The results

Legend. The letters in the image are used in the table below.

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Results
Wavelength	Ideal diameter (internal)	Gain
mm	D=mm	dBi
Conductor diameter	Winding step (between centers)	Separation of the adapter section
d=mm	S=mm	a=mm
Total conductor length	Minimum reflector diameter	Total antenna length
mm	R=mm	L=mm
Bandwidth (@ -1dB) Fmax/Fmin	Bandwidth (@ -3dB) Fmax/Fmin