Dual C Dual Ku LNBF??

[budfoot]

IIRC way back when, there was a combination dual C dual Ku prime focus lnbf available. Is anyone still making something like that? The related question, of course, is...does anyone have a bullseye feedhorn lying around that they want to part with. I have lots of lnb's, but I really hate to pop $400 for a new Chaparral Bullseye.

Unfortunately, it's a real PITA to run more than one receiver on either a C/Ku lnbf or a corotor. I'm just about ready to ditch my analog receiver and run the positioner with a GBox. The problem is dealing with band and polarity selection. None of the FTA receivers will run a corotor servo for polarity, so an lnbf or a bullseye is a better way to go. A 4 or 5 in multiswitch will easily handle the situation on a bullseye or a dual C dual Ku lnbf, but the readily available single C single Ku lnbfs just won't work in that situation.

Any helpful suggestions more than welcome. I guess the other question concerns the availability of a 14/18 to servo interface box. Easy enough to build, I guess. Any commercially available?

Thanks

Budfoot

 

[pendragon]

One can find ADL (sometimes branded as Astrotel) dual ortho feeds for about half the price of a Bullseye and I doubt there's anything significantly different in performance. If your BUD isn't too deep or too shallow, this is probably the best off-the-shelf solution for getting both C and Ku on the same dish. But it is a compromise and a single ortho feed for C will outperform it. Like any dual band feed, the Ku section is even more compromised and there is the issue that most BUDs are not the best solution for Ku anyway. But you are likely aware of these limitations and a dual ortho is a VERY good solution.

With that said, I have been mulling over the challenge of doing better than a dual ortho on a BUD. I'm sitting on the fence, but I'm considering a solid or very well made petal ~2.4m for maximum CNR on Ku. However I would also like to have C-band for backup purposes. I've scratched down some calculations, and based on my success with combining two C-band single orthos (linear and circular) in a siamese feed configuration, I believe a siamese C/Ku feed will likely out-perform a dual ortho by a small margin on C and a big margin on Ku. There are some technical challenges and I don't want to anyone to assume this is the only way to go, but it is an alternative.

 

[budfoot]

I saw the pix of your siamese setup and I wonder if something like that with a dual C lnbf in one hole and a dual Ku lnbf in the other or a dual C/Ku lnbf in each hole. I wonder if it would be possible to co-mount a small throat Ku lnbf without a scalar ring and manage to get the focus and tracking accurate enough to work. Interesting bit of doing that. ADL makes a C-band ortho with a dbs lnbf mounted in it and Chaparral used to make something similar.

I looked at the ADL bullseyes, and although they're less money than the Chaparrals, they're still $200 or so.

Continuing cogito cogito. Figure something out eventually.


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Budfoot

 

[Scott Greczkowski]

I would love one of these, I have been looking at WSI's new dual output LNB and would love to see a combined feed with C/KU.

 

[pendragon]

budfoot - I did some quick tests and a proper Ku-band scalar was just as important as a C-band scalar when either was used on a BUD. I haven't done the math, but I suspect combo C/Ku feeds suffer because of this and related field and pattern control issues. My concept is to cut a hole in a C-band scalar ring to accommodate a prime-focus Ku-band feed I have lying around.

Scott - I'm motivated to make this work, but no one seems able to sell me a heavy-duty 2.4m petal dish with a polar mount, and nothing adequate is coming up around here in the salvage department.

 

[crackt]

I would love one of these, I have been looking at WSI's new dual output LNB and would love to see a combined feed with C/KU.

the dual output cband lnbfs ive tested are no where near as good as the combo c/ku lnbfs ive tested. im no where near as thorough as pendragon, if he wants ill send him gear to test for me with his methods. i do like his methods. but i am a "tester" and what id like to think of as a rigorous real world tester. when i do spring for an SA i will test all my gear fairly (with mentoring and guidance from someone alot smarter than me like pendragon). i do suffer of canadianitis and have to pay premiums for all the gear i buy, but i do try and own all of the new stuff. most of it sits on top of my fridge with the best residing in my working dishes. i really think though that without developing a proper feed servo controller for our digital stbs that the lnb versus lnbf debate will never have a fair comparison. so many projects, so little time. haha.

crackt out,.

 

[John Popper]

budfoot - I did some quick tests and a proper Ku-band scalar was just as important as a C-band scalar when either was used on a BUD. I haven't done the math, but I suspect combo C/Ku feeds suffer because of this and related field and pattern control issues. My concept is to cut a hole in a C-band scalar ring to accommodate a prime-focus Ku-band feed I have lying around.

Scott - I'm motivated to make this work, but no one seems able to sell me a heavy-duty 2.4m petal dish with a polar mount, and nothing adequate is coming up around here in the salvage department.

im doing some testing for something similar, will share the results by the end of the week

 

[Anole]

food for thought:

While you do seem to be going in a different direction, let me answer the original questions.

- dual output C-band only LNBFs are available from SatelliteAV (GeoSatPro C2), Sadoun (GeoSatPro C2), and Galaxy (DMX242).
They're quite inexpensive, and easy to experiment with.

- there are still some Pansat receiver models which will drive a corotor servo.
I believe the 2700 ? and the 3500sd will do that.
Both are standard def only, and while not obsolete, are certainly not what most of us want for the future.

- the 12/18 volt servo interface box was described quite well on this forum some time ago.
Building one wouldn't be too difficult.
However, it would not output both H & V polarity at the same time, should that be required, and would continue to rely on older servo technology.

- a suitable Ku feedhorn might be a challenge.
I would probably think first of the AF-120 from Invacom, and marry it to any of their flange-mount, dual output LNBf's.
The QPF-031 comes to mind, if somewhat expensive.

If there is a way to convert a less expensive two-output Ku LNBF to the AF-120, I haven't thought of it.
Oh, wait, the old Primestar LNBs with H & V output might work.
Well, that's an area for some thought.


Bandstacked Approach:

This is not for everyone, but I do bring it up just to offer it for consideration.

The Ku LNB could be a bandstacked Eagle Aspen or DishNetwork FSS device.
It mounts directly to the AF-120 feedhorn above.

The C-band LNBF could be an Eagle Aspen B1 Sat stacked device.
It comes with a suitable scalar ring.

Previously discussed on the forum, a DishNetwork DP-34 multiple-output diseqc switch suports three LNBs and outputs to four receivers.

 

[SatelliteAV]

In our exhaustive testing for the development of the GEOSATpro line of C-Band LNBFs we have observed that the dedicated C-Band LNBF consistently outperformed the C/KU models. While C/KU LNBFs fill a need for the current limits of receivers, no LNBF ( C or CK) has matched the performance of a quality feedhorn, high quality LNBs and adjustable skew.

I believe that until a mechanism is developed to fine tune LNBF skew, LNBFs will not match the performance demands for motorized systems.

 

[budfoot]

<snip>
My concept is to cut a hole in a C-band scalar ring to accommodate a prime-focus Ku-band feed I have lying around.

That approach sounds like what the ADL people did with their C/Ku/DSS feedhorn. A good dual C lnbf in a good scalar ring combined with a dual Ku prime focus would totally do the trick. Presumably the C band could reasonably suffer a small bit of off-center misalignment to accommodate getting the Ku nuts on.

I'm already off to build a 14/18 to servo converter just to tide me over. That and a GBox will at least get me out of my analog receiver slave mode and let the Azbox run the show.


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Budfoot