Which dish

[amdman]

All,
Would you suggest a 90cm offset dish or an 36 elliptical dish for FTA?

[rainman]

I like the fortec 90cm it seems to be just the right size for FTA.

[wejones]

Aren't all offset dishes elliptical? Since that's the case, I'm not sure what the difference is between a 36" elliptical and a 90CM elliptical?

My guess is that what is being referred to here is an elliptical that is wider than tall, rather than taller than wide? I think that a dish that is taller than wide is made that way basically to look like a circle to the lnbf, so that the lnbf doesn't over or under illuminate the dish.

On the other hand, I think the dishes that are wider than tall are made that way so that it can be viewed with multiple lnbfs, each of which illuminates the dish properly vertically, but under illuminates horizontally. So the effective size of such a dish would pretty much be defined by the height of the dish as seen from the perspective of the lnbf, while the effective size of a taller than wider dish is pretty much the width of the dish, which is also the height as seen from the perspective of the lnbf. Not sure if that came across clearly.

However, I've always been curious about something, and that is, if a dish were wider than high, but the lnbf was designed to illuminate the full width, I am wondering whether this would improve resolution to that consistent with a circular dish of the size of the width, although with gain consistent with the average of height/width. I'm sure I didn't explain that question clearly, so what I'm asking is whether the width of a dish is more important than the height, relative to resolving two nearby satellites, since the width is along the arc? The equations I've seen seem to suggest that resolution is only dependent on gain, which would mean that it didn't matter whether the long elliptical axis was along the arc or perpendicular to the arc??? (Hope that was clear.) Intuitively, it seems like you might be able to get better resolution with a short wide dish than with a tall thin dish, although this would mean extra noise due to over illumination.

[amdman]

Thanks for your expert advise. I have a 90cm taller than wider dish and did not know if a 36inch wide might provide better reception.

[wejones]

Originally Posted by amdman

Thanks for your expert advise. I have a 90cm taller than wider dish and did not know if a 36inch wide might provide better reception.

My 90CM is something like 33.5" wide by 37" high. If the 36" wide is shorter than 37" high, I think you could probably compare the two based on their heights. If the 36" wide is taller than wide, then I'd think it would be a bit better. However I really doubt that there is much difference between the two, unless the 36" dish is wider than tall, and significantly shorter than 37". If the differences are not great, the quality of construction is probably more important than the size.