Does Inverto 'narrow feed' compromise performance?

AlanX

Active Member
I know that 'narrow feed' is for several LNBs on a bar, but, if it doesn't compromise reception performance, why aren't ALL LNBs made this way, whether on a bar or not? Or is it simply more expensive to manufacture, so you'd only choose 'narrow feed' if you really needed it?
 

MartinPickering

Well-known Member
This type of LNB used to be called a "bullet" or "dildo" design. Instead of a horn, it uses a special plastic dielectric "bullet" to focus the reflected signal, from the dish, onto the internal antennas in the LNB. The dielectric is generally more expensive, although I suspect we are talking pennies. However, in a competitive market, pennies can count.

I was under the impression that such LNBs tended to be less "wideband" in their frequency-handling capabilities but modern manufacturing and design techniques have probably minimised this problem.
 

Geofbob

Novice Member
I know that 'narrow feed' is for several LNBs on a bar, but, if it doesn't compromise reception performance, why aren't ALL LNBs made this way, whether on a bar or not? Or is it simply more expensive to manufacture, so you'd only choose 'narrow feed' if you really needed it?
It's tempting to think that once an "improvement" in functionality and/or design is developed in a product - it should then become universal (subject of course to patent & contract issues).

But in practice improvements in one aspect are often coupled with down-sides in others - as Martin Pickering says might be the case with Narrow Feed LNBs. And sometimes even the supposed improvements are arguable at best, & illusory at worst.

After all, in an ideal world, we'd all be using the same sort of flush toilet - but we aren't!
 

AlanX

Active Member
Thanks for your responses. I have just called Inverto themselves. They say that the "slim feed" (as they term it) is specially fabricated with higher quality components than the standard LNB "to achieve the same results"; hence it is more expensive. They also said that, if you don't need 2.5 degree separation on a bar, then you are better off with the standard LNB. My conclusion is that they've had to push things to achieve slim feed performance, but it still may not be as good as a standard LNB (and probably more expensive!). As I'm going for 28/19/13 I think I'll go for standard LNBs on a Triax bar. Hope this is useful to anyone else on the horns of this particular dilemma.
 

xavk1

Novice Member
I have personally mixed and matched my LNBs on a Triax arm attached to Triax 110D, using Alps bullet LNBs where necessary and standard for the rest.

I have 5E (standard), 9E (narrow), 13E (narrow), 16E (standard, dual) and 19E (narrow). All works great in London :thumbsup:
 

MartinPickering

Well-known Member
Anyone needing fairly close-spacing might try the Sharp BS1R9EL100A (single-output) LNB which is just 42mm diameter at the widest point (the cap).
 

Chris Muriel

Distinguished Member
Dielectric horns do require more expensive materials to work well and unless "military grade" material is used (at higher cost) they'll never be as efficient as a traditional horn as used on normal consumer LNBFs.
The dielectric constant of the insulator has to be extremely high to avoid losses (I recall reading about this years ago in what was then a standard University work, Radio and Electronic Engineering by Frederick Emmons Terman).
 

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