KU LNB on a prime focus dish? (1 Viewer)

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alicante

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Jun 3, 2004
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I don't think my reply to this old thread adhered to the thread. So here I go again:

I know is an old thread but after doing searches, this is the closest I could find. I have an old prime focus Cband dish and I would like to install a feed horn and lnb to it to receive Ku circular signal. Can anyone please help.
 

Mr Tony

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Nov 17, 2003
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broke off post off ancient thread. Its easier to start a new thread

What are you trying to receive? There isnt really any free KU Circular out there
 

SatPhreak

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Apr 19, 2007
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ICE is right there is very limited KU circular, but I have done it on a 10' dish with an offset circular LNBF beside the Cband LNB. Even though the KU LNBF is not matched to the dish, it may pick up circular birds, since circular birds are so high powered. It also depends if your dish is KU capable, IE small mesh, less than 1/4" holes in the mesh or solid. The other option is to get a KU LNB with a prime focus KU feed (hard to find) or a C/KU feedhorn with C and KU LNB's.
 

enb141

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Aug 5, 2009
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For circular Ku on Prime Focus dishes you are out of luck, there's no LNB Prime Focus for circular KU (at least not easy to find). If you insist using an adapter for a Offset LNB then you will lose a lot of its potential due to F/D that is different from Prime Focus and Offset dishes.
 

SatelliteAV

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If you want to receive circular DBS/DSS (12.2 - 12.75Ghz) check out the Invacom prime focus feed horn and the QPF-031 LNB.
 

FaT Air

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Feb 27, 2010
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I'd put a standard C band lnbf on it. Think that would give you much more to watch. Especially if your receiver is S2 and HD capable.
 

Anole

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Sep 22, 2005
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to reinforce some of the above...

How big a BUD, and where are you located?

If you are outside the footprint of the circular Ku birds, your BUD may not do any good, for many of the reasons listed above.

If you are inside the footprint of the circular birds, there are a lot of options:
- surplus Ku dishes with circular LNBFs can be found in the trash, use one of those
- one member hung a 30" Ku dish on the lower rim of his BUD; you could do that with a 20" trash dish as above
- the prime focus Invacom AF-120 (?) feed and any circular LNB that would bolt to it is an excellent idea, but probably overkill if you are inside the footprint
- bolt a regular circular KU LNBF to the side of your existing scalar, and offset the dish about 4..5..6 degrees to get the Ku signal; (mount Ku LNBF to the east side of your scalar, and drive the dish a few degrees east of normal to get the circular signal)
- the dual band LNBFs won't do circular Ku under any circumstances.

I strongly recommend a small stand-alone surplus (junk) Ku dish.

But, let's ask why you want circular.
If it's for a subscription, the fixed dish is much better; those receivers go crazy if they drop signal once set up.
 

alicante

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Jun 3, 2004
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Gentlemen:
First, I want to apologize for taking a long time to answer this thread, but I was down in Colombia, south america where I have a small farm out in the country and have no internet there because being so far up the hill with very few houses. Well, I just got back again. What I did was I bought a used 12' solid aluminum used dish down there, and took with me a BSC621-2 to use with it. I wanted to take my dish subscription with me but when I got there and opened the suit cases found that my wife have taken out the receiver so she could put more of her darn shoes in it. So I could not do my experiment. So I am still lost on this project.

To recap the whole thing, I have a legal subscription, but down in Colombia the signal is very weak and is almost impossible to find and buy an big enough offset dish. There for, I decided to try it with a BUD and the BSC621-2. I will be going again this summer and would not want to take my dish receiver with me if is not going to work with the mentioned hardware.

Thank you very much for all the time all of you have taken to help me out on this.
 

SatelliteAV

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The BSC621-2 does not receive KU circular. It received KU and C-band linear polarity.

If you insert the dielectric slab it will receive KU-band linear and C-band circular. If you wish to receive the circular polarity DBS KU frequencies (12.2 - 12.75), you will need a LNBF that receives that range of frequencies and is also circular polarized.
 

alicante

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Jun 3, 2004
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Gosh, that does changes my game plan. Now from what you say, I need to search for another toy. Now my problem is of how this gadget may be called as a search name.
Thanks a lot to direct me into the right direction.
 

alicante

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Jun 3, 2004
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Now, have been doing lots of reading tonight and I do have an Invacom QPH-031 Quad Polar Circular Linear Ku Band LNBf LNB. Correct me if I am wrong, but would this LNBF capture the whole surface of a BUD using a Ku Adapter bracket for a Prime Focus Dish
 

SatelliteAV

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Now, have been doing lots of reading tonight and I do have an Invacom QPH-031 Quad Polar Circular Linear Ku Band LNBf LNB. Correct me if I am wrong, but would this LNBF capture the whole surface of a BUD using a Ku Adapter bracket for a Prime Focus Dish

The Invacom QPH-031 is designed for an offset dish and a radically different focal distance and ratio. It will severely under-illuminate a larger dish and not capture reflected signals from the entire reflector surface.

Going back to post #5 of this thread. [url]http://www.satelliteguys.us/free-air-fta-discussion/267271-ku-lnb-prime-focus-dish.html#post2645905[/URL] To properly illuminate or capture the entire surface of the dish consider the Invacom QPF-031 and matching feedhorn.
 

alicante

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Jun 3, 2004
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satelliteAV,
I thank you for trying to help me out on this, but I have searched for the QPF-031 but only the QPH-031 shows everywhere.
 

alicante

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Jun 3, 2004
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Wait, finally found it with its matching feedhorn. Thanks a lot. SatelliteAV
 

alicante

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Jun 3, 2004
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Yes dishman dan, that is exactly where I found them. Also the matching feed is on eBay. Just that I see the prices for the lnbf is so high. Actually I don't need a quad. Just single circular would be plenty.
 

alicante

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Jun 3, 2004
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I see there is a QDF-031 LNBF also. What is the difference between this one and the QPF-031?
 

SatelliteAV

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alicante said:
I see there is a QDF-031 LNBF also. What is the difference between this one and the QPF-031?

Google is our friend.....

The "H" version is a LNBF = with integrated feedhorn. Designed for offset dishes with higher f/d. Not suitable for prime focus dishes.

The "F" version is a LNB = no integrated Feedhorn and requires mounting to a feedhorn. Can be used on both offset and prime focus design dishes with appropriate feedhorn.

QDF-031: KU-band Universal linear LNB with 4 outputs.
QPF-031: KU-band Standard linear LNB on two outputs and DBS circular LNB on two outputs.

If you want optimum reception of circular polarity KU-band DBS signals on a prime focus dish, use the QPF-031 with the matching feedhorn and connect to the circular polarity output(s).
 
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alicante

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Jun 3, 2004
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Thanks Satellite AV, you really know your stuff for sure. I appreciate your help. Then for this QPF-031 LNBF I should match it with the Invacom ADF-120 Feed Horn?
 
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