Antenna Performance Specialities APS-13

The Antenna Performance Specialties APS-13 is an outdoor receiving antenna for the FM broadcast band. It is a Log-Yagi array with thirteen elements on a 200" boom. Five of the elements are driven. A shorted transmission line terminates at a passive reflector.

I modeled the antenna with the AO-Pro 7.03 Antenna Optimizer program. This image shows the antenna geometry.

This image shows segmentation detail for the phasing lines that interconnect the driven elements.

Modeling Results

Below are calculated performance figures for a segmentation density of 80 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. Balun loss is not included.
88.000 MHz:   Impedance         182 + j88 ohms
              SWR                 1.86
              Mismatch Loss       0.41 dB
              Wire Loss           0.10 dB
              Mismatched Gain     8.44 dBd
              F/B                31.77 dB

90.000 MHz:   Impedance         160 + j70 ohms
              SWR                 2.01
              Mismatch Loss       0.52 dB
              Wire Loss           0.06 dB
              Mismatched Gain     8.51 dBd
              F/B                29.99 dB

92.000 MHz:   Impedance         190 + j86 ohms
              SWR                 1.78
              Mismatch Loss       0.36 dB
              Wire Loss           0.05 dB
              Mismatched Gain     8.80 dBd
              F/B                30.49 dB

94.000 MHz:   Impedance         223 + j75 ohms
              SWR                 1.51
              Mismatch Loss       0.18 dB
              Wire Loss           0.04 dB
              Mismatched Gain     9.12 dBd
              F/B                33.64 dB

96.000 MHz:   Impedance         236 + j55 ohms
              SWR                 1.37
              Mismatch Loss       0.11 dB
              Wire Loss           0.04 dB
              Mismatched Gain     9.39 dBd
              F/B                41.41 dB

98.000 MHz:   Impedance         237 + j42 ohms
              SWR                 1.33
              Mismatch Loss       0.09 dB
              Wire Loss           0.03 dB
              Mismatched Gain     9.66 dBd
              F/B                47.70 dB

100.000 MHz:  Impedance         231 + j35 ohms
              SWR                 1.34
              Mismatch Loss       0.09 dB
              Wire Loss           0.03 dB
              Mismatched Gain     9.93 dBd
              F/B                37.43 dB

102.000 MHz:  Impedance         214 + j44 ohms
              SWR                 1.46
              Mismatch Loss       0.16 dB
              Wire Loss           0.04 dB
              Mismatched Gain    10.14 dBd
              F/B                36.11 dB

104.000 MHz:  Impedance         213 + j85 ohms
              SWR                 1.61
              Mismatch Loss       0.24 dB
              Wire Loss           0.04 dB
              Mismatched Gain    10.24 dBd
              F/B                39.37 dB

106.000 MHz:  Impedance         263 + j85 ohms
              SWR                 1.39
              Mismatch Loss       0.12 dB
              Wire Loss           0.06 dB
              Mismatched Gain    10.24 dBd
              F/B                32.27 dB

108.000 MHz:  Impedance         116 + j112 ohms
              SWR                 3.00
              Mismatch Loss       1.25 dB
              Wire Loss           0.13 dB
              Mismatched Gain     8.19 dBd
              F/B                29.80 dB

Performance

Calculated

Average gain: 9.33 dBd (balun loss not included)
Average F/B: 35.45 dB
Specified
Average gain: 10 dBd (balun included with antenna; loss not specified)
Average F/B:  30 dB
Ken Wetzel measured the loss of an APS balun as approximately 0.75 dB. Subtract this amount from the calculated gain figures if you use a 75-ohm feedline.

Patterns

Antenna File

APS-13
Free Space
98.000 MHz
71 6063-T832 wires, inches
e = 98.4375-89.1875		; element spacing 9.25
f = 89.1875-77.5625		; element spacing 11.625
g = 77.5625-66.0625		; element spacing 11.5
s2 = .71875 / 2		; phasing-line half-spacing at crossover point (first)
s1 = .375 / 2  		; phasing-line half-spacing at crossover point (others)
d = .11    			; phasing-line diameter
r = 1.875 / 2		; spacing of rivets on insulated elements
x1 = 3.375			; x at first phasing-line kink
x2 = 3.875			; x at second kink
x3 = e - x2			; x at third kink
x4 = e - x1			; x at fourth kink
x5 = f - x2			; x at third kink
x6 = f - x1			; x at fourth kink
x7 = g - x2			; x at third kink
x8 = g - x1			; x at fourth kink
e2 = e / 2			; half of element spacing
y1 = r * (1 - x1 / e2)	; y at first kink
y2 = r * (1 - x2 / e2)	; y at second kink
f2 = f / 2			; half of element spacing
y5 = r * (1 - x1 / f2)	; y at first kink
y6 = r * (1 - x2 / f2)	; y at second kink
g2 = g / 2			; half of element spacing
y7 = r * (1 - x1 / g2)	; y at first kink
y8 = r * (1 - x2 / g2)	; y at second kink
1    -42.8125  -r          0.0000    -42.8125   r          0.0000    0.3750
1    -98.4375  -r          0.0000    -98.4375   r          0.0000    0.3771
1    -98.4375  -32.9109    0.0000    -98.4375  -r          0.0000    0.3771
1    -98.4375   r          0.0000    -98.4375   32.9109    0.0000    0.3771
1    -89.1875  -29.5625    0.0000    -89.1875  -r          0.0000    0.3750
1    -89.1875   r          0.0000    -89.1875   29.5625    0.0000    0.3750
1    -77.5625  -28.4375    0.0000    -77.5625  -r          0.0000    0.3750
1    -77.5625   r          0.0000    -77.5625   28.4375    0.0000    0.3750
1    -66.0625  -26.1875    0.0000    -66.0625  -r          0.0000    0.3750
1    -66.0625   r          0.0000    -66.0625   26.1875    0.0000    0.3750
1    -54.4375  -24.9375    0.0000    -54.4375  -r          0.0000    0.3750
1    -54.4375   r          0.0000    -54.4375   24.9375    0.0000    0.3750
1    -46.6875  -25.5074   -1.8750    -46.6875   25.5074   -1.8750    0.3792
1    -42.8125  -16.9375    0.0000    -42.8125  -r          0.0000    0.3750
1    -42.8125   r          0.0000    -42.8125   16.9375    0.0000    0.3750
1    -29.1875  -25.1307    0.0000    -29.1875   25.1307    0.0000    0.3794
1     -8.5625  -24.5026    0.0000     -8.5625   24.5026    0.0000    0.3797
1     14.4375  -24.5026    0.0000     14.4375   24.5026    0.0000    0.3797
1     40.4375  -24.0001    0.0000     40.4375   24.0001    0.0000    0.3799
1     67.4375  -23.4975    0.0000     67.4375   23.4975    0.0000    0.3802
1     98.4375  -21.9892    0.0000     98.4375   21.9892    0.0000    0.3812
shift x -98.4375
1      0         r        0          x1        y1         0         d
1      x1       y1        0          x2        y2        -s2        d
1      x2       y2       -s2         x3        -y2        -s2        d
1      x3       -y2       -s2         x4        -y1         0         d
1      x4       -y1        0          e         -r         0         d
1      0        -r        0          x1        -y1        0         d
1      x1      -y1        0          x2        -y2        s2        d
1      x2      -y2        s2         x3        y2        s2        d
1      x3      y2        s2         x4        y1        0         d
1      x4      y1        0          e          r         0         d
shift x -89.1875
1      0         r        0          x1        y5         0         d
1      x1       y5        0          x2        y6        -s1        d
1      x2       y6       -s1         x5        -y6        -s1        d
1      x5       -y6       -s1         x6        -y5         0         d
1      x6       -y5        0          f         -r         0         d
1      0        -r        0          x1        -y5        0         d
1      x1      -y5        0          x2        -y6        s1        d
1      x2      -y6        s1         x5        y6        s1        d
1      x5      y6        s1         x6        y5        0         d
1      x6      y5        0          f          r         0         d
shift x -77.5625
1      0         r        0          x1        y7         0         d
1      x1       y7        0          x2        y8        -s1        d
1      x2       y8       -s1         x7        -y8        -s1        d
1      x7       -y8       -s1         x8        -y7         0         d
1      x8       -y7        0          g         -r         0         d
1      0        -r        0          x1        -y7        0         d
1      x1      -y7        0          x2        -y8        s1        d
1      x2      -y8        s1         x7        y8        s1        d
1      x7      y8        s1         x8        y7        0         d
1      x8      y7        0          g          r         0         d
shift x -66.0625
1      0         r        0          x1        y5         0         d
1      x1       y5        0          x2        y6        -s1        d
1      x2       y6       -s1         x5        -y6        -s1        d
1      x5       -y6       -s1         x6        -y5         0         d
1      x6       -y5        0          f         -r         0         d
1      0        -r        0          x1        -y5        0         d
1      x1      -y5        0          x2        -y6        s1        d
1      x2      -y6        s1         x5        y6        s1        d
1      x5      y6        s1         x6        y5        0         d
1      x6      y5        0          f          r         0         d
shift x -54.4375
1      0         r        0          x1        y5         0         d
1      x1       y5        0          x2        y6        -s1        d
1      x2       y6       -s1         x5        -y6        -s1        d
1      x5       -y6       -s1         x6        -y5         0         d
1      x6       -y5        0          f         -r         0         d
1      0        -r        0          x1        -y5        0         d
1      x1      -y5        0          x2        -y6        s1        d
1      x2      -y6        s1         x5        y6        s1        d
1      x5      y6        s1         x6        y5        0         d
1      x6      y5        0          f          r         0         d
1 source
Wire 1, center

Disable bent-wire correction and use 80 segments/halfwave.
I used the YO 7.65 Yagi Optimizer program to calculate the effect of the mounting brackets on the uninsulated elements. The equivalent elements are shorter and thicker than the actual elements. Feedpoint detail was not modeled.


More is here.

Updated July 8, 2007