nabih said:
Hello everybody
This is an S.O.S
Is there anybody who had successfully grafted a black ultra inverto lnb onto a prime focus feed
Thanks for the answer
I think you'll find that this specific question has been answered in post #7. One such thing is Pipino's conversion:
http://www.satellites.co.uk/forums/...verto-twin-black-ultra-flange-convertion.html
But please note this is a destructive process, and may not give the results you are looking for. Probably better off ordering a C120 Inverto off the internet.
Also note that the Black Ultra will most likely work as-is with your dish, you just won't get full signal strength.
The reason is that the F/D factor, which expresses the focal depth and beam width generally is higher on an offset dish (about 0.60-0.65) than a PF one (0.30-0.45).
Which F/D ratio the LNB is made for is determined by the feedhorn design.
The feedhorn inside the Black Ultra generally supports an F/D of about 0.60 (if I remember correctly).
This means that if you point a Black Ultra at a PF dish with an F/D of, say, 0.38, it will only see a smaller part of the reflector surface (probably something like 1/2 to 2/3 of the dish face). In other words it will probably work, but you will not use all of the surface of your reflector.
This can be a serious source of disappointment if you can't see Astra 1N after having obtained a 1.8m dish for the purpose.
This is why you are better off with an LNB with the correct feedhorn than slapping the Black Ultra on it.