[amsat-bb] L-Band Antenna

["Joel B. Black" <jbblack@xxxxxxxxxxxxxx>]

I thought it would be interesting, with all the talk of S-Band, to do the
calculations for an L-band helix for AO-40.  I did this in an Excel
spreadsheet so some of the formatting may look wrong.  Also, I couldn't get
Excel to calculate tangent, cosine, and square root correctly so those were
done manually.  Some of you "gurus"  can confirm or discount my
calculations.  I got them from the _The_Radio_Amateur's_Satellite_Handbook_
1st. edition, page 10-11:

Free space wavelength (inches) = 11,800/f (MHz) 9.30inches (23.62 cm)
Diameter  = C/p 2.96inches (7.52 cm)
Spacing between turns  = C(tan a) 2.06inches (5.23 cm)
Distance between reflector
     and start of first turn  = S/2 1.03inches (2.62 cm)
Reflector side (minimum)  0.6l 5.58inches (14.17 cm)
Wire length per turn  = C/cos a 9.53inches (24.21 cm)
Total wire length  = nL + 1/2  144.75inches (367.67 cm)

Circumference: C =  1.00
Pitch angle: a =  12.5°
Turns: n =  15
Antenna center frequency: 1269.250

73,
Joel, K2SAT

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