Peter Körner in Lund, Sweden, designed this Yagi array. It has a boom length of 5.1 m (201″), 19 elements, five reflectors, a horizontal folded dipole, and uses a halfwave coaxial balun.
Unlike log-Yagis, the 19.3 has no phasing lines that can pick up current from 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 the antenna under test at ground level. The boom is not reinforced.
Here the antenna with boom reinforcement is temporarily installed well above ground for testing with broadcast signals. Peter has some concern that the mast may interact with nearby elements. An offset mast can disrupt fields in a way a centered boom cannot.
This shows how the 15 mm × 5 mm folded dipole conductors join at the ends. The element mount on the right is a repurposed support for 10 mm hydraulic fluid lines.
I modeled the antenna with the AO 9.65 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
88 318+j23 1.10 0.01 0.01 8.77 32.56
89 328+j16 1.11 0.01 0.01 8.94 35.30
90 333+j7 1.11 0.01 0.01 9.11 37.42
91 335-j1 1.12 0.01 0.01 9.29 38.27
92 332-j8 1.11 0.01 0.01 9.47 38.30
93 326-j12 1.10 0.01 0.01 9.66 38.42
94 320-j12 1.08 0.01 0.01 9.84 37.56
95 313-j10 1.05 0.00 0.01 10.02 36.90
96 307-j4 1.03 0.00 0.01 10.20 36.53
97 304+j3 1.02 0.00 0.02 10.36 36.44
98 302+j10 1.04 0.00 0.02 10.50 36.19
99 300+j17 1.06 0.00 0.02 10.62 35.72
100 296+j27 1.09 0.01 0.02 10.70 34.81
101 294+j38 1.14 0.02 0.03 10.74 34.07
102 298+j51 1.18 0.03 0.03 10.71 33.67
103 309+j58 1.21 0.04 0.04 10.62 33.41
104 316+j49 1.18 0.03 0.05 10.48 33.33
105 295+j42 1.15 0.02 0.06 10.27 34.54
106 287+j77 1.30 0.08 0.08 9.97 33.73
107 357+j52 1.27 0.06 0.12 9.77 32.70
108 295+j23 1.08 0.01 0.20 9.50 30.55
This shows how ground proximity affects F/R at 1° elevation angle for various antenna heights.
Körner 19.3 Yagi Free Space Symmetric 88 93 98 103 108 MHz 22 6061-T6 wires, meters h1 = .315 ; reflector heights h2 = .73 rp0 = -.024 ; reflector positions rp1 = -.012 rp2 = .05 de1 = .47 ; driven element positions de2 = .54 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 r0 = 1.003 ; reflector half-lengths r1 = 1.003 r2 = .96 de = .822 ; driven element half-length d1 = .662 ; director half-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 1 rp2 -r2 -h2 rp2 r2 -h2 .01 ; reflectors 1 rp1 -r1 -h1 rp1 r1 -h1 .01 1 rp0 -r0 0 rp0 r0 0 .01 1 rp1 -r1 h1 rp1 r1 h1 .01 1 rp2 -r2 h2 rp2 r2 h2 .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 11.48 mm diameters are cylindrical equivalents of the 15 mm × 5 mm rectangular folded dipole conductors. The 15 mm conductors are short tubes that connect the folded dipole ends.
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
h1 0.0010 0.00 0.01
h2 0.0010 0.00 0.03
rp0 0.0010 0.00 0.01
rp1 0.0010 0.00 0.01
rp2 0.0010 0.00 0.02
de1 0.0010 0.00 0.04
de2 0.0010 0.01 0.04
p1 0.0010 0.01 0.04
p2 0.0010 0.01 0.09
p3 0.0010 0.00 0.05
p4 0.0010 0.00 0.02
p5 0.0010 0.00 0.02
p6 0.0010 0.00 0.03
p7 0.0010 0.00 0.03
p8 0.0010 0.00 0.05
p9 0.0010 0.00 0.04
p10 0.0010 0.00 0.03
p11 0.0010 0.00 0.03
p12 0.0010 0.00 0.06
p13 0.0010 0.00 0.03
r0 0.0005 0.00 0.02
r1 0.0005 0.00 0.03
r2 0.0005 0.00 0.03
de 0.0005 0.00 0.01
d1 0.0005 0.00 0.03
d2 0.0005 0.02 0.16
d3 0.0005 0.01 0.22
d4 0.0005 0.00 0.05
d5 0.0005 0.00 0.05
d6 0.0005 0.00 0.02
d7 0.0005 0.00 0.05
d8 0.0005 0.02 0.15
d9 0.0005 0.00 0.04
d10 0.0005 0.01 0.07
d11 0.0005 0.01 0.07
d12 0.0005 0.01 0.14
d13 0.0005 0.00 0.03
This is the SWR curve measured with an HP 8714B network analyzer.
Peter measured F/B in a city environment. He used a Promax spectrum monitor on horizontally polarized broadcast signals from Sweden and Germany. The following table compares F/B calculated by NEC-2 at 50 segments/ Calculated and measured values may differ due to modeling limitations, construction tolerances, balun or feedline pickup, coupling to nearby conductors, reflection from distant structures, ground effects, interfering signals, or varying signal levels. Peter notes that F/B for the Halmstad signals degraded some 10 dB when he turned the antenna 10°–15° to the west.
This is the view toward Malmö from the antenna location about 20 m above ground.
The opposite direction. I'm surprised Peter was able to measure such high F/B values with so many potential reflections.
A shadow I spotted in one high-resolution skyline photo. Peter secures himself with a safety rope while working on the steeply pitched roof.
This is Peter's 19.3 installed 20 m above ground in Lund, Sweden. The guy lines are nonconductive.
Kay Richter built this 19.3 in Wittenberg, Germany. The plastic end caps may detune the elements and add loss.
Ralf Kronen's 19.3 has too much company in Viersen-Süchteln, Germany.
Thomas Nickel erected this 19.3 in Suhl, Germany.
David Pommerenke used braces instead of a secondary boom for his 19.3 in Rolla, Missouri. The antenna uses half-inch elements with compensated lengths.
Konrad Kosmatka used boom guys for his 19.3 in Plock, Poland. It rotates here. It vibrates here.
Olaf Panke used both boom guys and a secondary boom for his 19.3 in Gülzow, Germany.
Petr Vozár tested his 19.3 at the OK2KJU radio club near Přerov, Czech Republic.
Alan Parysek erected this 19.3 in Skalbmierz, Poland. It rotates here.
This shows Aleksandr Vorona's 19.3 before final installation in Poltava, Ukraine. The plastic end caps may detune the elements and add loss.
Vladimir Doroshenko uses this vertically polarized 19.3 in Dnepropetrovsk, Ukraine. The plastic end caps may detune the elements and add loss.
Mike Fallon added a small vertically polarized Yagi to the boom of his 19.3 in Saltdean, East Sussex, England.
John Bunkfeldt built this well-braced 19.3 in Frankfort, New York.
This 19.3 belongs to Antonín Roll in Mariánské Lázně, Czech Republic.
Jakub Melin tightens a 19.3 in Prague, Czech Republic.
I optimized the 19.3 to keep all backlobes at least 36 dB down over 88–108 MHz. The boom length and element count are unchanged. The reflector boom is slightly shorter and the reflectors are in line. I used a loop-coupled driven element that yields higher forward gain than a horizontal folded dipole and does not require a 300Ω balun. It does need a series capacitor at the 75Ω feedpoint, indicated by the red dot.
I modeled the antenna with the AO 9.65 Antenna Optimizer using 28 analysis segments per conductor halfwave. Forward gain includes mismatch and conductor losses and gain correction by pattern integration. F/R is the ratio of forward power to that of the worst backlobe in the rear half-plane.
Use 15 mm × 5 mm rectangular conductors for the driven element and loop front. Use 15 mm round tubes with a bolt inside for the loop sides. The loop front is 86.2 mm from the driven element. Total loop width is 165.4 mm. Measure dimensions between conductor centerlines. The loop must be in the element plane in front of the driven element. Connect the 75Ω coax shield to one side of the feedpoint gap. Connect the center conductor through an 11 pF capacitor to the other side. The 5% capacitor should have the highest voltage rating available to minimize the chance of failure due to a nearby lightning strike. Keep the gap and all leads as short as possible. Waterproof the connections. Use a current choke at the feedpoint. Read these notes before building anything.
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.
The 19.3 gain curve includes the loss of a halfwave coaxial balun.
Freq Calculated Measured Transmitter Distance Notes
MHz F/B dB F/B dB Location km
87.7 32 42 Halmstad 121
87.9 33 28 Malmö 17
91.2 39 25 Halmstad 121 Possible interference
93.3 41 29 Malmö 17
95.4 44 34 Halmstad 121
97.3 41 37 Halmstad 121
98.0 39 28 Malmö 17
100.6 34 32 Malmö 17
102.0 34 33 Malmö 17
104.8 38 30-33 Marlow 175 Varying signal level, slight interference
105.8 36 31-34 Helpterberg 248 Varying signal level
Gallery
Optimized 19.3
Modeling Results
Frequency Impedance SWR Mismatch Conductor Forward F/R
MHz ohms Loss dB Loss dB Gain dBd dB
88 74.3+j3.3 1.05 0.00 0.02 8.73 36.01
89 76.6-j3.2 1.05 0.00 0.02 8.89 38.62
90 76.7-j7.8 1.11 0.01 0.02 9.04 37.65
91 75.7-j10.8 1.15 0.02 0.02 9.20 36.87
92 75.0-j12.4 1.18 0.03 0.02 9.37 36.41
93 74.3-j13.3 1.20 0.03 0.02 9.54 36.06
94 73.7-j14.1 1.21 0.04 0.02 9.71 36.01
95 72.8-j14.5 1.22 0.04 0.02 9.88 36.10
96 72.3-j14.7 1.22 0.04 0.02 10.04 36.47
97 72.2-j14.6 1.22 0.04 0.02 10.19 36.72
98 72.1-j14.7 1.23 0.05 0.02 10.33 37.17
99 72.1-j15.5 1.24 0.05 0.03 10.43 36.37
100 71.4-j17.1 1.27 0.06 0.03 10.49 36.22
101 69.2-j18.4 1.31 0.08 0.03 10.51 36.84
102 65.3-j17.6 1.33 0.09 0.04 10.47 37.13
103 62.8-j13.1 1.30 0.07 0.05 10.40 36.13
104 65.4-j7.5 1.19 0.03 0.06 10.28 36.00
105 73.5-j8.3 1.12 0.01 0.07 10.09 36.31
106 72.1-j17.5 1.27 0.06 0.09 9.83 36.01
107 64.4-j9.4 1.23 0.04 0.12 9.73 36.00
108 81.1+j16.3 1.25 0.05 0.20 9.62 36.00
Antenna File
Optimized 19.3
Free Space Symmetric
88 94 96 98 100 101 103 104 105 106 107 108 MHz
26 6061-T6 wires, meters
h1 = .28935592 ; reflector heights
h2 = .6861281
rp0 = 0 ; reflector positions
rp1 = 0
rp2 = 0
dep = .44926091 ; driven element position
p1 = .5854994 ; director positions
p2 = .70334772
p3 = .8863801
p4 = 1.0852649
p5 = 1.3765714
p6 = 1.6023626
p7 = 1.9761888
p8 = 2.424466
p9 = 2.8201262
p10 = 3.2340984
p11 = 3.7484955
p12 = 4.3339432
p13 = 5.104
r0 = 1.05974 ; reflector half-lengths
r1 = 1.0085324
r2 = .9689596
de = .7908045 ; driven element half-length
d1 = .6645802 ; director half-lengths
d2 = .66993663
d3 = .6566396
d4 = .6498772
d5 = .63500324
d6 = .62352554
d7 = .6266686
d8 = .6125574
d9 = .59389821
d10 = .61041114
d11 = .6110288
d12 = .598251
d13 = .5361455
w = .082707171 ; loop half-width
s = .05002148 ; loop spacing from first director
p = p1 - s
1 rp2 -r2 -h2 rp2 r2 -h2 .01 ; reflectors
1 rp1 -r1 -h1 rp1 r1 -h1 .01
1 rp0 -r0 0 rp0 r0 0 .01
1 rp1 -r1 h1 rp1 r1 h1 .01
1 rp2 -r2 h2 rp2 r2 h2 .01
1 dep w 0 dep de 0 .01148 ; driven element
1 dep -w 0 dep -de 0 .01148 ; 11.48 mm is the cylindrical
8 dep -w 0 dep w 0 .01148 ; equivalent of 15 mm x 5 mm
8 p -w 0 p w 0 .01148 ; rectangular conductors
4 p w 0 dep w 0 .015
4 p -w 0 dep -w 0 .015
1 p1 -d1 0 p1 -w 0 .01 ; directors
8 p1 -w 0 p1 w 0 .01
1 p1 w 0 p1 d1 0 .01
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 9, center
1 load
c = 11.196933 ; series feedpoint capacitor
Wire 9, center c pF
Construction
Sensitivity Analysis
Symbol Tol Gain F/R
h1 0.0010 0.00 0.01
h2 0.0010 0.00 0.06
rp0 0.0010 0.00 0.01
rp1 0.0010 0.00 0.02
rp2 0.0010 0.00 0.04
dep 0.0010 0.01 0.10
p1 0.0010 0.01 0.15
p2 0.0010 0.01 0.22
p3 0.0010 0.00 0.08
p4 0.0010 0.00 0.06
p5 0.0010 0.00 0.03
p6 0.0010 0.00 0.05
p7 0.0010 0.00 0.06
p8 0.0010 0.00 0.07
p9 0.0010 0.00 0.07
p10 0.0010 0.00 0.10
p11 0.0010 0.00 0.06
p12 0.0010 0.00 0.08
p13 0.0010 0.00 0.05
r0 0.0005 0.00 0.02
r1 0.0005 0.00 0.05
r2 0.0005 0.00 0.04
de 0.0005 0.00 0.03
d1 0.0010 0.01 0.51
d2 0.0005 0.05 1.25
d3 0.0005 0.02 0.52
d4 0.0005 0.01 0.19
d5 0.0005 0.01 0.12
d6 0.0005 0.00 0.05
d7 0.0005 0.01 0.30
d8 0.0005 0.00 0.36
d9 0.0005 0.01 0.08
d10 0.0005 0.00 0.40
d11 0.0005 0.01 0.58
d12 0.0005 0.00 0.68
d13 0.0005 0.00 0.16
w 0.0005 0.01 0.00
s 0.0010 0.02 0.03
c 1.1197 0.14 0.00
Performance Comparison
October 5, 2021
88–108 MHz