Coupling two 1.80m dishes as one 3.60m dish

al_madhi

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#1
Hi ppl , wondering Is it possible to couple two 1.8m dishes to act as if it is one 3.6m dish by connecting the outputs of the two 1.8m dishes through a combiner switch ( two in & one out ) providing the two 1.8m dishes are aimed at the same satellite which requires 3.6m in order to receive it in the fringe reception area .
Any thought you would have be greatly appreciated .

cheers
 

Likvid

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#2
Not working any good in Ku-band, in C-band it can work pretty good, but it isn't like coupling two 5 meters dishes and think you get 10 meter, it's more like 7.5 meter in reality.

Dr.Dish had an artice about this long time ago, you may contact him for further info.
 

rolfw

Believe it when I see it Admin.
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#3
There are also a couple of long threads in the archiive here regarding the technical details of such a project, it was found that to do it effectively would be so expensive and with such small gain, that it would be impractical. It is not simply a case of combining the two signals,from memory you would need perfectly matching waveguides and specialist LNBs.
 

Lancelot

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#4
Is there still nothing within easy reach, that could Phase Compensate one of the LNB O/Ps .

Rolf. ??


L.
 

rolfw

Believe it when I see it Admin.
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#5
Not as far as I can remember, will try and search for the thread, but the potential gains were far outweighed by the cost, well out of reach of even the wealthy hobbyist.
 

Lancelot

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#7
Thanks for that Rolf -
Interesting reading. I was relying on a locked O/P
But as we see, the mech solution is expensive and so it would seem was the electronic version. Just wondered if the electornic fiddle was within easier reach now. But probably not. :)


L.
 

Channel Hopper

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#8
If you have time, a good background in software programming, and a modern PC with the right processing software, you should have no problem.
 

ouagadougou

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#9
Hi all,

I recently found this forum so hello everyone. I noticed that you have quite a few threads running that are of a detailed technical nature :) and a few things occurred to me regarding this thread in particular.

RF Combining (Pre LN:cool: - you are likely to achieve less than 2.8dB of extra gain from RF Combining 2 dishes of the same size due to the overall collecting area of the 2 dishes and the added losses of the combining network waveguides, connectors and combiners. It would be better to just have 1 new reflector with the same area as the 2 proposed dishes combined, this should give an extra 3dB. Does anyone have any practical results from RF combining 2 dishes ??

IF Combining (Post LN:cool: - this gets quite difficult and requires each lnb to be phase locked to the same frequency plus delays between the 2 IF paths have to be compensated. Exactly how much gain you would get in a system working in real time is very debateable and is unlikely to be better than the 3dB mentioned above unless you can apply some mathematical manipulation of the IF signals. Does anyone have any practical experience of IF combining ??

Interferometry - not sure this will work either as it relies on the earths motion to some extent to allow aperture synthesis when observing a distant source and we wouldnt have this relevant motion when observing an earth satellite as its motion is limited by its position in the Clarke Belt. Real Time Correlation could also be an issue. Does anyone have any practical experience of Realtime Correlation of broadcast type signals or the use of Interferometry for near earth orbiting objects like a satellite ??

Diversity combining - digital microwave links use 2 antennas with diversity switching but the diversity switch selects the best of 2 signals from 2 antennas and doesnt actually do any adding or actual combining of the 2 signals in real time.

Just a few ideas and questions. Personally I am considering building a 4m offset reflector for simultaneous use on multiple frequency bands (Ku/C/Amatuer) as a test case before looking at a final dish size of 6 to 8m homemade. I have 5 surplus 2m Prime Focus Dishes at the moment which would make a great array if I was convinced that combining them would be worth it !! :confused .

Cool forum guys.

Cheers.
 
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