Elliptical Dishes

[kstuart]

Hello,

What is the theory behind elliptical dishes (with single LNBFs) ?

Is there any advantage over a circular dish of equivalent area ?

 

[Anole]

simplistic answer

Taller would get you signal gain.
Wider would get you finer accuracy for close birds.
Just -bigger- would get you both.
So, if you need the resolution but not the gain... the elliptical dishes work out.


edit: reworded for clarity...

Bigger dishes get you more gain and more accuracy of pointing.
Just-taller dishes just get you more signal (gain).
Just-wider dishes just get you more aiming accuracy and side-satellite rejection.
.. So, if you need the resolution but not the gain... the elliptical dishes are a good solution.

 

[kstuart]

Taller would get you signal gain.
Wider would get you finer accuracy for close birds.

Globecast switched to an elliptical dish, but they are only on IA5, with no strong DBS sats nearby. (And their receivers are rumored to be "weak" and so a bigger dish is recommended for them, i.e. taller)

Primestar was the most famous users of elliptical dishes with single LNBFs. I don't know where their satellites were located...

 

[Mr Tony]

Primestar was at 85 & ended at 89

I used an oblong DirecPC dish (39x23) to get a feed on G3 that had horrible interference from IA5. The 30" couldn't get a solid signal and the DPC dish got it with a really good signal (this was a couple years ago)

 

[kstuart]

So it seems Globecast are not using it for any engineering reason (which is probably why Sadoun ships their receivers with a round dish). Probably they got a good deal from Channel Master, because CM could use the same production line that they tooled up for the defunct Primestar...