lower. For example, I have a fortec 90cm dish.. and according to the specs.. it says it has a 24.62 degree offset. When I have a calculated elevation of 35 when i use the calculator for a fixed dish, I set my dish to that using the elevation scale. Now, I measured where the dish is actually looking at (its real angle) with the johnson meter, and it came out to around 10 degrees. So this exactly corresponds to the offset: 35-24.62 = 10.38.

so Calculated dish elevation - dish offset angle = actual angle of dish.

I guess you have to find out your dish offset angle so you can do what you want.

[shrugy]

Druze, Thank you for the quick and concise explanation. It all makes sense now! I didn't forget that ku dishes have offsets because I didn't know about it in the first place. The thing is, most installation sites and manuals only go with simple instructions to make things easy for the consumer. They don't go any deeper in explaining why certain things are done in certain ways. But glad that there are resources like this board where we can ask questions and get more informative answers.

I looked at my dish and didn't find any part number to tell for sure. It's a Fortec dish that I got from Sadoub couple of years ago. I think it's a 31". It looks precisely like this dish but with the HH100 rotor:

http://www.sadoun.com/Sat/Products/STAB/HH90.h16.jpg

Do you know what's the offset of this dish, and what's the inclination of the HH100 rotor journal?

Now, if the offset is about 24, and the sat is at 46, so you end up pointing to 22 on a fixed installation. Do you need to have a clear line-of-site at 22 or just at 46?

[DruzeTito]

OK.. well for the 80cm fortec dish (31inch).. the offset is 22 degrees.

So if your dish was fixed, increase the elevation of your dish using the angle finder to exactly 46 and that will be what your line of sight should be.. but it would not get your signal because it needs to be 22 degrees lower.

The scale on the dish is compensated for offset so that's why it always works for every satellite you calculate.

Now when we get to motors, iam not sure how it all works out and all of a sudden things start to confuse me like "declination" and etc.. But maybe I will think and research a little more and post my findings.

Besides it would be hard to measure the angle when the motor turns the dish to compensate for skew.. so only your true south area would give accurate readings.

[aegrotatio]

I think it's meaningful to add that many dishes have incorrect elevation markings, anyway. My Winegard 76cm is over 8-degrees off. I don't know if it's due to a non-true feed support arm (would be possible) or what but it's definitely 8-degrees off when I peaked my dish. My mount is perfectly plumb and without a motor installed. In addition I corrected for magnetic north (not that this would matter after peaking the dish...).