Antenna Performance Specialties APS-13

The Antenna Performance Specialties APS-13 is a log-Yagi array with 13 elements on a 197″ boom. Five of the elements are driven. A shorted phasing line terminates at a passive reflector.

I modeled the antenna with the AO 9.53 Antenna Optimizer. This image shows the antenna geometry.

This shows phasing line and feedpoint detail. Blue dots mark analysis segments. The red dot is the feedpoint.

Feedpoint

Normally I jumper a wire across the feedpoint terminals and place a source at its center. This model is unrealistic for the APS-13 because the boom is between the terminals. The supplied balun has leads approximately 4″ long. I model their geometry instead. The resulting inductive reactance alters SWR, mismatch loss, and forward gain.

Modeling Results

Calculated performance is for 28 analysis segments per conductor halfwave with additional segments for the phasing lines. 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     233 + j145   1.81     0.38      0.11      8.47     23.11
    89     176 + j134   2.17     0.63      0.08      8.32     27.06
    90     170 + j159   2.41     0.81      0.07      8.19     29.09
    91     187 + j179   2.38     0.79      0.06      8.25     29.98
    92     211 + j190   2.25     0.69      0.06      8.39     30.58
    93     237 + j189   2.07     0.57      0.05      8.58     31.73
    94     258 + j180   1.92     0.45      0.05      8.76     32.31
    95     273 + j167   1.79     0.37      0.04      8.93     33.11
    96     281 + j155   1.70     0.30      0.04      9.09     34.24
    97     287 + j145   1.63     0.26      0.04      9.25     35.52
    98     291 + j135   1.57     0.22      0.04      9.41     36.97
    99     292 + j125   1.52     0.19      0.04      9.58     37.27
   100     288 + j117   1.49     0.17      0.04      9.74     34.01
   101     280 + j112   1.48     0.16      0.04      9.89     31.99
   102     265 + j115   1.53     0.19      0.04     10.00     30.98
   103     252 + j130   1.65     0.27      0.04     10.05     30.58
   104     246 + j158   1.83     0.39      0.05     10.03     30.66
   105     255 + j191   2.01     0.52      0.05      9.95     31.14
   106     282 + j215   2.07     0.56      0.06      9.86     31.15
   107     292 + j206   1.98     0.50      0.07      9.73     30.36
   108     224 + j230   2.47     0.86      0.10      8.94     30.61

Antenna File

APS-13
Free Space
98.000 MHz
75 6063-T832 wires, inches
rp = 0				; element positions
e1p = 9.25
e2p = e1p + 11.625
e3p = e2p + 11.625
e4p = e3p + 11.625
e5p = e4p + 11.625
d1p = e5p - 4
d2p = e5p + 13.625
d3p = d2p + 20.625
d4p = d3p + 23
d5p = d4p + 25.75
d6p = d5p + 27
d7p = d6p + 31
d = .11                         ; phasing-line diameter
r = 1.875 / 2                   ; spacing of rivets on insulated elements
x1 = 3                          ; x at first phasing-line bend
e = e1p - rp			; phasing line length   (R-DE1)
s2 = .5 / 2                     ; phasing-line half-spacing at crossover point
x2 = 3.125                      ; x at second bend
x3 = e - x2                     ; x at third bend
x4 = e - x1                     ; x at fourth bend
e2 = e / 2                      ; half of element spacing
y1 = r * (1 - x1 / e2)          ; y at first bend
y2 = r * (1 - x2 / e2)          ; y at second bend
f = e2p - e1p			; phasing line length   (DE1-DE2 ... DE4-DE5)
s1 = .375 / 2                   ; phasing-line half-spacing at crossover point
w2 = 3.4375                     ; x at second bend
x5 = f - w2                     ; x at third bend
x6 = f - x1                     ; x at fourth bend
f2 = f / 2                      ; half of element spacing
y5 = r * (1 - x1 / f2)          ; y at first bend
y6 = r * (1 - w2 / f2)          ; y at second bend
s = .3125 / 2			; feedpoint half-spacing
b = .75				; feedpoint bolt length
v = b + 4			; feedpoint
1    rp   -32.6753   0    rp   -1.25      0    0.3773
1    rp   -1.25      0    rp    1.25      0    0.3773
1    rp    1.25      0    rp    32.6753   0    0.3773
1    e1p  -29.75     0    e1p  -r         0    0.3750
1    e1p   r         0    e1p   29.75     0    0.3750
1    e2p  -28.625    0    e2p  -r         0    0.3750
1    e2p   r         0    e2p   28.625    0    0.3750
1    e3p  -26.25     0    e3p  -r         0    0.3750
1    e3p   r         0    e3p   26.25     0    0.3750
1    e4p  -25.125    0    e4p  -r         0    0.3750
1    e4p   r         0    e4p   25.125    0    0.3750
1    d1p  -25.5155  -2    d1p   25.5155  -2    0.3798
1    e5p  -17        0    e5p  -r         0    0.3750
1    e5p  -r         0    e5p  -r        -b    0.1250   zinc
1    e5p   r        -b    e5p   s        -v      #16    copper
1    e5p  -s        -v    e5p   s        -v      #16    copper
1    e5p  -r        -b    e5p  -s        -v      #16    copper
1    e5p   r         0    e5p   r        -b    0.1250	zinc
1    e5p   r         0    e5p   17        0    0.3750
1    d2p  -25.0125   0    d2p   25.0125   0    0.3801
1    d3p  -24.5094   0    d3p   24.5094   0    0.3804
1    d4p  -24.3836   0    d4p   24.3836   0    0.3805
1    d5p  -24.0062   0    d5p   24.0062   0    0.3807
1    d6p  -23.3771   0    d6p   23.3771   0    0.3811
1    d7p  -21.8665   0    d7p   21.8665   0    0.3823
4   0   1.25  0     x1   y1   0    d
1   x1   y1   0     x2   y2  -s2   d
6   x2   y2  -s2    x3  -y2  -s2   d
1   x3  -y2  -s2    x4  -y1   0    d
4   x4  -y1   0     e   -r    0    d
4   0  -1.25  0     x1  -y1   0    d
1   x1  -y1   0     x2  -y2   s2   d
6   x2  -y2   s2    x3   y2   s2   d
1   x3   y2   s2    x4   y1   0    d
4   x4   y1   0     e     r   0    d
shift x e1p
4   0     r   0     x1   y5   0    d
1   x1   y5   0     w2   y6  -s1   d
10  w2   y6  -s1    x5  -y6  -s1   d
1   x5  -y6  -s1    x6  -y5   0    d
4   x6  -y5   0     f    -r   0    d
4   0    -r   0     x1  -y5   0    d
1   x1  -y5   0     w2  -y6   s1   d
10  w2  -y6   s1    x5   y6   s1   d
1   x5   y6   s1    x6   y5   0    d
4   x6   y5   0     f     r   0    d
shift x e2p
4   0     r   0     x1   y5   0    d
1   x1   y5   0     w2   y6  -s1   d
10  w2   y6  -s1    x5  -y6  -s1   d
1   x5  -y6  -s1    x6  -y5   0    d
4   x6  -y5   0     f    -r   0    d
4   0    -r   0     x1  -y5   0    d
1   x1  -y5   0     w2  -y6   s1   d
10  w2  -y6   s1    x5   y6   s1   d
1   x5   y6   s1    x6   y5   0    d
4   x6   y5   0     f     r   0    d
shift x e3p
4   0     r   0     x1   y5   0    d
1   x1   y5   0     w2   y6  -s1   d
10  w2   y6  -s1    x5  -y6  -s1   d
1   x5  -y6  -s1    x6  -y5   0    d
4   x6  -y5   0     f    -r   0    d
4   0    -r   0     x1  -y5   0    d
1   x1  -y5   0     w2  -y6   s1   d
10  w2  -y6   s1    x5   y6   s1   d
1   x5   y6   s1    x6   y5   0    d
4   x6   y5   0     f     r   0    d
shift x e4p
4   0     r   0     x1   y5   0    d
1   x1   y5   0     w2   y6  -s1   d
10  w2   y6  -s1    x5  -y6  -s1   d
1   x5  -y6  -s1    x6  -y5   0    d
4   x6  -y5   0     f    -r   0    d
4   0    -r   0     x1  -y5   0    d
1   x1  -y5   0     w2  -y6   s1   d
10  w2  -y6   s1    x5   y6   s1   d
1   x5   y6   s1    x6   y5   0    d
4   x6   y5   0     f     r   0    d
1 source
Wire 16, center

I used the YO 7.70 Yagi Optimizer program to calculate the effect of the mounting
brackets on the uninsulated elements. The equivalent elements are shorter and slightly
thicker than the actual elements.

May 30, 201588108 MHz