Single Yagi

I used the AO 9.65 Antenna Optimizer to design this Yagi for DAB/DAB+ reception on Band III (174–240 MHz). The antenna has two reflectors, nine elements total, and a boom length of 1.3 m. The red dot is the 50Ω feedpoint.

Modeling Results

I optimized the design for maximum forward gain without regard for the pattern. Calculated performance is for 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 
   174     44.9-j15.9   1.42     0.13      0.01      6.41       9.08
   177     60.0-j10.4   1.30     0.08      0.01      6.62      11.57
   180     73.3-j10.9   1.53     0.19      0.01      6.56      12.73
   183     82.0-j14.6   1.72     0.32      0.01      6.47      12.67
   186     85.8-j18.6   1.83     0.39      0.01      6.42      12.18
   189     86.9-j20.8   1.88     0.43      0.01      6.42      11.70
   192     86.1-j20.9   1.87     0.42      0.01      6.49      11.32
   195     85.2-j19.2   1.83     0.39      0.01      6.61      11.07
   198     84.7-j16.4   1.79     0.36      0.01      6.75      10.93
   201     85.1-j13.0   1.76     0.34      0.01      6.91      10.84
   204     86.7-j10.1   1.77     0.35      0.01      7.08      10.83
   207     88.5-j8.5    1.79     0.37      0.01      7.25      10.91
   210     89.7-j9.0    1.82     0.38      0.01      7.44      11.10
   213     88.2-j11.9   1.81     0.38      0.01      7.67      11.30
   216     82.1-j14.5   1.72     0.32      0.01      7.95      11.55
   219     71.2-j13.2   1.52     0.19      0.01      8.30      11.90
   222     59.4-j5.0    1.21     0.04      0.02      8.65      12.10
   225     51.6+j9.7    1.21     0.04      0.02      8.84      12.47
   228     51.9+j28.4   1.74     0.33      0.03      8.71      13.08
   231     71.4+j44.3   2.23     0.68      0.03      8.42      14.16
   234     94.3+j4.5    1.89     0.43      0.05      8.51      13.95
   237     38.8+j3.2    1.30     0.07      0.08      8.45      12.65
   240     50.9+j0.7    1.02     0.00      0.17      8.00      12.03

Antenna File

DAB Yagi
Free Space
174 185 195 205 215 225 230 234 238 240 MHz
9 6063-T832 wires, mm
r = 413.46056			; element half-lengths
de = 378.15444
d1 = 299.392
d2 = 292.918
d3 = 282.92443
d4 = 270.88173
d5 = 274.0881
d6 = 273.67305
rp = 0				; element positions
dep = 260.5823
d1p = 293.695
d2p = 389.2611
d3p = 598.53183
d4p = 834.04703
d5p = 1043.5107
d6p = 1300
s = 290.96865			; reflector half-spacing
1   rp  s  -r   rp  s  r   10
1   rp -s  -r   rp -s  r   10
1   dep 0 -de   dep 0 de   10
1   d1p 0 -d1   d1p 0 d1   10
1   d2p 0 -d2   d2p 0 d2   10
1   d3p 0 -d3   d3p 0 d3   10
1   d4p 0 -d4   d4p 0 d4   10
1   d5p 0 -d5   d5p 0 d5   10
1   d6p 0 -d6   d6p 0 d6   10
1 source
Wire 3, center

Construction

Use 10 mm aluminum tubing supported by insulated mounts. Symbols r, de, and d1-d6 are element half-lengths (center to tip), rp, dep, and d1p-d6p are element positions, and s is the reflector half-spacing. Rear-mount the antenna with the mast 100 mm behind the reflector plane. Route the 50Ω coax to the rear and down the mast. Install at least one ferrite choke at the feedpoint.

Sensitivity Analysis

The following table shows the largest performance degradation over the antenna file frequencies in dB when altering a single dimension by Tol.

Symbol      Tol   Gain    F/R
     r   0.5000   0.01   0.15
    de   0.5000   0.02   0.01
    d1   0.5000   0.10   0.08
    d2   0.5000   0.12   0.43
    d3   0.5000   0.10   0.22
    d4   0.5000   0.03   0.05
    d5   0.5000   0.05   0.20
    d6   0.5000   0.04   0.11
    rp   1.0000   0.00   0.01
   dep   1.0000   0.06   0.05
   d1p   1.0000   0.07   0.08
   d2p   1.0000   0.03   0.07
   d3p   1.0000   0.02   0.02
   d4p   1.0000   0.01   0.03
   d5p   1.0000   0.01   0.05
   d6p   1.0000   0.01   0.04
     s   1.0000   0.00   0.02

Stacked Yagis

This array has 22 elements. Boom length is 2.55 m, stacking distance is 0.92 m, and the reflectors span 1.25 m. The reflectors have unequal but symmetrical lengths and offsets.

Modeling Results

I used AO 9.63 to optimize both forward gain and the pattern, including suppression of secondary forward lobes. Calculated performance is for 28 analysis segments per conductor halfwave. Forward gain includes mismatch and conductor losses, but not stacking cable or power combiner 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 
   174     47.3-j16.4   1.40     0.12      0.01      9.41      20.00
   177     56.5-j10.4   1.26     0.06      0.01      9.60      25.31
   180     65.6-j6.5    1.34     0.09      0.01      9.67      24.68
   183     74.4-j4.4    1.50     0.18      0.01      9.70      24.12
   186     81.6-j4.4    1.64     0.26      0.01      9.73      23.58
   189     86.8-j5.7    1.75     0.33      0.01      9.79      22.44
   192     89.9-j7.4    1.81     0.38      0.01      9.88      21.68
   195     90.9-j8.6    1.84     0.40      0.01     10.01      21.18
   198     91.0-j8.9    1.84     0.40      0.01     10.17      20.98
   201     90.1-j8.1    1.82     0.39      0.01     10.37      21.02
   204     89.3-j6.6    1.80     0.37      0.01     10.59      21.03
   207     88.5-j4.9    1.78     0.35      0.01     10.82      20.68
   210     87.3-j3.7    1.75     0.34      0.01     11.07      20.46
   213     85.6-j2.8    1.72     0.31      0.01     11.35      20.07
   216     81.8-j1.2    1.64     0.26      0.01     11.67      19.82
   219     76.8+j2.3    1.54     0.20      0.01     12.01      19.91
   222     73.1+j8.1    1.50     0.17      0.02     12.32      19.98
   225     73.2+j14.3   1.56     0.22      0.02     12.57      20.01
   228     75.8+j14.0   1.60     0.24      0.03     12.81      20.60
   231     65.9+j6.3    1.35     0.10      0.04     13.14      22.56
   234     48.6+j18.3   1.45     0.15      0.06     13.12      20.50
   237     63.2+j25.1   1.65     0.27      0.09     12.81      20.29
   240     47.4+j4.3    1.11     0.01      0.26     12.54      19.97

Antenna File

Stacked DAB Yagis
Free Space Symmetrix
174 190 205 214 220 227 235 238 239 240 MHz
11 6063-T832 wires, mm
ri = 450.4879		; element half-lengths
ro = 429.8947
de = 387.8235
d1 = 301.6371
d2 = 295.2137
d3 = 284.4728
d4 = 278.1006
d5 = 270.8748
d6 = 269.2393
d7 = 265.1729
d8 = 257.9645
dep = 259.0257		; element positions
d1p = 289.2319
d2p = 362.3309
d3p = 566.4574
d4p = 879.4938
d5p = 1271.861
d6p = 1678.719
d7p = 2147.34
d8p = 2548.055
o = 163.84		; outer reflector offset
i = 278.1921		; inner reflector offset
sp = 461.1318		; boom half-spacing
shift y sp
1    0 -i -ri    0 -i ri   10
1    0  o -ro    0  o ro   10
1   dep 0 -de   dep 0 de   10
1   d1p 0 -d1   d1p 0 d1   10
1   d2p 0 -d2   d2p 0 d2   10
1   d3p 0 -d3   d3p 0 d3   10
1   d4p 0 -d4   d4p 0 d4   10
1   d5p 0 -d5   d5p 0 d5   10
1   d6p 0 -d6   d6p 0 d6   10
1   d7p 0 -d7   d7p 0 d7   10
1   d8p 0 -d8   d8p 0 d8   10
1 source
Wire 3, center

Construction

Use 10 mm aluminum tubing supported by insulated mounts. Rear-mount the antenna if possible. Otherwise use a nonconductive mast section in the vicinity of the antenna. Use at least one ferrite choke at each feedpoint and connect 50Ω cables of equal length to a 50Ω hybrid power combiner. For lower loss, replace the hybrid with two 75Ω cables, each an electrical quarter-wavelength long at 204 MHz (305 mm for Belden 1530A) joined with a junction splitter. SWR for this combiner will be 1.25 maximum and total loss 0.1 dB maximum over 174–240 MHz. Use 50Ω coax from the end of the 75Ω cables to the antenna feedpoints and from combiner to the receiver.

To increase forward gain 3.0 dB with substantially the same pattern, stack two of the 22-element arrays vertically with their booms 2.5 meters apart.

Sensitivity Analysis

The following table shows the largest performance degradation over the antenna file frequencies in dB when altering a single dimension by Tol.

Symbol      Tol   Gain    F/R
    ri   0.5000   0.00   0.08
    ro   0.5000   0.00   0.18
    de   0.5000   0.01   0.01
    d1   0.5000   0.10   0.08
    d2   0.5000   0.17   0.89
    d3   0.5000   0.10   0.45
    d4   0.5000   0.08   1.27
    d5   0.5000   0.07   0.44
    d6   0.5000   0.07   0.69
    d7   0.5000   0.02   0.28
    d8   0.5000   0.01   0.18
   dep   1.0000   0.06   0.10
   d1p   1.0000   0.07   0.12
   d2p   1.0000   0.03   0.16
   d3p   1.0000   0.01   0.12
   d4p   1.0000   0.01   0.11
   d5p   1.0000   0.01   0.07
   d6p   1.0000   0.01   0.12
   d7p   1.0000   0.01   0.07
   d8p   1.0000   0.00   0.11
     o   1.0000   0.00   0.02
     i   1.0000   0.00   0.01
    sp   1.0000   0.00   0.08

Performance Comparison

Gallery

Petr Vozár erected this 22-element stack at Přerov, Czech Republic.


May 23, 201888–108 MHz