Project Four Leaf Clover (1 Viewer)

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Trust

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Jun 1, 2011
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Nijmegen Netherlands
More than once I've seen the question passing by , is it possible to connect two dishes together to get more signal from one satellite .
I know to connect two out-ports from two lnb's is almost impossible for amateurs like us by the uneven synchronisation of the LOF's , but maybe , if you can connect the wave guides together , it might be work .

So two weeks ago I started with 2 Triax TDS64 dishes , set to zero elevation .
For that I have to cut a part of the poleclamp .
Those dishes have a offset of 26º
zero elev.jpg

Than attached them opposit at a tube to find the angle between the feedhorns with enough room for 2 more feedarms .

angle set-up.jpg



Now I could make the quatro-feed and 4 long neck feedhorns .
The shape of the feedhorns are not all the same , could be a issiue to solve later .

quatro feed.jpg



To let look it like a four leaf clover , I made a cross pole at a temporary stand with a fine elevation adjuster , later I noticed thats a bad idea since each dish must be optimised single .
Thats easier to do when they are horizontal or vertical .

elev adjuster.jpg



Pointed the set to Astra 19.2º E and found a high signal ( S 60% ) at 10744 H but with bad quality ( 28% ) , but it still gives me a picture .
I do have a Clarketech Combo satmeter , that connected to my 1.2 M Fibo gregorian dish , shows 55% S on that TP with a Q of 54%

four leaf clover.jpg




As you can see there where bad weather conditions and I run out of time that day no chance to tweak each dish . There I stopped .

To set each dish to the optimum , I gonna turn the cross to upright .
When each dish is proper set I want to remove the feedarms and replace them for a tube from the centre off the cross to the centre bolt at the quatro feed .

Today I finished some changes , made a 25 mm diameter bar through the centre of the cross fitting in a gearbox .
The gearbox is on top of the modded poleclamp and can be turned by a hand to turn each dish on top .
Also had to make a new elevation fine adjuster .
Now the quattro-feed is also connected by a M10 threaded rod to the top of the 25 mm bar .

gear cross.jpg

feed at bar.jpg


If I find the time tomorrow I will attach the other dishes and test again .
 

Titanium

AI6US
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May 23, 2013
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Does the signal quality increase or decrease as each feedhorn is covered? The cavity where the waveguides merge must be tuned to present the LNBF with in-phase signals. Likely severe cross polarity issues as well.

A group of radio astronomer hobbyists have had success combining multiple dishes using our PLL LNBFs. They are disabling the internal crystals and injecting the reference frequency from an external generator using matching length coax cables.
 

Cham

VE4GLS
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Dec 19, 2008
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Figuring out the phasing system for this project begets an excedrin headache... at least for me. One millimeter difference on reflector distance to the feedhorn can displace 2-3dB of signal. Times that by 4 for the different reflectors, and the feedhorn to waveguide interface...

Basically by adding another 3 reflectors you are multiplying the reflector surface area, and offset dishes are basically a portion of a prime focus reflector parabola. I would think using one feedhorn pointing at the center would likely more than compensate for feed/waveguide losses. Just need to adjust for focal depth of the assembly, which would be 50% of what one dish would represent if you calculate the total width and depth of the assembly. Using a prime focus scaler would help too.

Adding mesh/screen behind the assembly would help block ground/terrestrial interference seeping in between the "pedals" and help improve S/N as well.

Just my 1 1/2 cents. (definately not worth 2 cents). :)
 
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Trust

Thread Starter
SatelliteGuys Guru
Jun 1, 2011
131
154
Nijmegen Netherlands
Since the quattro feed is now at the bar , I can remove the feedarms .
Once there is a reasonble signal , testing with a pf lnb (flat scalaring) was already my goal .
I was aware from the noise coming through the openings .
The setup above is only a start and a way to kill my free time and keep me (us) occupied .
 

Trust

Thread Starter
SatelliteGuys Guru
Jun 1, 2011
131
154
Nijmegen Netherlands
I forgot to rapport my progress findings at this board , the quattro feed was the most critical part .
With two feedhorns opposit and closing the other openings there was a little increase versus a single Triax TDS64 dish .
But with all four feedhorns I lost a lot of signal .
So I stopped this project and dismanteled the structure , but kept the avatar .
 
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wvman

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Sep 19, 2014
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N. Central WV
Since the quattro feed is now at the bar , I can remove the feedarms .
Once there is a reasonble signal , testing with a pf lnb (flat scalaring) was already my goal .
I was aware from the noise coming through the openings .
The setup above is only a start and a way to kill my free time and keep me (us) occupied .

One hell of an interesting project, but not something I would tackle, given the fact that I don't have the engineering expertise to do such projects. I did once upon a time, take a Unimesh 10 foot dish, remove the screen, saving it of course, and cut aluminum panels out of flat sheet metal used to make gutters, and replaced the wire mesh with these panels. Luckily, I had a friend with a metal shear that made the cutting process much easier.

The screen wasn't in the best shape, so I figured I had nothing to lose by doing it. It turned out to be a stellar idea that worked great. The dish was actually hooked up before starting this project, so I noted the signal level. Noted it again after installing the new panels and got a signal level 46% higher than the wire mesh. It also worked like a champ on Ku. Then disaster struck. Had a really bad storm the next summer that resulted in a tree being uprooted that took out the dish.

I have a 7 1/2 foot dish just like it that has damage to the screens and I've been considering the same thing with it. It's kind of a pain in the butt since Unimesh saw fit to have their screen slide onto slots along the inside edge of the ribs, and then welded a piece of aluminum L channel along the outside edge of the dish, blocking the removal of the screen by sliding it out. It also makes it difficult to put screens back in track if they're punched out. In order to correct this problem, it becomes necessary to remove about a quarter inch of the lip along the outside of the dish.

Like yours, it was one of those projects I worked on in my spare time.
 
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