Antennacraft FM10

The Antennacraft FM10 is a log-Yagi array with ten elements on a 117″ boom. Three of the elements are driven.

I modeled the antenna with the AO 9.67 Antenna Optimizer program. This image shows the antenna geometry.

This shows segmentation detail for the phasing lines and feedpoint. I added a wire across the feedpoint terminals and placed a source at its center. Blue dots mark analysis segments. The red dot is the feedpoint.

Joe Roberts used this FM10 in the late 1970s at Wilbraham, Massachusetts.

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      188-j80     1.77     0.35      0.03      6.80      16.24
    89      210-j60     1.53     0.20      0.03      7.00      20.30
    90      230-j48     1.38     0.11      0.02      7.12      23.05
    91      251-j43     1.27     0.06      0.02      7.21      23.89
    92      271-j44     1.20     0.04      0.02      7.31      24.16
    93      290-j52     1.20     0.04      0.02      7.38      24.37
    94      308-j69     1.26     0.06      0.02      7.45      24.64
    95      322-j95     1.37     0.11      0.02      7.50      24.06
    96      324-j130    1.52     0.19      0.02      7.53      22.14
    97      312-j168    1.72     0.32      0.02      7.53      20.60
    98      284-j200    1.96     0.48      0.02      7.49      19.34
    99      245-j219    2.25     0.69      0.02      7.41      18.26
   100      205-j223    2.56     0.93      0.02      7.31      17.32
   101      169-j215    2.90     1.18      0.02      7.20      16.43
   102      142-j200    3.21     1.40      0.02      7.11      15.74
   103      123-j181    3.45     1.57      0.02      7.05      15.17
   104      111-j162    3.57     1.65      0.03      7.07      14.74
   105      107-j144    3.52     1.62      0.03      7.20      14.49
   106      111-j131    3.28     1.45      0.03      7.45      14.50
   107      121-j128    2.99     1.24      0.03      7.72      14.80
   108      129-j144    2.96     1.22      0.03      7.79      15.54

Antenna File

Antennacraft FM10
Free Space
98.000 MHz
50 6063-T832 wires, inches
de1 = 14.625			; driven element locations
de2 = 27
de3 = 39.375
d = .11				; phasing-line diameter
r = 3 / 2			; half of rivet spacing (insulated elements)
h = 12.375 / 2			; half of DE spacing
y1 = r * (1 - 3.375 / h)	; y at first phasing-line bend
y2 = r * (1 - 3.875 / h)	; y at second bend
y3 = -y2			; y at third bend
y4 = -y1			; y at fourth bend
x1 = de1 + 3.375		; x at first phasing-line bend, rear line
x2 = de1 + 3.875		; x at second bend
x3 = de2 - 3.875		; x at third bend
x4 = de2 - 3.375		; x at fourth bend
x5 = de2 + 3.375		; x at first phasing-line bend, forward line
x6 = de2 + 3.875		; x at second bend
x7 = de3 - 3.875		; x at third bend
x8 = de3 - 3.375		; x at fourth bend
s = .5 / 2			; half of phasing-line crossover spacing
b = .75				; feedpoint bolt length

1      0.0000  -32.8750    0.0000      0.0000   -2.0000    0.0000    0.3750
1      0.0000   -2.0000    0.0000      0.0000    2.0000    0.0000    1.28
1      0.0000    2.0000    0.0000      0.0000   32.8750    0.0000    0.3750

1     14.6250  -29.5000    0.0000     14.6250   -r         0.0000    0.3750
1     14.6250    r         0.0000     14.6250   29.5000    0.0000    0.3750

1     27.0000  -28.2500    0.0000     27.0000   -r         0.0000    0.3750
1     27.0000    r         0.0000     27.0000   28.2500    0.0000    0.3750

1     39.3750  -21.8750    0.0000     39.3750   -r         0.0000    0.3750
1     39.3750    r         0.0000     39.3750   21.8750    0.0000    0.3750

1     43.1250  -25.0000   -1.9375     43.1250   -2.0000   -1.9375    0.3750
1     43.1250   -2.0000   -1.9375     43.1250    2.0000   -1.9375    1.28
1     43.1250    2.0000   -1.9375     43.1250   25.0000   -1.9375    0.3750

1     53.7500  -24.0000    0.0000     53.7500   -2.0000    0.0000    0.3750
1     53.7500   -2.0000    0.0000     53.7500    2.0000    0.0000    1.28
1     53.7500    2.0000    0.0000     53.7500   24.0000    0.0000    0.3750

1     65.2500  -24.0000    0.0000     65.2500   -2.0000    0.0000    0.3750
1     65.2500   -2.0000    0.0000     65.2500    2.0000    0.0000    1.28
1     65.2500    2.0000    0.0000     65.2500   24.0000    0.0000    0.3750

1     83.7500  -24.0000    0.0000     83.7500   -2.0000    0.0000    0.3750
1     83.7500   -2.0000    0.0000     83.7500    2.0000    0.0000    1.28
1     83.7500    2.0000    0.0000     83.7500   24.0000    0.0000    0.3750

1    100.3750  -24.0000    0.0000    100.3750   -2.0000    0.0000    0.3750
1    100.3750   -2.0000    0.0000    100.3750    2.0000    0.0000    1.28
1    100.3750    2.0000    0.0000    100.3750   24.0000    0.0000    0.3750

1    117.3750  -24.0000    0.0000    117.3750   -2.0000    0.0000    0.3750
1    117.3750   -2.0000    0.0000    117.3750    2.0000    0.0000    1.28
1    117.3750    2.0000    0.0000    117.3750   24.0000    0.0000    0.3750
				  
4     de1        r         0          x1        y1         0         d 
1      x1       y1         0          x2        y2        -s         d 
10     x2       y2         -s         x3        y3        -s         d 
1      x3       y3         -s         x4        y4         0         d 
4      x4       y4         0         de2        -r         0         d 
4     de1       -r         0          x1        -y1        0         d 
1      x1      -y1         0          x2        -y2        s         d 
10     x2      -y2         s          x3        -y3        s         d 
1      x3      -y3         s          x4        -y4        0         d 
4      x4      -y4         0         de2         r         0         d 
4     de2        r         0          x5        y1         0         d 
1      x5       y1         0          x6        y2         s         d 
8      x6       y2         s          x7        y3         s         d 
1      x7       y3         s          x8        y4         0         d 
4      x8       y4         0         de3        -r         0         d 
4     de2       -r         0          x5        -y1        0         d 
1      x5      -y1         0          x6        -y2       -s         d 
8      x6      -y2        -s          x7        -y3       -s         d 
1      x7      -y3        -s          x8        -y4        0         d 
4      x8      -y4         0         de3         r         0         d 

1     de3       -r         0         de3        -r        -b        .125    zinc
1     de3       -r        -b         de3         r        -b         #16    copper
1     de3        r         0         de3         r        -b        .125    zinc
1 source
Wire 49, center

I modeled the 4" x 1.625" x 0.5" x 0.05" bracket as a U channel with YO 8.00 to get
the 1.28" equivalent diameter of the inner taper section for the parasitic
elements.

June 15, 201888108 MHz