SMW OA 1600 dish

A

archive10

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Good questions @st1 !
Not really.... Central LNB is more down and forward in such a way that distance from each LNB's focal point has same distance to it's own "Le point G" on the surface of the dish. In Post #7 I was trying to show (green solid line) all points G connected. Perhaps I was wrong... but I can check that drawing real line on antenna by connecting all real points G. Secondly, edgy LNBs are higher than central LNB, that is because Clarke-belt is not straight but curved from antenna point of view. View attachment 80955
I think this antenna would better work on the equator looking directly up and all satellites seen on one straight line.
I fully understand what you're saying.
I am not (at this time) questioning the height or in/out placement of the LNBs.

What I am curious about is that all your LNBs seem to be aligned on their central axes. That is, all LNBs seems to be pointing roughly in the same direction in space.

(I find this challenging to describe in written text, but here goes:)

However, the mirror is curving left-right, so the central axies (or pointing direction) of the LNBs should be fanned out in a curve too. The LNB central axis should be perpendicular to the arc at any given LNB mounting point. If you look in the manual page in post #32 at the angling of the LNBs, you will see that they are following the arc in the vertical plane.

From your pics, it looks like the "edgy ones" are pointing at an angle to the dish surface. Now this will work, as this is how it works with multi-feed LNB configurations on "normal" paraboloid dishes, but what you effectively have is all LNBs in an increasing off-axis position.

So my question was really in two parts:
1) Are you sure if your LNBs are in the centre of the "virtual dish", or at an off-axis angle (having a somewhat more diffuse signal)?
2) If they are in the centre, shouldn't they be pointing with their main axis strictly perpendicular to the dish surface in the centre of the virtual paraboloid dish?
 
RimaNTSS

RimaNTSS

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Took picture from above. We can see that there is some tendency that each LNB is looking little bit away in direction. BTW, it does not mean I finished with tuning of this antenna. Going to spend more time doing that. But, we all know, nothing and nobody is perfect. :D
 

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RimaNTSS

RimaNTSS

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Moved antenna to the place where 45*E should be receivable. If have time, later than will try to tune 45*E-0,8*W
 

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RimaNTSS

RimaNTSS

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Made 3 additional LNB holders today IMG_20150722_192824 (Custom).jpg and added 2 of them to the antenna IMG_20150722_194247 (Custom).jpg . Next week I will have more INOX pipe-clamps, so will finish antenna tuning to 12 birds.
From antenna's back I do not like rusty things IMG_20150722_201445 (Custom).jpg IMG_20150722_201451 (Custom).jpg . Should change them ASAP! Back-frame is made of 32mm pipe, so I've found in the garage INOX pipe with inner diameter 32mm, will use it to make clamp. IMG_20150722_202129 (Custom).jpg
 
RimaNTSS

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Made some items and replaced by them original rusty things. I think I can go on and replace more mount details to custom-made. Unfortunately I do not have enough material in stock.
 

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RimaNTSS

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It seems easy, just make replica of something...... but it took some time for me today: go to the shop to get needed material, cut in proper sized parts, weld them together, drill some holes (some still to be drilled), and polish everything.
 

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Archived-1

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Some very nice workmanship there Rimants :).
 
RimaNTSS

RimaNTSS

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Final product looks like this. Next week, after I get additional 40mm INOX pipe-clamps, will tune this baby and record levels of signal on all received satellites.
 

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Trust1

Trust1

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1.8 m CM at SMR 1224 + Elev. with 7 lnb changer Ku (lin - circ) - Ka (lin - circ) C (lin - circ)
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Very , very nice Rima :-clap
 
gibertini

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what with you and martin-f your putting the manufacturers to shame
 
RimaNTSS

RimaNTSS

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what with you and martin-f your putting the manufacturers to shame
Do not blame me, blame @martin-f , he is guilty one - bad boy!
 
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RimaNTSS

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I have finally decided to go for 13 LNBs with span from 45*E to 4*W. I also found out that simple washing (does not matter how many times you wash surface of the dish) does not bring much improvements. But, after rubbing surface with school robber it gives much better results (red square) . So, I need 3-4 erasers to finish job.
And, that will take several days to get additional pipe-clamps to have all 13 LNBs installed.
 

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RimaNTSS

RimaNTSS

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Brought home 10x42mm pipe-clamps. Unfortunately they are little bit too big for my project. Of course I can adjust them, but 40mm ones would be better. Also got some 60mm clamps (just in case I need experiment with C-band LNBs). And, finally, made couple of fasteners for antenna... I do not think it is possible now to move antenna around the pole, only together with the pole.
 

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RimaNTSS

RimaNTSS

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Finished installation of LNBs. Used 5 x 42,4mm clamps, do not like them, but another 40mm clamps will arrive only Friday evening. Got OK signals on all LNBs. When rain stops and sky clear up (if so) will do some scans.
 

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a33

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What I am curious about is that all your LNBs seem to be aligned on their central axes. That is, all LNBs seems to be pointing roughly in the same direction in space.
.....
So my question was really in two parts:
1) Are you sure if your LNBs are in the centre of the "virtual dish", or at an off-axis angle (having a somewhat more diffuse signal)?
2) If they are in the centre, shouldn't they be pointing with their main axis strictly perpendicular to the dish surface in the centre of the virtual paraboloid dish?
Took picture from above. We can see that there is some tendency that each LNB is looking little bit away in direction. BTW, it does not mean I finished with tuning of this antenna.
Hi,
I came to this thread following RimaNTSS' picture of the SMW1600, in my thread Multifeed installation and exact calculation of LNB position

As we know a purely toroidal dish is parabolic in het vertical plane, and spheric(or better: circular) in the horizontal plane.
In a circular mirror the length of the radius is two times the focal distance: r = 2 f.
That means the red line in the drawing of RimaNTSS should just go till twice the distance from the dish to the LNBs, that is: just to the centre of the circle. (In his drawing he seems to go more than three times the distance from dish to LNBs; that is much too far!)

toroidal dish RimaNTSS SMW1600.jpg

Aiming of LNBs should ideally follow the (corrected) red line from centre of circle, through LNB, to dish.

However, as the drawings of the manual in an earlier post show: You can aim two or three LNBs with very small azimuth differences towards each other. Placement of the head of the LNB in the phase centre is much much more important than the aiming angle of the LNB! Didn't Paul Wade say so, already? (Or was it some other dish-guru? I'm not quite sure.)

That means the aiming on this picture of RimaNTSS isn't ideal :(. However because he has extended the range of the multifeed bracket, the outer LNBs should of course NOT point mostly outside the dish; there he should aim the LNB a bit more inward...;).

Greetz,
A33
 
A

archive10

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Hi,
Aiming of LNBs should ideally follow the (corrected) red line from centre of circle, through LNB, to dish.
Exactly my point above in post #61.
The thing with the toroidal is that it will work with several angles, but it will probably work best if the line of sight from the LNB is exactly perpendicular to the virtual dish.
 
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rayhan

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Hi everyone,

I'm from India. I've built a torus for myself, just for fun. I got it machined to avoid any deviation from the required shape. I made lnb clamps similar to what RimaNTSS made. I'm looking for only two satellites, ABS2 and GSAT. I'm able to point the dish towards either of the satellites but I'm unable to get signals from both the satellites together.
Do note that I don't have any adjustment available for skewing the dish. The difference in azimuth is 40 degrees and elevation is 8 degrees. I figured a way to compensate for the difference in elevation. Let's say that a dish needs to be pointed at 70 degrees elevation, now if I point the dish to 75 degrees elevation and move the lnb linearly up from it's optimum position, I will be able to receive good enough signals.
I tried applying this elevation phenomena to my torus. I was able to implement it, but only when I try to focus on a single satellite.
If someone could give some suggestions as to how to tune for both the satellites together, I would be very grateful.

Thanks in advance
 
RimaNTSS

RimaNTSS

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Hi @rayhan ! Welcome to forum. Any chance to see some pictures of your dish?
 
RimaNTSS

RimaNTSS

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Interesting @rayhan , tell little bit more how you've made this dish. I would say, that skewing of the dish is necessary to get maximum performance.
 
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