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RE: JavaScript Axial-Mode Helix Calculator



Gain is in dBi, but apparently is measured, not theoretical-- or it at least 
isn't as optimistic as the original Kraus gain eq. (I'll add the  "i" in dBi 
next time I do a revision)

The pitch is 12.8 degrees... maximum gain pitch...supposedly...

>From the ARRL UHF/Microwave Experimenters article by KA1GT:

"..The diameter of the conductor used for the helix has very little effect 
on helix characteristics when the helix is operating in the axial mode..."  
For reasonable diameters, it doesn't matter.

I'd have to guess that the "spacing between turns" is from one end of the 
conductor to the other.  Maybe someone can correct me on this.. I do know 
(after making 5 or 6 helices) that the bandwidth of the antenna is so great, 
for reasonable diameters again, it will make
little or no difference if I am wrong about this!!  Helices are very 
forgiving dimensionally due to the wide operating bandwidths.

I also corrected a problem (actually a bug with MSIE) that would not let 
gain be calculated in Internet Exploder.  It's fixed now, but make sure 
there are no spaces in the number of turns field, or it won't work.  (It 
used to work with leading/trailing spaces in Netscape.. but...it doesn't 
now... oh well...it's not rocket science, or is it?)

Fred W0FMS




>From: KB7WW Art Moe <kb7ww@chatusa.com>
>To: "Frederick M. Spinner" <fspinner@hotmail.com>
>Subject: RE: JavaScript Axial-Mode Helix Calculator
>Date: Sun, 10 Dec 2000 16:34:11 -0800
>
>Fred,
>
>Program looks and works great. Just a couple of questions.
>
>1. Does the wire size inter into the Math.  like #16 vs 3/8 tube?
>
>2. Are the Circumference and Diameter at the center line of the wire?
>
>3. Is the gain in DBi or DBd I would guess DBi
>
>
>If any of this matters you might want to add it to your Calculator
>page.
>
>
>Art
>KB7WW

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