focal distance question?

[crimefighter]

Using a 10ft mesh, all other things being equal, which is would be preferred for c/ku combo, a shallow, or a deep dish. I understand the deep dish will require more acurate aiming but are there any other pros or cons to either one. My dish hunting has produces 3 10fts 1 appears to be much deeper then the others. I also aquired a 7.5ft and a 12ft. none of which have a co-rotor. I am still hunting for one of those. If not found soon I may plant one 10ft and put a straight Ku system on it.

 

[Anole]

other factors:

I think a solid or perforated (little round holes punched in metal sheet) would make the better Ku dish.
Likewise, the more accurate parabola would make the better Ku dish.
That might mean a dish which was made by spinning a big sheet of solid or perforated aluminum and pressing it against a form, to make the shape.
(hence the term: spun aluminum)

That doesn't stop other dishes from doing quite well.
From what I've read about his 12' Paraclipse, Stogie seems to have a real Ku signal sucker.
And I believe those panels are perforated.

What I did was find out what dishes or dish-characteristics were most desirable, and then went out and got two.
So, list the specs or brands of what you found/collected.
You might have a real gem, already - :up

 

[pendragon]

One of the problems with deep dishes is finding feeds optimized for the wide illumination angles required. None of the normal FTA C-band or combined C/Ku feeds are properly designed for something on the order of an f/D of 0.28 (my Winegard Pinnacle), although I can pull the scalar ring far enough back on some so it works ok. The danger of a higher f/D feed is it can't 'see' the outer area of a deep dish. This is probably why deep dishes tend to get the label of having lower gain than shallow dishes.

That said, radio astronomers use deep dishes, not for their gain, but for their better signal-to-noise ratio. That's what you need to lock weak signals; gain is meaningless if the noise floor is also high. A shallow dish is much better when you are transmitting and want to radiate as much of the feed's energy in the beam as possible. So technically all things being equal, a properly configured deep dish will out-perform a shallow dish for receive-only whereas the converse is true for transmitting.

So where does that leave you? If you're going to put a corotor C/Ku feed up, I'd probably recommend a deep dish. Corotors normally have a wide adjustment range for f/D. I'm not sure why you would bother with a Ku-only feed on such a large dish. That amount of gain is rarely needed. If you go Ku-only, you will need to get a feedhorn designed for a prime focus dish, because normal Ku feeds are designed for offset dishes with very large f/Ds, much large than even 'shallow' C-band dishes. With a prime-focus KU-only feedhorn, I would go shallow.

I do have a project brewing to modify a combined C/Ku feed (this is a dual ortho feed) to accurately match the Pinnacle. The math says it will have essentially the gain of a typical shallow dish, but the CNR of a deep dish. That remains to be seen.

 

[crimefighter]

Thanks for the responce. For dishes I have a 10ft winegard, 12ft conifer, unimesh 10ft, haul-tronics 10ft (this is the one that seems deeper then the others) 7.5ft "country tv", not sure who actually made it.

In addition I have numerous actuators including a couple of 36in von wiese most are superjack or alike 24s and lots of C band lnbs ranging from 40d down to 17d echostars, cal amp, chapperal, others too.A couple of analog c receivers currently only a pansat 2700a for fta. (that will change if i go fixed Ku, i will add another fta receiver).

I have the pansat on the 10ft unimest, this dish has lots LOTS of hail damage. I still get consistant signal of 80s plus and qualitys that vary greatly but most will lock I ll say they range from 55 to 90.

Now as to why a big bud for Ku?....because I can!...lots of room, lots of dishes, a wife that dont care, and mostly because thats what i have on hand. I have located a couple of prime stars but not had time to try and aquire them.

My location is northwestern Wisconsin. I am about 70 mi northeast of Eau Clare or 70 mi southeast from Duluth Mn. My dish hunting has been easy, even to the point that my last one, the Haul-tronics, that person called me and said "I hear you take down dishes" answer...Yes I do, end of the dealing. All of them have been free. I take anything that comes my way soon I think I will a have a C band junk yard, LOL. The list of dishes is just what I have saved, others were bent, or otherwise junk.

 

[truckracer]

The deeper dish may require a little more tuning compared to that of a smaller one.
Ku has to be pretty exact on a large dish. My 10' sami screams on ku using a chapparall dual c dual ku feed horn.
I have Norsat KU lnbs and cheapo c-band lnbs. the norsats came with the feedhorn from ebay.

You should be quite pleased with the larger dish.
I have a 7.5 that performs almost as well as the 10' My 10 really blows my 7.5' on ku....strange isn't it...you would think it would n't matter as much on large reflectors.

the 10 yields slightly better signal than the 7.5

 

[crimefighter]

Thanks truckracer for your input, think I might actually use the 7.5ft I have for strickly Ku. For moving the dishes I have a Uniden UST710 controller? I have used this box for many years prior to switching to a programmable c band reciever. The UST710 is strickly a manually activated control but a i really like it because its simple and I can bumb it sometimes even just half a degree. I orginally had a very simple/basic Uniden C band reciever too but it burned up on me. If I use the pansat as the sole reciever I should still be able to find the sats but watching the signal strenght and bumping the dish accordingly. Saduon has a Ku lnb listed that is 50mm in diameter. I have an adjustible scaler ring mount that I am pretty sure will accept it with no problems. Any thoughts on not using analog c band to move and find the sats?