big Ku feedhorn ?

[Anole]

The 6' Andrew/ChannelMaster Ku feedhorn below, obviously matches the dish.
On 6' Prodelin dishes, the Ku transmit/receive module has a big feedhorn. (pix by Corrado)

In recent threads, Magic Static, Tech#344, and Pendragon, have modified regular DBS feedhorns to fit the DishNetwork FSS LNB.
These all provide better performance than the 105° feed which was the only stock alternative.

So, when I was looking at some dishes on an apartment building, I noticed one of the LNBs on a DirecTV dish had a large feedhorn.
It is built by several suppliers, and below there are pictures of two.
Note the oversize 119° feedhorn.
I was wondering if it might be adapted to our use in FTA, perhaps giving better performance on a 1.2m or even 1.8m dish, should we be unable to locate the proper one?

All opinions are welcome.

 

[Magic Static]

I've been wondering about one design aspect in these feedhorns. A lot of the circular DBS horns have a blade in them. The 121 SuperDish Circular side does not. It does have a set of parallel flat sides positioned at 45°. Does this accomplish similar bias? Notice the "Positional" 105 feedhorn has these sides. Of course these would change alignment when twisted. Does help circular polarization or reduce linear interferance?

 

[Anole]

I think it either leaves linear alone (sides vertical)
Or it converts circular to linear (sides at an angle)

Think I posted about this once (from material I learned on the forum).
Let me see if I can find and add it here...

edit:
Normally I like to find an old post with pictures, instead of uploading a picture again.
However, these are very small.
And they are labeled as to their function.
Of course, if you twist to 45° the wrong way, then you won't get Right circular when you select Horizontal polarization, as you should.
105° feedhorn:

 

[Magic Static]

Interesting setup that 105° LNB. what would they do with it in circular mode? ANIK F3? Which really doesn't make sense.

 

[Anole]

I'd really like to know, too.
My guess is they didn't know when the hardware was pre-ordered, whether they could get approval for circular.
Which I assume would have been their preference (?)

And why would I think that (other than circular is uncritical on skew)?
(With a multi-LNB dish, skew really just aligns the feedhorns with the satellites.) -
Well, somehow they got authorization to run circular on 118°, right next door to 119° !
Only way the LNBF can distinguish between the two birds is, the LO for 119° is 11250, and the LO for 118° is 10750! -
Plus, I'm also guessing that processing -both- circular and linear through the one LNB would have been a major plumbing nightmare!

 

[Magic Static]

Thinking about your original question....That LNB is in current use and I doubt DTV will let very many out of it's control. and to buy one just to tear it apart?
That said, there should be thousands of damaged ones headed for the dump in tornado alley. So if you know someone that has access to the junk ones you might find something to experiment with. I will keep an eye out around here for other possibilities.