Upside Down or Inverted Dish Installation.

[Anole]

Adrian -

As stated above, you don't generally mix an inverted dish with a motor.
Part of the reason is because the motors do not work for birds so close to the horizon.
They just do not have the tracking range.
Motors operate with reduced accuracy as they approach the horizon.
So, the way to receive satellites near the horizon is to use fixed dishes.
Over the supported operating range of any given motor, you do not need to invert the dish.

 

[adrian]

Anole i have noted and respect your reply.As i have done all the changes as outlined in my previous post and having gone so far, i at least would like the satisfaction of tracking some of the satellites with an inverted dish.Could you or someone else please advise me on the mathematics.Thanks.

 

[SatPhreak]

I've mounted a dish upside down, but it was to give enough head room while walking underneath it. It was only a fixed dish that skewed. Once it was aimed at the sat I wanted, I just skewed the dish 180 degrees in order to walk under the arm for the lnb instead of it hitting my head if I walked under it. Once it was upside down I've aimed it at several sats but since the elevation scale on my dish was still right side up I could just set the elevation scale to the proper number. Without trying to think about the modified elevation scale if was inverted also, I think mikekohl gave the right way to figure it out.

 

[Smith P.]

No it's not the same here in Puerto Rico they do that crap when they installed me the Dish Network system they put 110 sat upside down but I asked them to fix it I live in a clear area with no mountains surronding me I have had something blocking the area we then you could put it upside down.

Totally untrue - if you have no LOS, the upside down dish will never help you !

 

[mikelib]

I thought about the inverted dish for two days. I was looking at web sites for trigonometry and geometry to try and figure out the angle of elevation of an inverted dish. I had in my head that the dish can be treated as a right triangle where one angle would be 90 degrees, the other angle stated would be 12 degree since all angles in a right triangle has to equal 180 degrees then the inverted angle would be 78 degrees.

Then I had another thought, all you have to do is set up the dish using the information from dishpointer elevation, skew, etc. and take the nuts and bolts off the dish face plate that hold it to the elevation and skew control plate and turn the dish upside down and bolt it back to the elevation and skew control plate. You now have an inverted dish with the correct elevation and skew. I think this works and might try it this weekend.

I have been trying to get the White Springs Channel on Galaxy 129 west for a while now since I can get AMC 21 at 125 west OK. My problem is that I don’t have a clear line of site west at that elevation. But I keep trying. With my motorized system I get almost all of the satellites from 15 west to 125 west.
Mike Lib

 

[Anole]

all dishes not created equal:

Depends on how the dish and mount are built.

Some dishes which are on skewable mounts, can be rotated upside down.
(even if you have to remove/replace some bolts to do so)
For these dishes, and the DirecPC in particular, the elevation scale reads correctly either way.
(thanks go to a clever observation by Tron last year, on the subject)

On other dishes you cannot assemble it to its mount but one way.
Often, the LNB holder and arm, are part of the mount, not part of the dish.
In that case, you must rotate the entire dish and mount upside down.
For these dishes (I'd assume Fortec Star and similar) the elevation scale reads backwards, and there is a fixed offset.
That makes figuring out where to set the dish on its elevation scale, a bit tricky.

 

[DishDigger]

I have a sat motor tracking the Clark belt with the Apex satellite being at 49 degrees at true north in Africa.To enable me to view a satellite which is low on the horizon i will have to turn the dish upside down.For the dish to move freely by way of elevation i had to turn the sat motor up side down as well and modify the elevation setting plates. The sat motor arm is now pointing upwards instead of down.I am lost on the mathematics of how to determine at what reading the Apex satellite will be.(my dish has a built in offset of 22 degrees)Can someone please help.

I won't be a lot of help, I've been working with angles, etc. most of the afternoon here on an UPRIGHT dish, however, I might caution that the east and west motions for the motor will be reversed if you invert the motor -- something else to think about...

 

[SatPhreak]

East and west would be backwards if the motor is installed up side down, but by changing your latitude in USALS setup from S to N would get it to go the correct way.

 

[Mr Tony]

never thought about inverting the motor...

 

[DishDigger]

East and west would be backwards if the motor is installed up side down, but by changing your latitude in USALS setup from S to N would get it to go the correct way.

Why didn't I think of that ? I guess that's why more than one person can participate . I probably would have found a way to fasten the post that was supposed to go to the dish onto the support post and mount the dish where the post was to go . I never claimed to be real bright - ha....

 

[zamar23]

The only real reason to invert a dish is to avoid mechanical problems caused by a normal antenna having a true reflector elevation angle of less than zero / straight up vertical when incoming elevation is less than 22 degrees. Inverting the dish will point the reflector physically somewhere between 25 and 50 degrees in most locations, reducing the amount of atmospheric ground noise received when pointing at or below the horizon. This is usually a minor issue that is often beat out by the increase of problems caused when the reflector is pitched above a 45 degree elevation...causing rain to pool on the dish during downpours and killing the signals immediately.

Other reasons to invert a dish may be restricted space to mount it vertically, or to avoid part of the dish shadowed by an obstruction to signal in regular vertical position. In last scenario its possible to gain noticeable signal Q raise by inverting the dish.

 

[guapoharry]

Think about it... For a dish motor like SG2100, if the motor were mounted up side down, would the declination work correctly?

 

[Anole]

yes, I think so:

The real "declination" is provided by how you adjust the dish's mount on the motor.
If you were to invert the motor, you would have to invert both the motor and its mounting bracket.
Then, the markings would be no more suitable, than the ones on the dish's mount:

For these dishes (...) the elevation scale reads backwards, and there is a fixed offset.

I'm not saying -anything- about how to read the motor's bracket, though! -
. . . assuming it even has sufficient range . . .