OFFSET DISH ON AN “ALT-AZ” MOUNT

[Flinthill]

I have recently mounted a 1.2m GeoSat offset dish on an “Alt-Az” mount (in astronomy this is what we call a mount that moves strictly in latitude and longitude). The problem I’m having is getting the dish to acquire a strong signal in any position except due south.

As I move the dish east or west (Az) I also adjust the latitude (Alt) adjustment in order to track the Clarke belt but the signal strength is very low compared to due south. My plan is to lock the dish on AMC 19 once it is aimed properly. I have the same dish and lnbf on a DG-380 and it works perfectly. Any suggestions about what I’m doing wrong??

Flinthill

 

[phlatwound]

If everything else is the same and working properly (dish, LNBF, cables, connections, receiver, etc.) I would think you are just not aimed properly, the mount type should not be a factor. Possible dish warpage, LNBF placement/focus issues? Also, what is AMC 19, is that a mis-type?

 

[Flinthill]

Sorry, I meant AMC 21. Brain cramp!!!

 

[Hindu55]

Are you adjusting the skew also as you move off south?

 

[Flinthill]

I have rotated the lnbf in both directions from center as I move the dish east and west. This seems to improve the signal strength slightly but not enough to bring in a viewable signal. I don't know how much it is suppose to rotate from a center position when I move the dish west from 101.0 W to the new position of 125.0 W.

 

[Hindu55]

Try here: Satellite Finder / Dish Pointing Calculator with Google Maps | DishPointer.com
Enter your coordinates and pick your Sat and it will give the required skew.

 

[Flinthill]

HINDU55
Now that is a great site!! The first thing I noticed is the need to set the skew to 34 deg. The calibration scale on the Invacom lnbf only goes to 30 deg so I imagined there would be no need to even turn it that far. Now I can see I was not adjusting it far enough. I look forward to giving this a try tomorrow afternoon, providing the weather is decent. Thanks for the site recommendation!!!

 

[Anole]

Yea, that mount is the worst possible solution for a satellite guy.
Three adjustments to make.!.
Once a dish is aligned on a proper polar mount, one movement (motor) ...
- gets you from one sat to the next,
- adjusts your elevation,
- and your skew
...all at the same time. -

 

[Cadsulfide]

SantAnole, you're back!!!!!!!!!!!!!!!!!!!!!!!!!!