Anobody tried dish array?

[nasko]

For a long time I've been toying with the idea of creating an antenna array.
Although my initial idea wasn't for a satellite dish array I don't see why it couldn't be applied to the satellite TV. Since 18" dishes are relatively easy to find I thought it would be great to setup an array of at least 4 dishes.
I know it is tricky and probably very difficult to align all dishes perfectly but it shouldn't be impossible. Also another advantage of arrays is that it is possible to control the direction of the antenna beam electronically.
If somebody is following the SETI project, instead of using one huge radio telescope like Arecibo in Puerto Rico they are planning to use an array of 350 dishes!
So my question is: if anybody has tried that please share your experience.

Thanks

 

[Mr Tony]

Well
Since there isnt much FTA on an 18" dish (you need at LEAST a 30" dish), it can be done.

It isnt that hard to set them up. I have a dish at 119 (sharing between my FTA for audio and Dish Network account) and a dish at 91 (for the audio on ExpressVu and my ExpressVu account).

 

[nasko]

Maybe my explanation wasn't good.
I'd like to get 4 dishes to work together .i.e. point them to the same satellite and feed them to one receiver through a 4-way splitter.
This way the gain of the resulting antenna should be stronger (I don't dare do the math ) than that of a 30" dish.

 

[WTguy]

I think just about everyone here does that already to an extent. You use a diseqc switch not a splitter to feed 4 antennas to one receiver. I run 3 into my Pansat 330a using a diseqc with 4 inputs.

 

[nasko]

The only thing is that a diseqc switch will eliminate the signal from all the antennas but one which isn't desirable for an antenna array.
What I want is not to switch between antennas but to be able to add the signals from all the antennas so it would have a
better gain than a single antenna. See picture, hopefully that would make it clearer.

 

[TuxCoder]

I think just about everyone here does that already to an extent. You use a diseqc switch not a splitter to feed 4 antennas to one receiver. I run 3 into my Pansat 330a using a diseqc with 4 inputs.

That's still not quite what nasko has in mind. He simply means a "4 eyes are better than one" approach when each individual eye is not quite big enough to see the object by itself. It's a complementary use of multiple dishes rather than the usual supplementary approach. Take 4 18" dishes, point all of them at one satellite, and somehow tie them together (i.e. a simple high frequency splitter) to hopefully combine all 4 weak strengths into one stronger signal strength.

I'm not sure that will work though for a couple reasons. With Ku (FSS) being slightly lower frequencies than DBS, the antenna (reflector) needs to be a certain size to match the wavelength. I don't know if 18" cuts it or not. As for the fact that they are lower power (another reason for the larger dish), and the real issue he's asking about, I'm not sure a splitter combining the 4 inputs will really combine all the input signal sources together to boost them to an acceptable level. You may be right nasko, some evil math may need to be done. But I'm a little skeptical.

 

[TuxCoder]

See picture, hopefully that would make it clearer.

What I see is Casper the friendly ghost playing with a blue beach ball. Analyze me all you want!

 

[nasko]

Tux,
Thanks for helping me clear my point.
The question is not if it's possible to be done but how to do it in home environment. I was reading for one of the satellites that it uses just that kind of antenna type.

Here is the frequency spec for the 18" dish taken from Winegard's web site

Frequency range 10.95-12.75 GHz (the same as the 30" one)

http://www.winegard.com/home/46cm.htm
http://www.winegard.com/home/76cm.htm

 

[Cascade]

An array of passive antennas for frequencies up to 1Ghz is workable and not too difficult to design.
When you're talking about taking 4 LNBs (Each with their own active components) and tying them together electrically to work as one, you're way out of the league of home experimentation.

Although technically it could be done, it's not worth it for what you're trying to achieve.

On the other hand, if you're thinking of using one LNB and having 4 parabola pointing toward it, you'll beed to find an LNB with the proper characteristics.

With Ku (FSS) being slightly lower frequencies than DBS, the antenna (reflector) needs to be a certain size to match the wavelength.

Nah, Anything down to frequencies as low as human speech can be reflected by an 18" dish, the only reason an FSS needs a bigger reflector than a DBS is for lower power and polarity.