Alas, satsig is not accurate; I tested that.
Also Parabola Calculator 2.0 for
offset dishes (using Paul Wade's method) is not accurate, as it pre-assumes bottom at vertex. A slight difference there causes abberations for the focal point. (For PF dishes I believe this calculator is OK, though!)
Parabola6 is highly accurate for focal point calculations of paraboloid dishes, though. And gives a nice drawing of the results.
However I find the depth measurement of that calculator rather difficult; I find the measuring procedure that I wrote above simpler, and by using the top/bottom spots again
I think you get more accuracy in the input measures.
So I made a calculator that can use three different types of input values:
- center point input values, such as mine and Parabola6's;
- deepest point input values, such as Parabola Calculator 2.0 (but without the incorrectness of the unnecessary preassumption of bottom at vertex). I have noticed it is very hard to find the exact deepest point, though;
- LNBfeedhorn point input values, when you know the feedhorn position is accurate (simple method, to find the effective focal distance of offset dishes, for e.g. multifeedcalculations).
If a dish is wider than high, but it is still paraboloid in form (to reduce impact from neighbouring satellites), with the water method you can still find the "effective width", and do the calculations.
If a dish is wider than high, and it is a multifeed dish, it is usually parabolic in the vertical sense, and circular in the horizontal sense. That is also the case with toroidal dishes.
I have a calculation method for those dishes in my mind, needing also the water method. And it would not be a proper 'calculation', but a step by step algoritm (by repeated steps, algoritm in the original sense, I believe?), to come very very near the true value.
But that calculation is still on my 'to do' list, for somewhere in the future, and the method is still untested...
Example of calculation of my triax-115 with the 'dish-center' method is added.
Also the other calculation methods, and needed inputs, are shown.
View attachment 137571
greetz,
A33