Procedure for Making a Parabolic Dish

Careful........ a lot of privacy laws make a parabolic dish illegal

Hello Techno.

Thank you very much for your comments, but I need the Parabolic Dish for see free TV don´t worry.

Any way thanks

I know nothi.....ing

Assuming you are transmitting from your house to your garage.....

A parabolic dish is too sensitive to direction. 1/2 degree off and you will receive nothi...ing

If the dish is visible, police alarms will ring.

A regular dish is still directional and is less sensitive to exact direction and will do the same job. It will also blend in with the legal dishes.

One still needs a Television Broadcast Receiving Licence to view it, so it isn't 'free' as such.

Hello Techno,

I have a few assumptions as to why privacy laws would make a parabolic dish illegal, but would you mind elaborating on your comment?

Ah ha! That's what I had assumed...

http://www.binarywolf.com/249/parabolic.htm

Depends what U want it for...If you google solar cooker you will find stuff on parabolic solar reflectors. The are sites with the formulae etc...depends what you want to make it out of....cut a load of wooden profiles...just like do it, see how it turns out...then do it again but better....works for me.

You can find the calculations on these 2 pages:

http://www.analyzemath.com/parabola/parabola_work.html

http://www.analyzemath.com/parabola/parabola_focus.html

What seems to be the problem - the shape or the manufacturing?

The shape has been sorted out above.

If it is manufacturing - please advise - material and equipment available.

The equation of a parabolic dish is y = SQRT [h² - (h²/a²) x²]

where h = 1/2 minor axis (or dish depth) & a = 1/2 major axis (or ID)

You can select any parabolic with different measurements for both major and minor axes, try a parabolic with its major axis = 2 times its minor axis (called 2: 1 ellipsoidal, and dish depth h = 1/4 ID)

If we considered that a = h = R, it means that the shape is a circle with radius R and the equation shall be :

y = SQRT [R² - (R²/R²) x²] = SQRT [R² - X²]

y² = R² - X²

X² + y² = R² (equation of circle)

Unless you are making a big one, I just go to the flea market and buy a used one. Several yaers ago most of the satelite TV people changed them form round to oval so they accept 2 LMB's and there should be a lot of old ones out there.

you can buy one cheap off ebay.........then you just need bootleg software to interpret the signals.......

but then as soon as you get up and running, they'll change the signal mix and you just keep going in circles :)

check out a ARRL site, the have a very good book on this http://www.arrl.org/