NEC-LIST: Helix design question

As you may already know, the resonant frequency (highest gain) occurs when the circumference=2*pi*radius is ~1 wavelength:
c/(2*pi*R)=0.29978/(2*pi*0.01638)~=2.9 GHz

Your pitch is atan2(0.4156,(19*pi*2*0.01638))*180/pi=12°
That's an appropriate pitch for an axial mode helix but not necessarily optimal.

Since you are feeding it on the edge, your resonant frequency will be about 140 ohms.
Since your feed is pretty long, your resonant impedance may be higher, maybe 200 ohms.

If you want it lower in frequency, scale both the radius and the length in the GH command, and the feed height in the GW command, by
~2.9/f where f is your desired frequency in GHz for max gain.

Larry Goldstein
Harris Corporation
321-727-5561

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