Quadix
The Quadix is a circularly polarized helical antenna with parasitic elements. This version for FM broadcast reception has eight elements on a 200" boom. It is arranged for right-circular polarization.
I optimized the design with the AO 8.01 Antenna Optimizer program with its response flattener. This image shows the antenna geometry and analysis segmention. Blue dots indicate segment boundaries. The red dot indicates the feedpoint.
Modeling Results
Below are calculated performance figures for a segmentation density of 20 segments per turn. Mismatch loss is due to SWR. Wire loss is due to conductor resistance. Mismatched gain is forward gain, including wire and mismatch losses. The gain reference is a linear dipole in a free-space circular field. F/B is the ratio of forward power to that directly to the rear. The SWR reference impedance is 300 ohms. Ellipticity is the ratio of minimum to maximum response, expressed in dB, as an incident linearly polarized signal rotates through all polarizations.
88.000 MHz: Impedance 295 + j44 ohms
SWR 1.16
Mismatch Loss 0.02 dB
Wire Loss 0.01 dB
Mismatched Gain 11.21 dBd
Ellipticity -5.25 dB
F/B 27.01 dB
90.000 MHz: Impedance 329 + j22 ohms
SWR 1.12
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 11.72 dBd
Ellipticity -3.31 dB
F/B 40.10 dB
92.000 MHz: Impedance 332 + j5 ohms
SWR 1.11
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 11.98 dBd
Ellipticity -2.01 dB
F/B 48.53 dB
94.000 MHz: Impedance 326 - j1 ohms
SWR 1.09
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 12.17 dBd
Ellipticity -1.24 dB
F/B 39.25 dB
96.000 MHz: Impedance 318 + j0 ohms
SWR 1.06
Mismatch Loss 0.00 dB
Wire Loss 0.01 dB
Mismatched Gain 12.36 dBd
Ellipticity -1.15 dB
F/B 32.68 dB
98.000 MHz: Impedance 311 + j6 ohms
SWR 1.04
Mismatch Loss 0.00 dB
Wire Loss 0.01 dB
Mismatched Gain 12.59 dBd
Ellipticity -1.61 dB
F/B 28.99 dB
100.000 MHz: Impedance 304 + j14 ohms
SWR 1.05
Mismatch Loss 0.00 dB
Wire Loss 0.01 dB
Mismatched Gain 12.87 dBd
Ellipticity -2.28 dB
F/B 26.50 dB
102.000 MHz: Impedance 297 + j26 ohms
SWR 1.09
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 13.12 dBd
Ellipticity -3.15 dB
F/B 24.10 dB
104.000 MHz: Impedance 299 + j35 ohms
SWR 1.12
Mismatch Loss 0.01 dB
Wire Loss 0.02 dB
Mismatched Gain 13.28 dBd
Ellipticity -3.76 dB
F/B 22.67 dB
106.000 MHz: Impedance 281 + j23 ohms
SWR 1.11
Mismatch Loss 0.01 dB
Wire Loss 0.03 dB
Mismatched Gain 13.46 dBd
Ellipticity -2.80 dB
F/B 25.10 dB
108.000 MHz: Impedance 266 + j14 ohms
SWR 1.14
Mismatch Loss 0.02 dB
Wire Loss 0.08 dB
Mismatched Gain 11.75 dBd
Ellipticity -1.59 dB
F/B 23.32 dB
Circular Patterns
Linear Patterns
Antenna File
Quadix Circularly Polarized Array Free Space 98 MHz 180 copper wires, inches x = 3.637175 ; DE pitch x1 = x/10 x2 = 2*x1 x3 = 3*x1 x4 = 4*x1 x5 = 5*x1 x6 = 6*x1 x7 = 7*x1 x8 = 8*x1 x9 = 9*x1 x10 = 10*x1 x11 = 11*x1 x12 = 12*x1 x13 = 13*x1 x14 = 14*x1 x15 = 15*x1 x16 = 16*x1 x17 = 17*x1 x18 = 18*x1 x19 = 19*x1 x20 = 20*x1 x21 = 21*x1 x22 = 22*x1 x23 = 23*x1 x24 = 24*x1 x25 = 25*x1 x26 = 26*x1 x27 = 27*x1 x28 = 28*x1 x29 = 29*x1 x30 = 30*x1 x31 = 31*x1 x32 = 32*x1 x33 = 33*x1 x34 = 34*x1 x35 = 35*x1 x36 = 36*x1 x37 = 37*x1 x38 = 38*x1 x39 = 39*x1 x40 = 40*x1 r = 22.18902 ; REF length h = 22.12968 ; DE length t = 17.09717 ; DIR1 length s = 17.4614 ; DIR2 length u = 16.64809 ; DIR3 length w = 17.23402 ; DIR4 length y = 17.30923 ; DIR5 length z = 16.2991 ; DIR6 length r1 = .3090*r r2 = .5878*r r3 = .8090*r r4 = .9511*r r5 = r q1 = .3090*h q2 = .5878*h q3 = .8090*h q4 = .9511*h q5 = h s1 = .3090*s s2 = .5878*s s3 = .8090*s s4 = .9511*s s5 = s t1 = .3090*t t2 = .5878*t t3 = .8090*t t4 = .9511*t t5 = t u1 = .3090*u u2 = .5878*u u3 = .8090*u u4 = .9511*u u5 = u w1 = .3090*w w2 = .5878*w w3 = .8090*w w4 = .9511*w w5 = w y1 = .3090*y y2 = .5878*y y3 = .8090*y y4 = .9511*y y5 = y z1 = .3090*z z2 = .5878*z z3 = .8090*z z4 = .9511*z z5 = z l = 200 ; boom length ref = 16.0108 ; REF position de = 3.196437 ; DE position dir1 = 20.24313 ; DIR1 position dir2 = 46.88218 ; DIR2 position dir3 = 87.3642 ; DIR3 position dir4 = 121.646 ; DIR3 position dir5 = 155.4413 ; DIR3 position dir6 = l - ref ; DIR4 position d = .375 ; element diameter shift x de rotate x -26 1 0 q5 0 x1 q4 q1 d 1 x1 q4 q1 x2 q3 q2 d 1 x2 q3 q2 x3 q2 q3 d 1 x3 q2 q3 x4 q1 q4 d 1 x4 q1 q4 x5 0 q5 d 1 x5 0 q5 x6 -q1 q4 d 1 x6 -q1 q4 x7 -q2 q3 d 1 x7 -q2 q3 x8 -q3 q2 d 1 x8 -q3 q2 x9 -q4 q1 d 1 x9 -q4 q1 x10 -q5 0 d 1 x10 -q5 0 x11 -q4 -q1 d 1 x11 -q4 -q1 x12 -q3 -q2 d 1 x12 -q3 -q2 x13 -q2 -q3 d 1 x13 -q2 -q3 x14 -q1 -q4 d 1 x14 -q1 -q4 x15 0 -q5 d 1 x15 0 -q5 x16 q1 -q4 d 1 x16 q1 -q4 x17 q2 -q3 d 1 x17 q2 -q3 x18 q3 -q2 d 1 x18 q3 -q2 x19 q4 -q1 d 1 x19 q4 -q1 x20 q5 0 d 1 x20 q5 0 x21 q4 q1 d 1 x21 q4 q1 x22 q3 q2 d 1 x22 q3 q2 x23 q2 q3 d 1 x23 q2 q3 x24 q1 q4 d 1 x24 q1 q4 x25 0 q5 d 1 x25 0 q5 x26 -q1 q4 d 1 x26 -q1 q4 x27 -q2 q3 d 1 x27 -q2 q3 x28 -q3 q2 d 1 x28 -q3 q2 x29 -q4 q1 d 1 x29 -q4 q1 x30 -q5 0 d 1 x30 -q5 0 x31 -q4 -q1 d 1 x31 -q4 -q1 x32 -q3 -q2 d 1 x32 -q3 -q2 x33 -q2 -q3 d 1 x33 -q2 -q3 x34 -q1 -q4 d 1 x34 -q1 -q4 x35 0 -q5 d 1 x35 0 -q5 x36 q1 -q4 d 1 x36 q1 -q4 x37 q2 -q3 d 1 x37 q2 -q3 x38 q3 -q2 d 1 x38 q3 -q2 x39 q4 -q1 d 1 x39 q4 -q1 x40 q5 0 d rotate end shift end 1 dir1 t5 0 dir1 t4 t1 d 1 dir1 t4 t1 dir1 t3 t2 d 1 dir1 t3 t2 dir1 t2 t3 d 1 dir1 t2 t3 dir1 t1 t4 d 1 dir1 t1 t4 dir1 0 t5 d 1 dir1 0 t5 dir1 -t1 t4 d 1 dir1 -t1 t4 dir1 -t2 t3 d 1 dir1 -t2 t3 dir1 -t3 t2 d 1 dir1 -t3 t2 dir1 -t4 t1 d 1 dir1 -t4 t1 dir1 -t5 0 d 1 dir1 -t5 0 dir1 -t4 -t1 d 1 dir1 -t4 -t1 dir1 -t3 -t2 d 1 dir1 -t3 -t2 dir1 -t2 -t3 d 1 dir1 -t2 -t3 dir1 -t1 -t4 d 1 dir1 -t1 -t4 dir1 0 -t5 d 1 dir1 0 -t5 dir1 t1 -t4 d 1 dir1 t1 -t4 dir1 t2 -t3 d 1 dir1 t2 -t3 dir1 t3 -t2 d 1 dir1 t3 -t2 dir1 t4 -t1 d 1 dir1 t4 -t1 dir1 t5 0 d 1 dir2 s5 0 dir2 s4 s1 d 1 dir2 s4 s1 dir2 s3 s2 d 1 dir2 s3 s2 dir2 s2 s3 d 1 dir2 s2 s3 dir2 s1 s4 d 1 dir2 s1 s4 dir2 0 s5 d 1 dir2 0 s5 dir2 -s1 s4 d 1 dir2 -s1 s4 dir2 -s2 s3 d 1 dir2 -s2 s3 dir2 -s3 s2 d 1 dir2 -s3 s2 dir2 -s4 s1 d 1 dir2 -s4 s1 dir2 -s5 0 d 1 dir2 -s5 0 dir2 -s4 -s1 d 1 dir2 -s4 -s1 dir2 -s3 -s2 d 1 dir2 -s3 -s2 dir2 -s2 -s3 d 1 dir2 -s2 -s3 dir2 -s1 -s4 d 1 dir2 -s1 -s4 dir2 0 -s5 d 1 dir2 0 -s5 dir2 s1 -s4 d 1 dir2 s1 -s4 dir2 s2 -s3 d 1 dir2 s2 -s3 dir2 s3 -s2 d 1 dir2 s3 -s2 dir2 s4 -s1 d 1 dir2 s4 -s1 dir2 s5 0 d 1 dir3 u5 0 dir3 u4 u1 d 1 dir3 u4 u1 dir3 u3 u2 d 1 dir3 u3 u2 dir3 u2 u3 d 1 dir3 u2 u3 dir3 u1 u4 d 1 dir3 u1 u4 dir3 0 u5 d 1 dir3 0 u5 dir3 -u1 u4 d 1 dir3 -u1 u4 dir3 -u2 u3 d 1 dir3 -u2 u3 dir3 -u3 u2 d 1 dir3 -u3 u2 dir3 -u4 u1 d 1 dir3 -u4 u1 dir3 -u5 0 d 1 dir3 -u5 0 dir3 -u4 -u1 d 1 dir3 -u4 -u1 dir3 -u3 -u2 d 1 dir3 -u3 -u2 dir3 -u2 -u3 d 1 dir3 -u2 -u3 dir3 -u1 -u4 d 1 dir3 -u1 -u4 dir3 0 -u5 d 1 dir3 0 -u5 dir3 u1 -u4 d 1 dir3 u1 -u4 dir3 u2 -u3 d 1 dir3 u2 -u3 dir3 u3 -u2 d 1 dir3 u3 -u2 dir3 u4 -u1 d 1 dir3 u4 -u1 dir3 u5 0 d 1 dir4 w5 0 dir4 w4 w1 d 1 dir4 w4 w1 dir4 w3 w2 d 1 dir4 w3 w2 dir4 w2 w3 d 1 dir4 w2 w3 dir4 w1 w4 d 1 dir4 w1 w4 dir4 0 w5 d 1 dir4 0 w5 dir4 -w1 w4 d 1 dir4 -w1 w4 dir4 -w2 w3 d 1 dir4 -w2 w3 dir4 -w3 w2 d 1 dir4 -w3 w2 dir4 -w4 w1 d 1 dir4 -w4 w1 dir4 -w5 0 d 1 dir4 -w5 0 dir4 -w4 -w1 d 1 dir4 -w4 -w1 dir4 -w3 -w2 d 1 dir4 -w3 -w2 dir4 -w2 -w3 d 1 dir4 -w2 -w3 dir4 -w1 -w4 d 1 dir4 -w1 -w4 dir4 0 -w5 d 1 dir4 0 -w5 dir4 w1 -w4 d 1 dir4 w1 -w4 dir4 w2 -w3 d 1 dir4 w2 -w3 dir4 w3 -w2 d 1 dir4 w3 -w2 dir4 w4 -w1 d 1 dir4 w4 -w1 dir4 w5 0 d 1 dir5 y5 0 dir5 y4 y1 d 1 dir5 y4 y1 dir5 y3 y2 d 1 dir5 y3 y2 dir5 y2 y3 d 1 dir5 y2 y3 dir5 y1 y4 d 1 dir5 y1 y4 dir5 0 y5 d 1 dir5 0 y5 dir5 -y1 y4 d 1 dir5 -y1 y4 dir5 -y2 y3 d 1 dir5 -y2 y3 dir5 -y3 y2 d 1 dir5 -y3 y2 dir5 -y4 y1 d 1 dir5 -y4 y1 dir5 -y5 0 d 1 dir5 -y5 0 dir5 -y4 -y1 d 1 dir5 -y4 -y1 dir5 -y3 -y2 d 1 dir5 -y3 -y2 dir5 -y2 -y3 d 1 dir5 -y2 -y3 dir5 -y1 -y4 d 1 dir5 -y1 -y4 dir5 0 -y5 d 1 dir5 0 -y5 dir5 y1 -y4 d 1 dir5 y1 -y4 dir5 y2 -y3 d 1 dir5 y2 -y3 dir5 y3 -y2 d 1 dir5 y3 -y2 dir5 y4 -y1 d 1 dir5 y4 -y1 dir5 y5 0 d 1 dir6 z5 0 dir6 z4 z1 d 1 dir6 z4 z1 dir6 z3 z2 d 1 dir6 z3 z2 dir6 z2 z3 d 1 dir6 z2 z3 dir6 z1 z4 d 1 dir6 z1 z4 dir6 0 z5 d 1 dir6 0 z5 dir6 -z1 z4 d 1 dir6 -z1 z4 dir6 -z2 z3 d 1 dir6 -z2 z3 dir6 -z3 z2 d 1 dir6 -z3 z2 dir6 -z4 z1 d 1 dir6 -z4 z1 dir6 -z5 0 d 1 dir6 -z5 0 dir6 -z4 -z1 d 1 dir6 -z4 -z1 dir6 -z3 -z2 d 1 dir6 -z3 -z2 dir6 -z2 -z3 d 1 dir6 -z2 -z3 dir6 -z1 -z4 d 1 dir6 -z1 -z4 dir6 0 -z5 d 1 dir6 0 -z5 dir6 z1 -z4 d 1 dir6 z1 -z4 dir6 z2 -z3 d 1 dir6 z2 -z3 dir6 z3 -z2 d 1 dir6 z3 -z2 dir6 z4 -z1 d 1 dir6 z4 -z1 dir6 z5 0 d shift x -ref 1 0 r5 0 0 r4 r1 d 1 0 r4 r1 0 r3 r2 d 1 0 r3 r2 0 r2 r3 d 1 0 r2 r3 0 r1 r4 d 1 0 r1 r4 0 0 r5 d 1 0 0 r5 0 -r1 r4 d 1 0 -r1 r4 0 -r2 r3 d 1 0 -r2 r3 0 -r3 r2 d 1 0 -r3 r2 0 -r4 r1 d 1 0 -r4 r1 0 -r5 0 d 1 0 -r5 0 0 -r4 -r1 d 1 0 -r4 -r1 0 -r3 -r2 d 1 0 -r3 -r2 0 -r2 -r3 d 1 0 -r2 -r3 0 -r1 -r4 d 1 0 -r1 -r4 0 0 -r5 d 1 0 0 -r5 0 r1 -r4 d 1 0 r1 -r4 0 r2 -r3 d 1 0 r2 -r3 0 r3 -r2 d 1 0 r3 -r2 0 r4 -r1 d 1 0 r4 -r1 0 r5 0 d 1 source Wire 6, end1 Freqs: 88 89 90 92 94 96 99 102 105 108 Tradeoffs: Gain 25%, F/B 75% F/B region: 90-180 deg Freq Wtg: Worst
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Updated July 8, 2007
