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)	Bandwidth (@ -3dB)	Beam width (@ -3dB)
Fmax/Fmin: Fmax: MHz Fmin: MHz	Fmax/Fmin: Fmax: MHz Fmin: MHz	degrees