Peter Körner designed this Yagi array with 19 elements on a 5.08-meter (200″) boom. It uses five reflectors, a horizontal folded dipole, and a halfwave coaxial balun. Unlike other high-performance designs, the 19.3 has no phasing lines that can induce current in the boom and degrade the pattern.
I modeled the 19.3 with the AO 8.50 Antenna Optimizer program. This image shows the antenna geometry.
This overhead view shows the horizontal folded dipole and nearby elements. The driven element is long, the two dipole currents are unequal, and their relative magnitude and phase change with frequency. This varies the critical coupling to the closely spaced first director across the FM band, a neat trick without moving parts. In this particular design, the feedpoint must be at the forward conductor.
Below are calculated performance figures for a segmentation density of 21 segments per halfwave. Mismatch loss is due to SWR. Wire loss is due to conductor resistance. Mismatched gain is forward gain including wire and mismatch losses. F/R is the ratio of forward power to that of the worst backlobe in the rear half-plane. The SWR reference impedance is 300Ω.
88.000 MHz: Impedance 330 + j16 ohms
SWR 1.11
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 8.72 dBd
F/R 31.55 dB
93.000 MHz: Impedance 331 - j31 ohms
SWR 1.15
Mismatch Loss 0.02 dB
Wire Loss 0.01 dB
Mismatched Gain 9.59 dBd
F/R 38.15 dB
98.000 MHz: Impedance 301 - j14 ohms
SWR 1.05
Mismatch Loss 0.00 dB
Wire Loss 0.02 dB
Mismatched Gain 10.46 dBd
F/R 36.08 dB
103.000 MHz: Impedance 301 + j30 ohms
SWR 1.10
Mismatch Loss 0.01 dB
Wire Loss 0.04 dB
Mismatched Gain 10.65 dBd
F/R 33.49 dB
108.000 MHz: Impedance 285 - j14 ohms
SWR 1.07
Mismatch Loss 0.01 dB
Wire Loss 0.19 dB
Mismatched Gain 9.51 dBd
F/R 30.96 dB
Korner 19.3 Yagi Free Space Symmetric 98.000 MHz 22 6061-T6 wires, meters r0 = 1.03 ; reflector lengths r1 = .99 r2 = .96 x0 = 0 ; reflector positions x1 = 0 x2 = .04 z1 = .335 ; reflector heights z2 = .73 de = .825 ; driven element length de1 = .48 ; driven element positions de2 = .55 d1 = .659 ; director lengths d2 = .672 d3 = .657 d4 = .64 d5 = .633 d6 = .617 d7 = .611 d8 = .629 d9 = .602 d10 = .606 d11 = .616 d12 = .619 d13 = .574 p1 = .64 ; director positions p2 = .752 p3 = .945 p4 = 1.11 p5 = 1.374 p6 = 1.612 p7 = 1.844 p8 = 2.272 p9 = 2.788 p10 = 3.256 p11 = 3.83 p12 = 4.377 p13 = 5.08 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 p10 -d10 0 p10 d10 0 .01 1 p11 -d11 0 p11 d11 0 .01 1 p12 -d12 0 p12 d12 0 .01 1 p13 -d13 0 p13 d13 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.
88–108 MHz