The Antenna Performance Specialties APS-13 is a Log-Yagi array with 13 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 9.50 Antenna Optimizer program. This image shows the antenna geometry.
This shows segmentation detail for the phasing lines that interconnect the driven elements. Blue dots mark segment boundaries. The red dot is the feedpoint.
Calculated performance figures are for a segmentation density of 50 segments per 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. Balun loss is not modeled; subtract 0.75 dB from the gain figures to account for it.
Frequency Impedance SWR Mismatch Conductor Forward F/R
MHz ohms Loss dB Loss dB Gain dBd dB
88 191 + j84 1.76 0.35 0.13 8.52 24.31
89 153 + j70 2.10 0.59 0.10 8.37 27.94
90 148 + j89 2.25 0.70 0.08 8.31 29.55
91 162 + j106 2.17 0.63 0.07 8.42 30.22
92 182 + j116 2.00 0.51 0.06 8.59 30.95
93 204 + j116 1.82 0.39 0.06 8.77 31.95
94 222 + j110 1.68 0.29 0.05 8.94 32.48
95 235 + j101 1.57 0.22 0.05 9.10 33.20
96 243 + j91 1.49 0.17 0.05 9.24 34.28
97 249 + j83 1.43 0.14 0.04 9.39 35.45
98 255 + j77 1.38 0.11 0.04 9.54 37.31
99 257 + j68 1.34 0.09 0.04 9.69 36.85
100 254 + j60 1.31 0.08 0.04 9.85 33.84
101 245 + j55 1.33 0.09 0.04 9.98 32.04
102 232 + j57 1.40 0.12 0.04 10.09 31.05
103 218 + j70 1.52 0.19 0.04 10.14 30.67
104 210 + j93 1.67 0.28 0.05 10.14 30.90
105 215 + j123 1.79 0.36 0.06 10.09 31.37
106 234 + j142 1.79 0.36 0.07 10.01 31.11
107 233 + j131 1.73 0.32 0.08 9.81 30.20
108 161 + j159 2.53 0.90 0.12 8.72 31.15
The unequal heights of the phasing lines in the crossover regions can induce current in the boom. I modeled the 1″ × 1″ square boom as a 1.18″ round conductor at the boom axis. It connects to the uninsulated parasitic elements. This model may not be entirely realistic. The phasing lines may be closer to the boom surface than the algorithm can properly account for. The secondary boom and mast, neither modeled, will alter the boom current. Despite these limitations, the model at least should give a qualitative idea of boom effects. The effect on forward gain was insignificant.
APS-13 Free Space 98.000 MHz 73 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 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 -0.75 0.1250 steel 1 e5p -r -0.75 e5p r -0.75 #18 copper 1 e5p r 0 e5p r -0.75 0.1250 steel 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 1 0 1.25 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 -1.25 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 e1p 1 0 r 0 x1 y5 0 d 1 x1 y5 0 w2 y6 -s1 d 1 w2 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 w2 -y6 s1 d 1 w2 -y6 s1 x5 y6 s1 d 1 x5 y6 s1 x6 y5 0 d 1 x6 y5 0 f r 0 d shift x e2p 1 0 r 0 x1 y5 0 d 1 x1 y5 0 w2 y6 -s1 d 1 w2 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 w2 -y6 s1 d 1 w2 -y6 s1 x5 y6 s1 d 1 x5 y6 s1 x6 y5 0 d 1 x6 y5 0 f r 0 d shift x e3p 1 0 r 0 x1 y5 0 d 1 x1 y5 0 w2 y6 -s1 d 1 w2 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 w2 -y6 s1 d 1 w2 -y6 s1 x5 y6 s1 d 1 x5 y6 s1 x6 y5 0 d 1 x6 y5 0 f r 0 d shift x e4p 1 0 r 0 x1 y5 0 d 1 x1 y5 0 w2 y6 -s1 d 1 w2 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 w2 -y6 s1 d 1 w2 -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 15, 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. I modeled the feedpoint as a straight wire connecting the terminal bolts.
88–108 MHz