which is better for better Quality signal

[manuelpaz]

Hi guys .


well i like to see which will get better quality signal a regular sadoun 6 footer dish or a 6 footer offset dish ( channel master ) i know that i got to do a madification for the lnb but my reason is that i can get these dishes easy i some car dealers done just buy the regulars 6 footer from Sadoun, and if i get a 6 footer offset dish the LNB where it will be install same as the ku band lnb or in the middle like the regular c band dish.


I really thank u 4 ur cmmments.

 

[Anole]

In another thread, Linuxman is currently mounting a C-band LNBF to one of those six foot offset Prodelin dishes.
Here's a link well into the thread, past all the Ku work he did.
Scroll down 'till you see the C-band LNBF, and read his comments.
It may give you some encouragement for using that dish.
For best performance, I think it deserves a conical scalar, though.

And Iceberg, our moderator, has many posts 'n threads on use of his six foot Fortec Star dishes.
Being prime focus, the standard scalars which come with C-band LNBFs are the correct hardware.

The Fortec is available with a motorizable mount.
The Prodelin would require some serious work!

 

[truckracer]

theoretically an offset dish design is more efficient. as for the real world. I don't think you will see much difference

 

[jamestheman]

I got a 4 foot offset dish a while back and am trying to figure out how to properly install my new bsc 621 lnb on it,

 

[Larry1]

With both dish's being 6', the gain should be close to the same for both. The more important factor may be the F/D ratio, as it will determine the adjacent satellite rejection.

 

[manuelpaz]

hello Larry1

thank 4 ur comments really make me happy and i'll do that. this is great having some guys helping to reach the skies and no doing some little dishes just like dishnetwork or directv.

hey thank u again.

 

[B.J.]

With both dish's being 6', the gain should be close to the same for both. The more important factor may be the F/D ratio, as it will determine the adjacent satellite rejection.

I'm curious relative to what you base this statement on?

I think I know where you're coming from, ie from an optical standpoint you intuitively expect to get more resolution as you go to higher F/D ratios, and longer focal lengths give you more magnification to resolve close together objects, etc. However every equation I've seen for resolution or beam width of a satellite dish generally say that resolution is completely dependent upon gain, and that gain is pretty much completely dependent on dish size, etc. If there are equations out there that involve F/D ratio, I'd appreciate a link.

From experience, ignoring any equations, I really had much better results in this respect, with a relatively high F/D Sami dish, than I currently have with a LOW F/D Orbitron dish. (I really miss my Sami, but it stayed with my old house.)
However I also think that the high F/D Sami also had more gain, despite being the same size as the Orbitron, mainly because the feed had a better view of the outside edges of the dish, which are pretty much wasted space on the Orbitron.

But anyway, are you aware of any web page with theoretical discussion with equations, that involve F/D with respect to resolution/beam width? Just curious.

EDIT: another aspect of this, is that offset dishes generally have very HIGH F/D ratios. However the dish is a small section of the complete parabaloid, and if the F/D ratio were calculated based on th entire parabaloid, the F/D ratio would be much smaller. Ie this is somewhat similar to stopping down the iris on a camera, or using one of those lunar covers to a telescope to get a clearer image when you don't need the light gathering from the entire mirror.