Which LNB to go for

[richardsth]

I've just changed my 1.5 prime focus dish for a 1.8 prodelin and I have a query with the oreintation of the LNB. When I fitted my c120 invacom to the feedhorn, it had to sit at a 45 degree to get good results. With the 1.8 feedhorn, this only has four holes and when it's connected up to the lnb, it now sits at 90 degrees. Because of the way the feedhorn holes drilled, I only have the choice of fitting it up or down, is this right ? Is this the correct lnb for this dish or am I missing something here ? If anyone else has a Prodelin 1.8 , what LNB are you using and how does it sit ?

Cheers Rik.

 

[embalse]

I am not sure I understand your question 100%, but if you have a c120 invacom and a 1.8 prodelin, you should be using the correct CM feedhorn (Model: 611606007). This comes with 8 holes, but only 4 bolts are needed as only 4 holes can be aligned correctly.

 

[rolfw]

Does the feedhorn not rotate in its holder? perhaps you could upload a photo to show us?

 

[richardsth]

sorry, perhaps I wasn't clear enough. The feed horn has a peak (like a baseball cap) over the front and a 50-0-50 scale on it, so I assume that this faces upwards. Having four mounting holes on it, they only line up with inverto lnb at 90 degress. Which means that the lnb is at right angles to the dish. I can rotate the whole lot around as I wish but wouldn't this defeat the object of having the scale and peak at the top.? So if anyone has a 1.8 offset dish and inverto lnb, what position does the lnb sit at?

 

[embalse]

So if anyone has a 1.8 offset dish and inverto lnb,?

Are you using a c120 invacom (as in your 1st post), or a inverto lnb as in your 4th post?

.

 

[rolfw]

The LNB should normally mount vertically can you not change the holes you use?

The scale on the horn is for skew, as I mentioned earlier, a couple of pictures would help.

 

[Huevos]

C120 only bolts on one way round (unless you only use two screws) but I went to a job the other day and trying to be quick I left the feedhorn on the dish and tried to bolt on the new quad Inverto the guy supplied to replace his Invacom twin. Anyway, to cut a long story short I discovered that the Inverto C120 is not machined with the same skew as the Invacom by quite some amount (maybe 90º different).

 

[richardsth]

I think that there is something peculiar with the inverto LNB holes. Only two ever do line up with the feed horn and to fit all four, then it's 90 degrees out. I'm going to bin this anyway as I reckon its shagged and go for an Invacom. Hopefully that will fit with the feed horn the right way up and the LNB in the correct oreintation.

Rik

 

[richardsth]

In reply to embalse's mail, it's an inverto LNB that doesn't fit correctly.

 

[Robbo]

There's an adapter here, maybe of some use

_http://www.smw.se/res/pdf/omtfeedhornadapters1.pdf

 

[Huevos]

The LNB I fitted was a "White Tech". Was yours the same?

 

[Channel Hopper]

With the 1.8 feedhorn, this only has four holes and when it's connected up to the lnb, it now sits at 90 degrees. Because of the way the feedhorn holes drilled, I only have the choice of fitting it up or down, is this right ? Is this the correct lnb for this dish or am I missing something here ? If anyone else has a Prodelin 1.8 , what LNB are you using and how does it sit ?

The Prodelin feedhorn (23/24mm clamp ?) is designed to work with a limited number of LNBs, and the C120 type flange on modern LNBs isn't one of them. The design gets worse when the polarmount system is fitted as the skew settings will be way out for a number of satellites on the arc.

The dish/feed manual will most likely state WC75 fitting, which is a different kettle of fish, and you would have to get it machined with a flange to fit it to anything that is now supplied in Europe.
Prodelin and the two UK distributors do not believe there is any requirement to adapt the parts (or supply an adapter) to fit the most common LNBs around.

 

[richardsth]

I knew I wasn't going bonkers ! I tried fitting both the Inverto and Invacom but they have to be 90 degress out to fit the four screws. But if I just use two screws it's on and facing the right way, so now I've got all my channels coming in clear. Funnily enough, the recommended LNB that they provide is one of the big jobbies like my old echostar quad band unit and that can go on in any orientation.