Antennacraft FM13
The Antennacraft FM13 is an outdoor receiving antenna for the FM broadcast band. It is a Log-Yagi array with 13 elements on a 140" boom. Five of the elements are driven.
I modeled the antenna with the AO-Pro 8.00 Antenna Optimizer program. This image shows the antenna geometry.
This shows segmentation detail for the phasing lines and feedpoint. Blue dots indicate analysis-segment boundaries. The red dot indicates the feedpoint.
Modeling Results
Here are calculated performance figures for a segmentation density of 40 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.
88.000 MHz: Impedance 279 + j56 ohms
SWR 1.23
Mismatch Loss 0.05 dB
Wire Loss 0.08 dB
Mismatched Gain 8.22 dBd
F/B 19.94 dB
90.000 MHz: Impedance 261 + j31 ohms
SWR 1.20
Mismatch Loss 0.03 dB
Wire Loss 0.07 dB
Mismatched Gain 8.53 dBd
F/B 19.47 dB
92.000 MHz: Impedance 232 - j1 ohms
SWR 1.29
Mismatch Loss 0.07 dB
Wire Loss 0.06 dB
Mismatched Gain 8.68 dBd
F/B 20.66 dB
94.000 MHz: Impedance 195 + j12 ohms
SWR 1.55
Mismatch Loss 0.20 dB
Wire Loss 0.05 dB
Mismatched Gain 8.67 dBd
F/B 23.46 dB
96.000 MHz: Impedance 202 + j49 ohms
SWR 1.56
Mismatch Loss 0.21 dB
Wire Loss 0.05 dB
Mismatched Gain 8.75 dBd
F/B 26.27 dB
98.000 MHz: Impedance 268 + j54 ohms
SWR 1.25
Mismatch Loss 0.05 dB
Wire Loss 0.04 dB
Mismatched Gain 9.00 dBd
F/B 23.76 dB
100.000 MHz: Impedance 308 - j63 ohms
SWR 1.23
Mismatch Loss 0.05 dB
Wire Loss 0.04 dB
Mismatched Gain 9.10 dBd
F/B 19.51 dB
102.000 MHz: Impedance 189 - j130 ohms
SWR 2.02
Mismatch Loss 0.53 dB
Wire Loss 0.04 dB
Mismatched Gain 8.67 dBd
F/B 16.32 dB
104.000 MHz: Impedance 110 - j79 ohms
SWR 2.94
Mismatch Loss 1.20 dB
Wire Loss 0.04 dB
Mismatched Gain 7.94 dBd
F/B 14.17 dB
106.000 MHz: Impedance 97.8 - j12.4 ohms
SWR 3.07
Mismatch Loss 1.30 dB
Wire Loss 0.04 dB
Mismatched Gain 7.67 dBd
F/B 13.00 dB
108.000 MHz: Impedance 171 + j39 ohms
SWR 1.79
Mismatch Loss 0.37 dB
Wire Loss 0.04 dB
Mismatched Gain 8.36 dBd
F/B 13.01 dB
Patterns
Antenna File
Antennacraft FM13
Free Space
98.000 MHz
78 6063-T832 wires, inches
de1 = 15.75 ; driven element locations
de2 = 25.75
de3 = 35.75
de4 = 45.75
de5 = 55.75
d = .11 ; phasing-line diameter
r = 3 / 2 ; half of rivet spacing (insulated elements)
h = 10 / 2 ; half of DE spacing
y1 = r * (1 - 2.375 / h) ; y at first phasing-line kink
y2 = r * (1 - 2.875 / h) ; y at second kink
y3 = -y2 ; y at third kink
y4 = -y1 ; y at fourth kink
x1 = de1 + 2.375 ; x at first phasing-line kink, rear line
x2 = de1 + 2.875 ; x at second kink
x3 = de2 - 2.875 ; x at third kink
x4 = de2 - 2.375 ; x at fourth kink
x5 = de2 + 2.375 ; x at first phasing-line kink, second line
x6 = de2 + 2.875 ; x at second kink
x7 = de3 - 2.875 ; x at third kink
x8 = de3 - 2.375 ; x at fourth kink
x9 = de3 + 2.375 ; x at first phasing-line kink, third line
x10 = de3 + 2.875 ; x at second kink
x11 = de4 - 2.875 ; x at third kink
x12 = de4 - 2.375 ; x at fourth kink
x13 = de4 + 2.375 ; x at first phasing-line kink, forward line
x14 = de4 + 2.875 ; x at second kink
x15 = de5 - 2.875 ; x at third kink
x16 = de5 - 2.375 ; x at fourth kink
s = .375 / 2 ; half of phasing-line crossover spacing
shift x -68
1 0.0000 -34.0000 0.0000 0.0000 -2.0000 0.0000 0.3750
1 0.0000 -2.0000 0.0000 0.0000 2.0000 0.0000 1.1
1 0.0000 2.0000 0.0000 0.0000 34.0000 0.0000 0.3750
1 15.7500 -30.3750 0.0000 15.7500 -r 0.0000 0.3750
1 15.7500 r 0.0000 15.7500 30.3750 0.0000 0.3750
1 25.7500 -28.5000 0.0000 25.7500 -r 0.0000 0.3750
1 25.7500 r 0.0000 25.7500 28.5000 0.0000 0.3750
1 35.7500 -26.4375 0.0000 35.7500 -r 0.0000 0.3750
1 35.7500 r 0.0000 35.7500 26.4375 0.0000 0.3750
1 45.7500 -25.4375 0.0000 45.7500 -r 0.0000 0.3750
1 45.7500 r 0.0000 45.7500 25.4375 0.0000 0.3750
1 55.7500 -21.8750 0.0000 55.7500 -r 0.0000 0.3750
1 55.7500 r 0.0000 55.7500 21.8750 0.0000 0.3750
1 63.7500 -24.0625 0.0000 63.7500 -2.0000 0.0000 0.3750
1 63.7500 -2.0000 0.0000 63.7500 2.0000 0.0000 1.1
1 63.7500 2.0000 0.0000 63.7500 24.0625 0.0000 0.3750
1 77.3750 -24.0625 0.0000 77.3750 -2.0000 0.0000 0.3750
1 77.3750 -2.0000 0.0000 77.3750 2.0000 0.0000 1.1
1 77.3750 2.0000 0.0000 77.3750 24.0625 0.0000 0.3750
1 89.3750 -24.0625 0.0000 89.3750 -2.0000 0.0000 0.3750
1 89.3750 -2.0000 0.0000 89.3750 2.0000 0.0000 1.1
1 89.3750 2.0000 0.0000 89.3750 24.0625 0.0000 0.3750
1 101.3750 -24.0625 0.0000 101.3750 -2.0000 0.0000 0.3750
1 101.3750 -2.0000 0.0000 101.3750 2.0000 0.0000 1.1
1 101.3750 2.0000 0.0000 101.3750 24.0625 0.0000 0.3750
1 113.3750 -24.0625 0.0000 113.3750 -2.0000 0.0000 0.3750
1 113.3750 -2.0000 0.0000 113.3750 2.0000 0.0000 1.1
1 113.3750 2.0000 0.0000 113.3750 24.0625 0.0000 0.3750
1 125.3750 -24.0625 0.0000 125.3750 -2.0000 0.0000 0.3750
1 125.3750 -2.0000 0.0000 125.3750 2.0000 0.0000 1.1
1 125.3750 2.0000 0.0000 125.3750 24.0625 0.0000 0.3750
1 137.3750 -24.0625 0.0000 137.3750 -2.0000 0.0000 0.3750
1 137.3750 -2.0000 0.0000 137.3750 2.0000 0.0000 1.1
1 137.3750 2.0000 0.0000 137.3750 24.0625 0.0000 0.3750
1 de1 r 0 x1 y1 0 d aluminum
1 x1 y1 0 x2 y2 -s d aluminum
1 x2 y2 -s x3 y3 -s d aluminum
1 x3 y3 -s x4 y4 0 d aluminum
1 x4 y4 0 de2 -r 0 d aluminum
1 de1 -r 0 x1 -y1 0 d aluminum
1 x1 -y1 0 x2 -y2 s d aluminum
1 x2 -y2 s x3 -y3 s d aluminum
1 x3 -y3 s x4 -y4 0 d aluminum
1 x4 -y4 0 de2 r 0 d aluminum
1 de2 r 0 x5 y1 0 d aluminum
1 x5 y1 0 x6 y2 -s d aluminum
1 x6 y2 -s x7 y3 -s d aluminum
1 x7 y3 -s x8 y4 0 d aluminum
1 x8 y4 0 de3 -r 0 d aluminum
1 de2 -r 0 x5 -y1 0 d aluminum
1 x5 -y1 0 x6 -y2 s d aluminum
1 x6 -y2 s x7 -y3 s d aluminum
1 x7 -y3 s x8 -y4 0 d aluminum
1 x8 -y4 0 de3 r 0 d aluminum
1 de3 r 0 x9 y1 0 d aluminum
1 x9 y1 0 x10 y2 -s d aluminum
1 x10 y2 -s x11 y3 -s d aluminum
1 x11 y3 -s x12 y4 0 d aluminum
1 x12 y4 0 de4 -r 0 d aluminum
1 de3 -r 0 x9 -y1 0 d aluminum
1 x9 -y1 0 x10 -y2 s d aluminum
1 x10 -y2 s x11 -y3 s d aluminum
1 x11 -y3 s x12 -y4 0 d aluminum
1 x12 -y4 0 de4 r 0 d aluminum
1 de4 r 0 x13 y1 0 d aluminum
1 x13 y1 0 x14 y2 -s d aluminum
1 x14 y2 -s x15 y3 -s d aluminum
1 x15 y3 -s x16 y4 0 d aluminum
1 x16 y4 0 de5 -r 0 d aluminum
1 de4 -r 0 x13 -y1 0 d aluminum
1 x13 -y1 0 x14 -y2 s d aluminum
1 x14 -y2 s x15 -y3 s d aluminum
1 x15 -y3 s x16 -y4 0 d aluminum
1 x16 -y4 0 de5 r 0 d aluminum
1 de5 -r 0.0000 de5 -r -0.7500 .125 steel
1 de5 r 0.0000 de5 r -0.7500 .125 steel
1 de5 -r -0.7500 de5 0 -3.2500 #22 copper
1 de5 r -0.7500 de5 0 -3.2500 #22 copper
1 source
Wire 78, end2
Bracket 4" x 1.625" x 1/32", modeled as a U channel by YO to get the 1.1"
equivalent diameter of the inner taper section for the parasitic elements.
The 0.75" wires near the feedpoint model the terminal bolts.
The #22 wires model split 300-ohm twinlead (long-lead Radio Shack balun).
More is here.
Updated July 8, 2007
