Advice Needed Inverto black ultra feedhorn .. F/d ??

antrabe said:
which lnb is advised to use in ku band for prime focus
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@antrabe


Normally, the feed arrangement for Ku band on a prime focus dish has a C120 flange fitting so a C120 LNB is required. Popular makes of C120 LNB for Ku band are Inverto and Invacom. Personally, I have a preference for the Invacom C120 LNB's as they have given slightly higher signal levels compared to Inverto in tests I have done.

The price of quad output C120 LNB's has gone up a lot recently. Unless you need 4 outputs, a good LNB for a prime focus dish would be an Invacom dual output C120 LNB or an Invacom single output C120 LNB.
 
@RimaNTSS
I wonder how Inverto reply " IBU suitable with antennas have F/d = 0.6 " then added " opening angle is 84' " ?
and we know that when F/d = 0.6 the angle should be 90'
F/d = 0.65 the angle should be 84'
can anybody let me know why is that difference ?? how come that ?
 
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mirrors said:
I wonder how Inverto reply " IBU suitable with antennas have F/d = 0.6 " then added " opening angle is 84' " ?
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They actually added aperture angle not opening angle, that could have different meaning.
I think it is mess with all those terms, at least for me. First of all F/D of the offset dish.....it does not make sense. Another case is "F/D equivalent"
In the case of LNB the opening angle is not the same as illumination angle. Graphically it can look something like that GDST08001789_detail-1 (Custom).webp
 
@RimaNTSS
yes I should say ( illuminate or aperture angle ) which I meant is the recieving angle of LNBF ..
but my wonder is about .. as waht I know ( maybe I'm right or not ) the best recieving will be when both angles ( opening of antenna dish ) and ( aperture of LNBF ) match ? isn't it like that ??
so how 84' of LNBF match dish with 0.6 F/d ??
 
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For example, opening angle of Channel Master antenna is 80* (almost sharp), and illumination angle of IBU is 84*. So, IBU will little bit over-illuminate the dish and that is not so bad. Almost perfect match.
And, BTW, F/D-equivalent of Channel Master is 0.68.
 
@RimaNTSS
yes that's right . one of my friends cut the upper ring of the feedhorn of IBU for his PFA with 0.45 F/d .
He told me things went good but I can't recomened such a thing .
and about offset dish and ( equivelqnt ) F/d I think it is so easy to understand .
 
mirrors said:
so how 84' of LNBF match dish with 0.6 F/d ??
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AFAIK the f/D=0.6 and illumination angle = 70 degrees are just a kind of "standard" values for manufacturers of offsetdishes, opposed to the PFdishes where no standard exists, to enable them to make/use "standard" LNBf's for offset dishes.

So the f/D=0.6 for a (IBU) LNB I think is just referring to the standards, as an LNB for an offset dish, with no factual base for that specific LNB.
I hope the value of 84 degrees for the IBU is right, though?....

Just my assumption, mind!

Greetz,
A33
 
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