Finco FM-5

The Finco FM-5 is a dual-driven Yagi with ten elements on a 117″ boom. It was once manufactured by the Finney Company.

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

This shows the segmentation of the driven elements and phasing line. Blue dots mark analysis segments. The red dot is the feedpoint.

Mike Bugaj used this FM-5 in the early 1970s at Anaheim, California. An instruction sheet is here.

Modeling Results

Calculated performance is for 28 analysis segments per conductor 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.

Frequency  Impedance    SWR   Mismatch  Conductor   Forward     F/R 
   MHz        ohms             Loss dB   Loss dB   Gain dBd      dB 
    88     188 + j60    1.70     0.30      0.02      7.14      21.58
    89     183 + j84    1.83     0.39      0.02      7.11      20.27
    90     183 + j104   1.93     0.46      0.01      7.13      19.10
    91     187 + j121   1.99     0.50      0.01      7.19      18.19
    92     195 + j135   2.00     0.51      0.01      7.29      17.43
    93     207 + j144   1.96     0.48      0.01      7.43      16.84
    94     225 + j147   1.87     0.42      0.02      7.62      16.37
    95     246 + j140   1.73     0.32      0.02      7.84      16.04
    96     263 + j118   1.55     0.21      0.02      8.08      15.80
    97     269 + j83    1.37     0.11      0.02      8.30      15.77
    98     248 + j38    1.27     0.06      0.02      8.46      15.98
    99     212 + j15    1.43     0.14      0.02      8.48      16.18
   100     171 + j13    1.76     0.34      0.02      8.36      16.47
   101     138 + j26    2.20     0.66      0.02      8.10      16.72
   102     115 + j47    2.70     1.03      0.02      7.77      16.86
   103     102 + j72    3.13     1.34      0.03      7.45      16.78
   104     101 + j96    3.32     1.48      0.03      7.27      16.50
   105     114 + j118   3.10     1.32      0.03      7.33      16.08
   106     146 + j119   2.46     0.85      0.03      7.62      15.91
   107     160 + j73    2.02     0.52      0.04      7.65      16.21
   108     105 + j40    2.92     1.19      0.05      6.52      17.44

Antenna File

Finco FM-5
Free Space
98 MHz
61 6063-T832 wires, inches
rp = 0
de1p = 16
de2p = 33
d1p = 45
d2p = 57
d3p = 69
d4p = 81
d5p = 93
d6p = 105
d7p = 117
r = 35
de1 = 30
de2 = 23
d1 = 25.5
d2 = 25.5
d3 = 25.5
d4 = 24.5
d5 = 24.5
d6 = 23.5
d7 = 23.5
de1s = 10
de2s = 12
d = .375		; Tubing diameter
eqd = 1.35		; Equivalent diameter of 0.5" sheath at bracket
b = 2.3125		; Bracket half-length
w = .11			; Phasing line diameter
x1 = 27.5
xm = 29.5
x2 = 31.5
f = 21

1    rp   -r    0    rp   -b    0    d  ; Reflector
1    rp   -b    0    rp    b    0  eqd
1    rp    b    0    rp    r    0    d

1   de1p -de1  -2   de1p -de1s -2  .375 ; Driven element 1
1   de1p -de1s -2   de1p -1    -2  .375
1   de1p  1    -2   de1p  de1s -2  .375
1   de1p  de1s -2   de1p  de1  -2  .375
1   de1p -de1   0   de1p -de1s  0  .375
1   de1p -de1s  0   de1p   -b   0  .375
1   de1p   -b   0   de1p    b   0   eqd
1   de1p    b   0   de1p  de1s  0  .375
1   de1p  de1s  0   de1p  de1   0  .375
1   de1p -de1  -2   de1p -de1   0  .375
1   de1p  de1  -2   de1p  de1   0  .375
1   de1p -de1s -2   de1p -de1s  0  .375
1   de1p  de1s -2   de1p  de1s  0  .375

1   de2p -de2  -2   de2p -de2s -2  .375 ; Driven element 2
1   de2p -de2s -2   de2p -1    -2  .375
1   de2p  1    -2   de2p  de2s -2  .375
1   de2p  de2s -2   de2p  de2  -2  .375
1   de2p -de2   0   de2p -de2s  0  .375
1   de2p -de2s  0   de2p   -b   0  .375
1   de2p   -b   0   de2p    b   0   eqd
1   de2p    b   0   de2p  de2s  0  .375
1   de2p  de2s  0   de2p  de2   0  .375
1   de2p -de2  -2   de2p -de2   0  .375
1   de2p  de2  -2   de2p  de2   0  .375
1   de2p -de2s -2   de2p -de2s  0  .375
1   de2p  de2s -2   de2p  de2s  0  .375

1   d1p   -d1   0   d1p    -b   0    d  ; Directors
1   d1p    -b   0   d1p     b   0  eqd
1   d1p     b   0   d1p    d1   0    d
1   d2p   -d2   0   d2p    -b   0    d
1   d2p    -b   0   d2p     b   0  eqd
1   d2p     b   0   d2p    d2   0    d
1   d3p   -d3   0   d3p    -b   0    d
1   d3p    -b   0   d3p     b   0  eqd
1   d3p     b   0   d3p    d3   0    d
1   d4p   -d4   0   d4p    -b   0    d
1   d4p    -b   0   d4p     b   0  eqd
1   d4p     b   0   d4p    d4   0    d
1   d5p   -d5   0   d5p    -b   0    d
1   d5p    -b   0   d5p     b   0  eqd
1   d5p     b   0   d5p    d5   0    d
1   d6p   -d6   0   d6p    -b   0    d
1   d6p    -b   0   d6p     b   0  eqd
1   d6p     b   0   d6p    d6   0    d
1   d7p   -d7   0   d7p    -b   0    d
1   d7p    -b   0   d7p     b   0  eqd
1   d7p     b   0   d7p    d7   0    d

1   de1p -1 -2     f    -1 -2      w	; Transmission line
1   f    -1 -2     x1   -1 -2      w
1   x1   -1 -2     xm 0 -1.125     w
1   xm 0 -1.125    x2    1 -2      w
1   x2    1 -2     de2p  1 -2      w
1   de1p  1 -2     f     1 -2      w
1   f     1 -2     x1    1 -2      w
1   x1    1 -2     xm 0 -2.875     w
1   xm 0 -2.875    x2   -1 -2      w
1   x2   -1 -2     de2p -1 -2      w
2   f     1 -2     f    -1 -2      w

1 source
Wire 61, center

This models the Finco FM-5 receiving antenna for the FM broadcast band. The
elements use a 0.5"-diameter reinforcing sheath that I included in the mounting
bracket model. It extends about 1.5" past the bracket, which I ignored.

June 15, 201888108 MHz