Ganging multiple dishes for a single bird.

[reamus]

Alright, I'm relatively sure that this question has been answered somewhere, if not on the site, then on the internet in general, however after more hours of searching than I'm really comfortable admitting to, I'm unable to find it, so I'll go ahead and ask anew.

I live in...shall we say, a geographically remote area with adverse conditions for satellite reception.

My original install was a 1.8M dish with a dual LNB pointed only at 101W feeding into a R22-100, and it worked reasonably well. (Current transponder reception grid at the bottom of the post.)

The problem is that it doesn't receive some channels I'm subscribed to, and others are a little touchy ("Oh, look, a cloud! We just lost 12 channels."). Believe me, it still superior to the alternative.

But I got to thinking, I have a 1.2M dish left over from my thankfully now defunct VSAT system, and I was pondering the notion of mounting a DBS dual LNB on it, and swinging it around to point at 101W (It actually has a better line of sight to 101W than my primary dish does, but sadly the post is is little anemic for the 1.2M, and I definitely don't want to try my luck with the 1.8M on it.), then running one line from each dish through a diplexer into each of the tuners on my R22.

There are two questions that this creates for me:

First and foremost: I can't seem to find the appropriate math to tell me whether this is even worth my time as far as improved signal quality goes, can anyone help me out here? The only reference I can find suggests that an array of nine 1M dishes is the equivalent of a single 3M dish, but that was specifically referring to radio astronomy, and while I assume the principles transfer to DBS, I'm not certain.

Second: Do I need to look for amplified diplexers, or diplexers specifically designated for DBS, or will a standard diplexer work acceptably for the task (The last I can source locally, the first two would have to come off the internet and getting things shipped here is...an experience.)

(Current signal strengths are as follows, current weather conditions are a little sub-optimal right now, nominally these numbers are +3 to 5)

88 80 60 00 87 59 59 60
88 82 51 00 89 60 53 61
88 00 51 00 89 58 51 52
88 00 00 00 90 61 00 62

Thanks for any help you might be able to give me.

[Edit 0627h GMT -7 25MAR2009]: Sorry, I just realized that there is technical discussion sub-forum which would have been more appropriate for this, since I can't seem to move the post on my own, rather than cross posting I'll leave it here and hope a mod will move it for me. Thanks.

 

[mental1]

If the 1.2m dish has a good LOS for the 101, why not just get an 18" dish and swap it out for the 1.2m and be done with it? There are pole adapters available if the current poles diameter is too big for a standard 18" dish. Maybe I'm missing something, but that would be the easiest way to do it from what you described.

 

[reamus]

Sadly, 18" won't provide the kind of gain I need to pull a decent signal.

Hence the reason I had bought the 1.8M in the first place...and as it turns out should have bought a 2.4M...but I couldn't afford a 2.4M (And, for that matter, still can't.).

 

[Bob Nielsen]

Combining multiple dishes is not for the faint-of-heart. It can be made to work, but is very sensitive to cable lengths between the dishes and combiner and you could easily be left with less signal. You didn't say how long a cable you have from your 1.8m dish is, but if it is fairly long, you could reduce loss (pick up a bit more signal) by using RG-11 cable instead of RG-6.

 

[oldford]

While it might be technically possible, when you consider the block down conversion and polarity switching that goes on in a single LNB, it becomes a land of unknown. If you had LNA's and could feed the in-phase signals from 2 dishes into a block down converter, you might see some gain, but then you'd lose the voltage controlled polarity switching. And the gain wouldn't be much. for instance: two 1.8m dishes would only have about 3 dB gain over a single dish and that neglects cable/connector/combiner losses, which should not be done at downlink frequencys.
Now that I've typed that and thought about it, I would not even try it. By far, the best way to get more gain is to get the largest dish you can. a 10 footer would be nice.

Good Luck, Eric