Parabolic Antennas

[ebjco]

Hi Guys,

 

I am looking for help or directions to a tutorial that can show me how to draw a Parabolic for a Microwave Antanna using AutoCad 2004.

 

Thanks

 

Ernie

[David Bethel]

Here's an interesting discussion of curves in AutoCAD

 

http://discussion.autodesk.com/thread.jspa?messageID=1206419

 

It can be quite a daunting task. -David

[Squirreldip]

Roadway vertical curves are parabolic... Here's (basically) how Land Desktop draws vertical curves:

 

First, draw a polyline with two line segments, say from -1,1 to 0,0 to 1,1.

 

Second, set SPLINETYPE to 5 (Quadratic B-spline)

 

Third, set SPLINESEGS to 65 (or higher if you need more segments)

 

Last, PEDIT the polyline and Spline...

 

(Of course you'll need to play with the actual coordinates of the polyline)

 

Not really knowing where you want to go from here...

 

Change your UCS - orthoGraphic to Front then enter PLAN. Array the parabola polar and change your UCS back to world...

[fuccaro]

For more control I would use the exact formula. Here is how:

;draw a parabolic solid
; Miklos Fuccaro [email="mfuccaro@hotmail.com"]mfuccaro@hotmail.com[/email]
; Nov. 2005
;
(defun c:parabola( / p dx x rep osmode)
 (setq p (getdist "\nY+SQRT(2*p*x)\t P=")
   dx 0.1        ;increment in X direction
   rep 50        ;repetitions
   x (- dx)
   )
 (if p (progn
     (setq osmode (getvar "OSMODE"))
     (setvar "OSMODE" 0)
     (command "PLINE")
     (repeat rep
       (command (list (setq x (+ x dx)) (sqrt (* 2 p x))))
       )
     (command (list (* (1- rep) dx) 0) "c")
     (command "revolve" "l" "" "x" "")
     (setvar "OSMODE" osmode)           
     )
   (princ "nothing to do!")
   )
 (princ)
 )

 

[anjali]

i didnot understand the formula

can u plz specify what exactly p specify

if we want to draw a parabola of width 14 focus 3.5 then what is the value of p? in the above mentioned formula.

[fuccaro]

While I was in school I learnt that the equation of the parabola is Y=SQRT(2PX)

SQRT means square root. This is the equation I used to draw the solid in the image above. I would say, it looks like a parabola

Let me find a book and I will get back.

Oh, and welcome in the forum!