Peter Körner in Lund, Sweden, designed this Yagi array. It has 15 elements on a 3.73-meter (147″) boom, five reflectors, a horizontal folded dipole, and uses a halfwave coaxial balun.
Unlike log-Yagis, the 15.12 has no phasing lines that can induce current in the boom and degrade the pattern.
This overhead view shows the horizontal folded dipole. It is unusually long and the two conductor currents differ, as does their coupling to the first director. Because of these factors, conductor spacing strongly affects antenna performance and can be optimized. It provides only a weak degree of freedom for a vertical folded dipole.
This shows how the 15mm × 5mm folded dipole conductors join at the ends. The element mount on the right is a repurposed support for 10mm hydraulic fluid lines.
I modeled the antenna with the AO 9.50 Antenna Optimizer program using a segmentation density of 28 segments per halfwave. Forward gain includes mismatch and conductor losses. F/R is the ratio of forward power to that of the worst backlobe in the rear half-plane.
Frequency Impedance SWR Mismatch Conductor Forward F/R
MHz ohms Loss dB Loss dB Gain dBd dB
88 344 + j32 1.18 0.03 0.01 7.82 32.24
89 355 + j18 1.19 0.03 0.01 7.94 34.01
90 362 + j3 1.21 0.04 0.01 8.08 34.47
91 363 - j10 1.21 0.04 0.01 8.22 34.44
92 361 - j22 1.22 0.04 0.01 8.36 34.46
93 355 - j31 1.21 0.04 0.01 8.52 34.53
94 345 - j37 1.20 0.04 0.01 8.67 34.33
95 337 - j39 1.18 0.03 0.01 8.83 34.26
96 327 - j40 1.17 0.03 0.01 8.99 34.33
97 318 - j39 1.15 0.02 0.01 9.14 34.64
98 308 - j36 1.13 0.02 0.01 9.29 34.42
99 296 - j31 1.11 0.01 0.02 9.42 34.27
100 284 - j22 1.10 0.01 0.02 9.52 34.10
101 271 - j8 1.11 0.01 0.02 9.59 34.08
102 263 + j15 1.15 0.02 0.03 9.61 34.18
103 268 + j39 1.19 0.03 0.03 9.56 34.45
104 289 + j56 1.21 0.04 0.04 9.43 34.54
105 321 + j43 1.17 0.03 0.05 9.21 33.97
106 315 - j6 1.05 0.00 0.06 8.86 33.23
107 260 - j31 1.20 0.04 0.09 8.36 32.11
108 191 - j41 1.62 0.25 0.13 7.66 30.38
Körner 15.12 Free Space Symmetric 98 MHz 18 6061-T6 wires, meters r0 = 1.015 ; reflector halflengths r1 = 1.006 r2 = .985 x0 = 0 ; reflector positions x1 = 0 x2 = .11 z1 = .326 ; reflector heights z2 = .73 de = .805 ; driven element halflength de1 = .431 ; driven element positions de2 = .546 d1 = .657 ; director halflengths d2 = .659 d3 = .65 d4 = .617 d5 = .615 d6 = .608 d7 = .635 d8 = .624 d9 = .565 p1 = .654 ; director positions p2 = .827 p3 = 1.086 p4 = 1.41 p5 = 1.629 p6 = 1.888 p7 = 2.376 p8 = 2.98 p9 = 3.73 1 x2 -r2 -z2 x2 r2 -z2 .01 ; reflectors 1 x1 -r1 -z1 x1 r1 -z1 .01 1 x0 -r0 0 x0 r0 0 .01 1 x1 -r1 z1 x1 r1 z1 .01 1 x2 -r2 z2 x2 r2 z2 .01 1 de1 -de 0 de1 de 0 .01148 ; driven element 1 de2 -de 0 de2 de 0 .01148 1 de1 -de 0 de2 -de 0 .015 1 de1 de 0 de2 de 0 .015 1 p1 -d1 0 p1 d1 0 .01 ; directors 1 p2 -d2 0 p2 d2 0 .01 1 p3 -d3 0 p3 d3 0 .01 1 p4 -d4 0 p4 d4 0 .01 1 p5 -d5 0 p5 d5 0 .01 1 p6 -d6 0 p6 d6 0 .01 1 p7 -d7 0 p7 d7 0 .01 1 p8 -d8 0 p8 d8 0 .01 1 p9 -d9 0 p9 d9 0 .01 1 source Wire 7, center
The 11.48mm diameters are cylindrical equivalents of the 15mm × 5mm rectangular folded dipole conductors. The 15mm conductors are short tubes that connect the folded dipole ends. Peter says to measure the driven element length to the element ends, not to the centerline of the short tubes.
The following table shows the degradation of average performance over 88, 93, 98, 103, and 108 MHz in dB when changing a single dimension by ±3 mm (±1.5 mm for symbols that represent element half-length).
Symbol Gain F/R
r0 0.00 0.02
r1 0.00 0.01
r2 0.00 0.01
x0 0.00 0.00
x1 0.00 0.00
x2 0.00 0.02
z1 0.00 0.00
z2 0.00 0.03
de 0.00 0.03
de1 0.00 0.05
de2 0.01 0.08
d1 0.01 0.03
d2 0.00 0.04
d3 0.00 0.07
d4 0.00 0.09
d5 0.01 0.05
d6 0.00 0.05
d7 0.04 0.19
d8 0.01 0.04
d9 0.00 0.06
p1 0.02 0.05
p2 0.01 0.09
p3 0.01 0.09
p4 0.00 0.01
p5 0.00 0.03
p6 0.00 0.04
p7 0.01 0.08
p8 0.00 0.09
p9 0.00 0.03
This is Georgiy Markiev's 15.12 in Petrozavodsk, Russia. It rotates here.
88–108 MHz