HALF TURN QUADRIFILAR HELIX AERIAL USING 10mm COPPER TUBE BASIC DESIGN CRITERIA Frequency 137.5 MHz Aspect ratio of Height to Diameter 1.45 Mean Perimeter to Wavelength ratio 1.07 Deviation of Perim. to Wl. ratios +/- 3.27 % Small loop Perimeter to Wavelength ratio 1.035011 Small loop Diameter to Wavelength ratio .1649298 Small loop Height to Wavelength ratio .2391482 Large loop Perimeter to Wavelength ratio 1.104989 Large loop Diameter to Wavelength ratio .1760808 Large loop Height to Wavelength ratio .2553172 DIMENSIONS INCHES MILLIMETRES Wavelength 85.83909 2180.313 SMALL LOOP Dimensions to tube centres Diameter 14.15742 359.5985 Height 20.52826 521.4178 Length of helix 30.26478 768.7253 Perimeter 88.8444 2256.648 Dimensions of tubes less 4 mm per joint for 90 deg. end feed elbows Diameter tube length less 8 mm 13.84246 351.5985 Half diameter tube less length 8 mm 6.76375 171.7992 Helix tube length less 8 mm 29.94982 760.7253 Formed radius for helix tube 13.39292 340.1801 Formed end lift for helix tube (each end) 3.157105 80.19046 LARGE LOOP Dimensions to tube centres Diameter 15.11462 383.9112 Height 21.91619 556.6713 Length of helix 32.31101 820.6996 Perimeter 94.85125 2409.222 Dimensions of tubes less 4 mm per joint for 90 deg. end feed elbows Diameter tube length less 8mm 14.79965 375.9112 Half diameter tube length less 8 mm 7.242347 183.9556 Helix tube length less 8 mm 31.99605 812.6996 Formed radius for helix tube 14.29843 363.18 Formed end lift for helix tube (each end) 3.370559 85.61221