OTHER Help With dish alignment.

[Codematic]

Greetings,

I have a surplus AVL 1278 Mobile VSAT antenna that I am trying to get a signal with. Its a 1.2 meter reflector, with an "Offset, Prime Focus" have an EPS-020 LNB on it.

I *think* I have it pointed correctly, but not sure on where to measure the angle from. Should I measure the angle from the exact center of the Dish face ? or Is it from the boom angle ?

Total NOOB here, but have been trying to get it working with a new Amiko HD-265 for two days. I get absolutely nothing, 0% on the level meter, with quality at 6% with the cable disconnected. I'm trying to catch Galaxy 16, since it "seemed" easy...

I must be missing something fundamental here.

Thanks Again,

 

[mr_rye89]

That’s a funky dish. Is there any published info on the LNB/F? Is it an uplink dish with a transmitter? Might be as simple as the local oscillator frequency being wrong on the receiver. My 1 meter Hughesnet dish with its stock LNB worked at 10760 mhz just like a standard Ku LNBF. Maybe your hooked to the transmitter instead of the receiver LNB?

 

[arlo]

Maybe this will help. 22-25 degrees is usually the elevation or there abouts. I'm guessing that means if the angle of the dish face was parallel to the horizon, the look angle would be ~22 degrees higher.

Finding dish elevation offset angle.

 

[a33]

To add to the above:

When the dish face is in fact flat ( a string from top to bottom across the dish barely touches a string from left to right ), then the offset angle can be calculated indeed by cos(offsetangle) = width / height (width and height measured on the working (parabolic) area of the dish, so without the rim).
When it is non-flat, two extra measurements (of the depth at the center) are needed.

For Boston, elevation for 99W is 33.5.
Subtract the calculated offset angle from it, and you have the needed elevation angle of the dish face for the correct elevation aiming.


I'd be curious to the proper LO-frequency(ies?) as well.
Frequency range would be 10.95 – 12.75 GHz, according to specs.

https://satcom-services.com/products/avl-technologies/avl-technologies-121-model-1-2m-1278fd-mobile-vsat-fly-drive-antenna.pdf

Greetz,
A33

 

[Codematic]

That’s a funky dish. Is there any published info on the LNB/F? Is it an uplink dish with a transmitter? Might be as simple as the local oscillator frequency being wrong on the receiver. My 1 meter Hughesnet dish with its stock LNB worked at 10760 mhz just like a standard Ku LNBF. Maybe your hooked to the transmitter instead of the receiver LNB?

I am using an EPS-020 LNB, I'm pretty sure its in the right place. The BUC can only connect via is flexguide in one place. Although I've been leaving the BUC off. I think I'll put it back on, even if its not powered on.

There really isn't another place to put the LNB,
I confirmed the LNB in a previous post.

Thanks for the reply,

 

[arlo]

Maybe this will help. 22-25 degrees is usually the elevation or there abouts. I'm guessing that means if the angle of the dish face was parallel to the horizon, the look angle would be ~22 degrees higher.

Finding dish elevation offset angle.

I'm interested to see what you're using for the controller to move it.
Yeah. The whole trigonometry thing is definitely probably the most accurate way to calculate the reflection angle.
I just like the method I linked to and also chunks of aluminum foil around the rim and aim it at the sun with a paper target at the feed throat. Someplace I ran across a guy who sprayed the dish surface with soapy water and stuck a piece of 'space blanket' from wally world to it like window tint.
Once you get the sun angle figured out (the web will give you that for your location).
And then a straight edge from top to bottom of the dish, a protractor. I use a slick digital level.
A bit of phone calculator or good old pen and paper.
There you have it. At least a close ballpark.

Here's a manual I grabbed. Not much on the geometry particulars but very interesting stuff.

 

[primestar31]

I am using an EPS-020 LNB, I'm pretty sure its in the right place. The BUC can only connect via is flexguide in one place. Although I've been leaving the BUC off. I think I'll put it back on, even if its not powered on.

There really isn't another place to put the LNB,
I confirmed the LNB in a previous post.

Thanks for the reply,

You do know that lnb is only a single polarity, either Vertical OR Horizontal, depending on how it's mounted. IF it's mounted to the waveguide for horizontal for instance, yet your receiver is trying to scan in Vertical channels, you won't get signal.

 

[Codematic]

Maybe this will help. 22-25 degrees is usually the elevation or there abouts. I'm guessing that means if the angle of the dish face was parallel to the horizon, the look angle would be ~22 degrees higher.

Finding dish elevation offset angle.

The dish actually has dimples right at the edges of the dish at top/bottom, left/right. So measuring those, I get 49.75in, and 47.5in with 3.5in depth.

Using the linked site, I get 17.3 deg offset, and a 0.81 F/D. Interestingly the F/D calculation is the same as the AVL specs call out. So I think I have it correct now.

Thanks for the info !

 

[Codematic]

You do know that lnb is only a single polarity, either Vertical OR Horizontal, depending on how it's mounted. IF it's mounted to the waveguide for horizontal for instance, yet your receiver is trying to scan in Vertical channels, you won't get signal.

I have heard that. I can control the skew with a motor, supposedly it goes +-95 deg. I think I could overcome the limitation with that ?

Thanks.

 

[Codematic]

I'm interested to see what you're using for the controller to move it.
Yeah. The whole trigonometry thing is definitely probably the most accurate way to calculate the reflection angle.
I just like the method I linked to and also chunks of aluminum foil around the rim and aim it at the sun with a paper target at the feed throat. Someplace I ran across a guy who sprayed the dish surface with soapy water and stuck a piece of 'space blanket' from wally world to it like window tint.
Once you get the sun angle figured out (the web will give you that for your location).
And then a straight edge from top to bottom of the dish, a protractor. I use a slick digital level.
A bit of phone calculator or good old pen and paper.
There you have it. At least a close ballpark.

Here's a manual I grabbed. Not much on the geometry particulars but very interesting stuff.

I agree, I definitely need the math to work. I detailed the calculations in another reply here.

 

[Codematic]

That’s a funky dish. Is there any published info on the LNB/F? Is it an uplink dish with a transmitter? Might be as simple as the local oscillator frequency being wrong on the receiver. My 1 meter Hughesnet dish with its stock LNB worked at 10760 mhz just like a standard Ku LNBF. Maybe your hooked to the transmitter instead of the receiver LNB?

The LNB I am using isn't the one that came with it, I asked about it specifically in a previous post. Its an EPS-020, which should work at 10750... but we shall see.

Thanks!

 

[Codematic]

I'm interested to see what you're using for the controller to move it.
Yeah. The whole trigonometry thing is definitely probably the most accurate way to calculate the reflection angle.
I just like the method I linked to and also chunks of aluminum foil around the rim and aim it at the sun with a paper target at the feed throat. Someplace I ran across a guy who sprayed the dish surface with soapy water and stuck a piece of 'space blanket' from wally world to it like window tint.
Once you get the sun angle figured out (the web will give you that for your location).
And then a straight edge from top to bottom of the dish, a protractor. I use a slick digital level.
A bit of phone calculator or good old pen and paper.
There you have it. At least a close ballpark.

Here's a manual I grabbed. Not much on the geometry particulars but very interesting stuff.

The mechanical parts of the dish are solid, the electronics not so much. Although the sensors, limit switches and motors themselves are fine. Some of the wiring, and connectors are roached, so I've replaced the ones that needed it. I have a embedded systems, and motor control background, so I'm putting together a board that controls it.

I am going through the manual process of aligning the dish so that I understand it. Having fancy sensors doesn't mean jack if I dont know how the thing works.

Thanks for the insight,

 

[arlo]

The mechanical parts of the dish are solid, the electronics not so much. Although the sensors, limit switches and motors themselves are fine. Some of the wiring, and connectors are roached, so I've replaced the ones that needed it. I have a embedded systems, and motor control background, so I'm putting together a board that controls it.

I am going through the manual process of aligning the dish so that I understand it. Having fancy sensors doesn't mean jack if I dont know how the thing works.

Thanks for the insight,

Sounds like a cool Arduino project.
In the manual I see the X-Y and polarity sensors are all pots. Things that Arduino and other kits would play nice with.

 

[a33]

The dish actually has dimples right at the edges of the dish at top/bottom, left/right. So measuring those, I get 49.75in, and 47.5in with 3.5in depth.

Using the linked site, I get 17.3 deg offset, and a 0.81 F/D. Interestingly the F/D calculation is the same as the AVL specs call out. So I think I have it correct now.

Thanks for the info !

View attachment 156145

NB! Topstring and bottomstring are calculated incorrectly at satsig (as is posted at several other locations on the internet)!

In your case, they should be 1350.43 and 975.28 (so the bottomstring value is very near...).
Is the LNB presently about at that location?
( NB I've seen a VSAT dish, where the calculated offset angle was very much doubted. At that time, I didn't have a standardised calculation method to calculate the offset angle from multiple depth measures along the vertical center line of the dish, so we didn't determine the cause. [Edit: it could have been an incorrect parabolic shape?]
If needed, I have the equations now ready (though not yet in a spreadsheet calculator...)

The subtended angle of the dish towards the focal point with these values is 63.4 degree ( f/D-equivalent 0.88 ).

BTW If you input the inches values in satsig, you get the outputs also in inches (though the indication still says mm).
Degrees stay degrees, ratio stays ratio......

Greetz,
A33

 

[Codematic]

Sounds like a cool Arduino project.
In the manual I see the X-Y and polarity sensors are all pots. Things that Arduino and other kits would play nice with.

Yup have the boom controls working already.

 

[Codematic]

NB! Topstring and bottomstring are calculated incorrectly at satsig (as is posted at several other locations on the internet)!

In your case, they should be 1350.43 and 975.28 (so the bottomstring value is very near...).
Is the LNB presently about at that location?
( NB I've seen a VSAT dish, where the calculated offset angle was very much doubted. At that time, I didn't have a standardised calculation method to calculate the offset angle from multiple depth measures along the vertical center line of the dish, so we didn't determine the cause. [Edit: it could have been an incorrect parabolic shape?]
If needed, I have the equations now ready (though not yet in a spreadsheet calculator...)

The subtended angle of the dish towards the focal point with these values is 63.4 degree ( f/D-equivalent 0.88 ).

BTW If you input the inches values in satsig, you get the outputs also in inches (though the indication still says mm).
Degrees stay degrees, ratio stays ratio......

Greetz,
A33

Ok. Curious what you mean, I get the calculation is off. But your saying the offset angle is 63.4 and not 17.3 ?

Thanks,

 

[a33]

No, the 63.4 is the needed illumination angle for the LNB feedhorn!
That means a normal LNBf (for an offset dish) would look partly over the sides of this dish.

The offset angle is 17.3, allright.

Edit: Sorry, forgot that you are new to this. Should I have explained the terms more clearly?
With the offset angle, you can now try the proper elevation angle for the dish?

The topstring and bottomstring lengths are used, to check the location of the LNB feedhorn: the distance to the top, and the distance to the bottom of the dish.

Greetz,
A33

 

[Codematic]

No, the 63.4 is the needed illumination angle for the LNB feedhorn!
That means a normal LNBf (for an offset dish) would look partly over the sides of this dish.

The offset angle is 17.3, allright.

Edit: Sorry, forgot that you are new to this. Should I have explained the terms more clearly?
With the offset angle, you can now try the proper elevation angle for the dish?

The topstring and bottomstring lengths are used, to check the location of the LNB feedhorn: the distance to the top, and the distance to the bottom of the dish.

Greetz,
A33

Oh, ok. Thanks for the clarification.

No worries. Yes, new at the satellite thing. I have experience with Amateur radio stuff, but nothing with a dish. Just trying to discover what I dont know at the moment.

I'll give it another try when the rain stops here.

Thanks so much,

 

[Codematic]

I GOT SOMETHING !
Not sure what satellite it is... but its something !
I have been trying to aim for Galaxy 16, I dont see video from them though.

Thanks for the help everyone.

 

[a33]

Is that 91.1W ( 12224 R 20000) ?

Bell TV on Nimiq 6 at 91.1°W - LyngSat