KU, C BANDSTACKED LNB COMBO

[kodaz]

This combo begged to be tried because all the parts just fit with minimal work.
these are an FSS and a B1sat stacked lnb.
The hole in the back of the B1sat (shown is pic B) is the same size as the feedhorn tube on the FSS (pic C). You cut one hole (pic A) in the backplate of the B1sat (also pic A). Cut down the FSS feed to just enter the hole in the B1sat .
so you have FSS, backplate, FSS feed all bolted together. Put that on the B1sat . It bolts right on.
In pic F it shows the FSS feed just entering the Hole in the B1sat.

Results are a compromise. i wanted to get Cozi and the music channels, but all i could get was the music channels .
i did not notice any C-band differences. this was for bird 103.
the bud for this is the 7.5 perfect 10.
Sometime, i will just put up another dish to get cozi tv.
anyway, finished product is a stacked combo.

 

[FaT Air]

Looks like 'it was meant to be'. Getting the music, but not COZI, do you have the polarity 20 to 26° offset from the C band? CW when looking at the back of the LNBF.

 

[kodaz]

i did try that, but it didnt work.
The FSS alone in the c-band scalar does pull in cozi. I just hurts the signal too much to run thru the B1sat

 

[Pixl]

Interesting test, nice machining. I wonder if you could try extending the Ku throat with a section of pipe (same inside dia ) to the front of the C band feed.

 

[Titanium]

Good suggestion, Pixl!

I had worked with a manufacturer a few year back with a very similar concept. Extending the proper diameter waveguide to the KU section improved the KU-band performance with minimal effect on the C-band performance. Never completed the project and stopped before developing the feedhorn to adjust the KU reflector illumination.

Maybe this is a project to resume again now that we have 3D printers readily available...

 

[kodaz]

i will look at putting a longer feed on it and see what happens. it will be easy enough to make.
i was hoping for some good ideas to make this better.


would you happen to know if the tube must be aluminum, or can i use steel?

edit- made a feed out of stainless and it worked amazingly well. cozi is in like flint at 70 q
Feed goes to the end of the c-band lnb
i did lose 3840 on the c-band side, but i have the other ions and the pbs channels which is all i watched on that bird.On most c-band tps, i lost 10 q easy.

 

[Titanium]

Any metal will carry the RF. Just be sure to match the inner diameter.

 

[KE4EST]

Yep as long as it is metal.

 

[Pixl]

made a feed out of stainless and it worked amazingly well. cozi is in like flint at 70 q
Feed goes to the end of the c-band lnb
i did lose 3840 on the c-band side, but i have the other ions and the pbs channels which is all i watched on that bird.On most c-band tps, i lost 10 q easy.

So Ku went up, C went down. If not too much might be the better compromise to get all in one. Nice test.

 

[Titanium]

If you want to do some more experimenting to maximize performance, adjust the length of the KU waveguide.

 

[FaT Air]

Maybe a slight readjustment of the Focal Length to get C band back 'up'? (just thinking as I really don't know)

 

[kodaz]

Funny thing is that i had to pull the b1Sat way back on the scalar to get c-band as good as it is.
This weekend i may play around with feed lengths.
not much going to happen during the week with working 10 hr days.
it is just a little bud.7.5' . If i learn anything good, i will post it.
edited in a pic to show the modified stainless feed in post 6.
i do have everything i want on that bird now in BANDSTACKED!!

 

[Titanium]

Funny thing is that i had to pull the b1Sat way back on the scalar to get c-band as good as it is.

It makes sense if you consider that by moving the LNBF away from the reflector, you are moving the convergence point further in front of the blocking KU waveguide. This is why I am suggesting to experiment with the length of the KU waveguide. Determine the balance between blocking the C-band signal convergence point and entering in the C-band cavity and capturing enough of the KU signal in the KU waveguide.

 

[Hockeynut]

Nice work Kodaz.I did something very similar when I took a Chaparral Bullseye and made a Ku feed tube with a c120 flange on it.I spent countless hrs on adjustment of the Ku waveguide.This was done on a 10' KTI!..I never could get satisfactory results on Cband with this setup..Losing many of the high FEC S2 signals I eventually just went back to a Cband Ortho.Do believe with the Cband loss a project like this is well suited for a very large dish..12' minimum.

Not trying to deter at all with my comment kodaz...I am a tinkerer also..

Here is a pic of what I made.

 

[polgyver]

Yep as long as it is metal.

Not necessarily, according to some inventors ...
There is a U.S. patent from year 1988, its number : 4,785,306
The inventor used teflon rod, dia 5/16, as a waveguide, he got this dia dividing metal waveguide dia (0.625" or 16 mm) by teflon dielectric constant, = 2.1
He stated that such a small rod did not impede C-band waves. He located the Ku LNB also behind C-band LNB.
Anybody has heard about this patent's implementation?
Cheers, polgyver

 

[FaT Air]

Interesting - http://www.google.com/patents/US4785306
Has anyone seen one of these 'in the wild'?

 

[kodaz]

i am game, someone point me in the direction of a dielectric 5/16" rod .

is Delrin rod an option?

They list teflon, so perhaps i will give that a go

 

[Pixl]

It would seem to me best guess that the degradation of the C performance might be corrected by increasing the size of the c band circular wave guide, maybe to match the distance from wall to wall adding the size of the Ku waveguide.

 

[kodaz]

could be. I did make the ku waveguide 1/8 to1/4 inch longer than the c-band. pulled back like it is would maybe do what you are saying.
the id of the ku is 5/8" . This is a change from the 3/4 ss -the first test were run on. (new is galv conduit)

This made a huge improvement. 3840 is back at 70 Q. Cozi is rock solid at 70 q also
The c-band signal is good enough that it will have to be replaced with another lnb , scanned and compared with the modded one to see how it fares. a modded scalar may be needed here.
The current mod is a keeper. i have other b1sats to mess with.

Amazon had 5/16 teflon rod. going to give that a go also later .

i only have about 30 minutes an evening this week before dark, so will do better tests this weekend.

 

[pendragon]

What you're doing is pretty similar to the implementation of commercial dual ortho feeds. I've done a lot of testing of these on all the C-band dishes I've ever owned, and I've found the introduction of the Ku waveguide causes about a 0.5 dB loss in CNR on C-band. On Ku-band you tend to get a fairly erratic beam pattern. Unless the f/D of the dish is large, say >= 0.4, you will under-illuminate it on Ku, but because of the size of C-band dishes that may not be meaningful. On the other hand many C-band dishes have mediocre surface tolerances from a Ku perspective, that will cause losses, and the length of the Ku waveguide also contributes. The best I've been able to accomplish on Ku-band with this type of feed is about 2 dB worse than theoretical. Still the combination is attractive on my 2.6 m solid Birdview.