Körner 9.2

Peter Körner in Lund, Sweden, designed this Yagi array. It has a boom length of 2.05 m (81″), nine elements, three reflectors, and a horizontal folded dipole.

Unlike log-Yagis, the 9.2 has no phasing lines that can induce current in the boom and degrade the pattern. The red dot indicates the 300Ω feedpoint.

The horizontal folded dipole 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. The image shows a commercial version of the antenna available here.

Modeling Results

I modeled the antenna with the AO 9.57 Antenna Optimizer program using 28 analysis segments per conductor 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     290 + j5     1.04     0.00      0.01      6.19     27.45
    89     297 - j2     1.01     0.00      0.01      6.24     30.39
    90     302 - j9     1.03     0.00      0.01      6.31     33.65
    91     303 - j15    1.05     0.00      0.01      6.38     34.04
    92     302 - j20    1.07     0.00      0.01      6.46     33.98
    93     299 - j23    1.08     0.01      0.01      6.55     33.12
    94     294 - j24    1.09     0.01      0.01      6.64     32.23
    95     289 - j23    1.09     0.01      0.01      6.74     31.58
    96     283 - j19    1.09     0.01      0.01      6.84     31.13
    97     278 - j15    1.10     0.01      0.01      6.95     30.84
    98     273 - j10    1.11     0.01      0.01      7.05     30.73
    99     268 - j4     1.12     0.01      0.01      7.16     30.71
   100     263 + j3     1.14     0.02      0.01      7.26     30.62
   101     258 + j11    1.17     0.03      0.01      7.35     30.71
   102     253 + j20    1.21     0.04      0.01      7.41     30.61
   103     247 + j28    1.24     0.05      0.02      7.46     30.43
   104     241 + j33    1.29     0.07      0.02      7.46     29.87
   105     229 + j42    1.37     0.11      0.03      7.39     29.17
   106     213 + j55    1.50     0.18      0.03      7.20     28.08
   107     195 + j79    1.71     0.31      0.04      6.82     26.81
   108     191 + j120   1.94     0.47      0.06      6.23     25.48

Ground Effects

This shows how ground proximity affects F/R at 1° elevation angle for various antenna heights.

Antenna File

Körner 9.2
Free Space Symmetric
98 MHz
12 6063-T832 wires, meters
z = 0.53 			; reflector height
r0 = 0.982			; reflector half-lengths
r1 = 0.911			
rp = 0.05			; outer reflector positions
de = 0.8			; driven element half-length
d1 = 0.657			; director half-lengths
d2 = 0.657
d3 = 0.647
d4 = 0.621
d5 = 0.562
de1 = 0.44			; driven element positions
de2 = 0.54
d1p = 0.65			; director positions
d2p = 0.79
d3p = 1.07
d4p = 1.47
d5p = 2.05
1     rp  -r1  z    rp  r1  z   .012
1      0  -r0  0     0  r0  0   .012
1     rp  -r1 -z    rp  r1 -z   .012
1    de1  -de  0   de1  de  0   .012
1    de2  -de  0   de2  de  0   .012
1    de1   de  0   de2  de  0   .012
1    de1  -de  0   de2 -de  0   .012
1    d1p  -d1  0   d1p  d1  0   .012
1    d2p  -d2  0   d2p  d2  0   .012
1    d3p  -d3  0   d3p  d3  0   .012
1    d4p  -d4  0   d4p  d4  0   .012
1    d5p  -d5  0   d5p  d5  0   .012
1 source
Wire 5, center

Sensitivity Analysis

The following table shows the largest performance degradation over 88, 93, 98, 103, and 108 MHz in dB when altering a symbol value by Tol.

Symbol      Tol   Gain    F/R
     z   0.0010   0.00   0.04
    r0   0.0005   0.00   0.02
    r1   0.0005   0.00   0.09
    rp   0.0010   0.00   0.03
    de   0.0005   0.00   0.02
    d1   0.0005   0.03   0.04
    d2   0.0005   0.03   0.11
    d3   0.0005   0.08   0.13
    d4   0.0005   0.02   0.13
    d5   0.0005   0.00   0.03
   de1   0.0010   0.00   0.03
   de2   0.0010   0.01   0.04
   d1p   0.0010   0.01   0.04
   d2p   0.0010   0.01   0.06
   d3p   0.0010   0.01   0.06
   d4p   0.0010   0.00   0.02
   d5p   0.0010   0.00   0.03

Gallery

John Faulkner erected this 9.2 in Skegness, Lincolnshire, England. It rotates in azimuth and polarization here.

This is Balazs Benko's 9.2 in Budapest, Hungary.

Petr Vozár erected this 9.2 near Javornik, Czechia.

This shows Georgiy Markiev's vertical stack in Petrozavodsk, Russia. The antenna came down in a wind storm.

Paul Z. in White Plains, New York, had this 9.2 shipped from Germany.

Glenn Davis built this 9.2 with spliced elements and custom element mounts in Hutto, Texas.


November 21, 201688–108 MHz