Körner 15.10
This is an outdoor receiving antenna for the FM broadcast band designed by Peter Körner. It is a Yagi array with fifteen elements (five reflectors) on a 3.73-meter (147") boom. It uses a folded-dipole driven element with 300-ohm feedpoint. To feed with 75-ohm coax, Peter uses a halfwave coaxial balun with negligible loss.
This photo shows the earlier 15.9 version. Notice the conventional vertical folded dipole.
This shows the 15.10 antenna geometry. Some of the element lengths have changed, but the main difference is that the folded dipole is now in the horizontal plane.
This overhead view shows the folded dipole and nearby elements. The two dipole conductor currents are unequal and their relative magnitudes and phases vary with frequency, shifting the effective source position in the horizontal plane. This varies the critical coupling to the closely spaced first director with frequency. When mounted this way, the folded dipole conductor spacing provides an additional degree of freedom that can be used to fine-tune antenna performance. This is a very neat trick, essentially providing something for nothing. In this particular design the feedpoint must be at the forward conductor.
Modeling Results
Below are calculated performance figures for a segmentation density of 50 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/B is the ratio of forward power to that directly to the rear. The SWR reference impedance is 300 ohms.
88.000 MHz: Impedance 302 + j25 ohms
SWR 1.09
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 7.83 dBd
F/B 30.23 dB
90.000 MHz: Impedance 320 + j22 ohms
SWR 1.10
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 8.11 dBd
F/B 33.06 dB
92.000 MHz: Impedance 328 + j18 ohms
SWR 1.11
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 8.41 dBd
F/B 36.19 dB
94.000 MHz: Impedance 331 + j18 ohms
SWR 1.12
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 8.72 dBd
F/B 40.85 dB
96.000 MHz: Impedance 332 + j17 ohms
SWR 1.12
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 9.04 dBd
F/B 41.25 dB
98.000 MHz: Impedance 328 + j13 ohms
SWR 1.11
Mismatch Loss 0.01 dB
Wire Loss 0.02 dB
Mismatched Gain 9.34 dBd
F/B 35.68 dB
100.000 MHz: Impedance 304 + j16 ohms
SWR 1.06
Mismatch Loss 0.00 dB
Wire Loss 0.02 dB
Mismatched Gain 9.56 dBd
F/B 32.43 dB
102.000 MHz: Impedance 274 + j57 ohms
SWR 1.25
Mismatch Loss 0.05 dB
Wire Loss 0.03 dB
Mismatched Gain 9.58 dBd
F/B 32.57 dB
104.000 MHz: Impedance 314 + j133 ohms
SWR 1.54
Mismatch Loss 0.20 dB
Wire Loss 0.04 dB
Mismatched Gain 9.22 dBd
F/B 40.00 dB
106.000 MHz: Impedance 363 + j22 ohms
SWR 1.22
Mismatch Loss 0.04 dB
Wire Loss 0.07 dB
Mismatched Gain 8.74 dBd
F/B 31.39 dB
108.000 MHz: Impedance 238 + j78 ohms
SWR 1.45
Mismatch Loss 0.15 dB
Wire Loss 0.15 dB
Mismatched Gain 7.94 dBd
F/B 30.73 dB
Patterns
Antenna File
Korner 15.10 Yagi Free Space Symmetric 98.000 MHz 18 6063-T832 wires, meters 1 0.0 -1.04 0.0 0.0 1.04 0.0 0.01 1 0.04 -1.04 -0.37 0.04 1.04 -0.37 0.01 1 0.04 -1.04 0.37 0.04 1.04 0.37 0.01 1 0.11 -1.00 -0.73 0.11 1.00 -0.73 0.01 1 0.11 -1.00 0.73 0.11 1.00 0.73 0.01 1 0.575 -0.82 0.0 0.575 0.82 0.0 0.01008 1 0.595 -0.82 0.0 0.595 0.82 0.0 0.01008 1 0.595 -0.82 0.0 0.575 -0.82 0.0 0.01008 1 0.595 0.82 0.0 0.575 0.82 0.0 0.01008 1 0.685 -0.662 0.0 0.685 0.662 0.0 0.01 1 0.79 -0.666 0.0 0.79 0.666 0.0 0.01 1 1.01 -0.657 0.0 1.01 0.657 0.0 0.01 1 1.31 -0.632 0.0 1.31 0.632 0.0 0.01 1 1.605 -0.637 0.0 1.605 0.637 0.0 0.01 1 2.045 -0.625 0.0 2.045 0.625 0.0 0.01 1 2.475 -0.627 0.0 2.475 0.627 0.0 0.01 1 3.01 -0.629 0.0 3.01 0.629 0.0 0.01 1 3.73 -0.581 0.0 3.73 0.581 0.0 0.01 1 source Wire 7, center
The odd driven element diameters are cylindrical equivalents of rectangular conductors. Peter tells me the driven element likely will be constructed with round tubing 0.015 meters in diameter and rectangular connecting straps of smaller equivalent diameter. These changes will make only a small difference in performance. I'll update the results and patterns when the design is finalized, perhaps after a prototype is built and measured SWR is available.
More is here.
Updated August 3, 2007
