Finco FM-5

The Finco FM-5 is a dual-driven Yagi with ten elements on a 120″ boom. It was once manufactured by the Finney Company.

I modeled the antenna with the AO 9.53 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     181 + j55    1.74     0.33      0.01      6.98     22.18
    89     181 + j75    1.82     0.38      0.01      7.00     20.98
    90     183 + j90    1.86     0.41      0.01      7.06     19.88
    91     188 + j103   1.88     0.43      0.01      7.14     18.96
    92     196 + j113   1.87     0.42      0.01      7.27     18.22
    93     207 + j118   1.81     0.38      0.01      7.43     17.65
    94     221 + j116   1.72     0.31      0.01      7.62     17.22
    95     236 + j106   1.59     0.23      0.01      7.84     16.92
    96     244 + j84    1.45     0.15      0.02      8.06     16.72
    97     241 + j55    1.35     0.10      0.02      8.24     16.69
    98     216 + j22    1.40     0.12      0.02      8.35     16.91
    99     184 + j8     1.64     0.26      0.02      8.32     17.08
   100     149 + j9     2.02     0.52      0.02      8.16     17.28
   101     120 + j23    2.52     0.89      0.02      7.87     17.40
   102    99.8 + j42.5  3.07     1.30      0.02      7.52     17.34
   103    88.4 + j64.9  3.57     1.65      0.02      7.19     17.01
   104    85.7 + j87.5  3.82     1.82      0.03      6.99     16.45
   105    93.8 + j107   3.65     1.70      0.03      7.03     15.81
   106     122 + j117   2.88     1.16      0.03      7.44     15.42
   107     141 + j86    2.35     0.77      0.04      7.59     15.53
   108     102 + j51    3.05     1.29      0.05      6.68     16.51

Antenna File

Finco FM-5
Free Space
98 MHz
45 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 = 34.25		; Actual length, 35
de1 = 30
de2 = 23
d1 = 24.75		; Actual length, 25.5
d2 = 24.75		; Actual length, 25.5
d3 = 24.75		; Actual length, 25.5
d4 = 23.75		; Actual length, 24.5
d5 = 23.75		; Actual length, 24.5
d6 = 22.75		; Actual length, 23.5
d7 = 22.75		; Actual length, 23.5
de1s = 10
de2s = 12
d = .43			; Actual diameter, .375
w = .125
x1 = 27.5
xm = 29.5
x2 = 31.5
f = 21

shift x -58		; For better geometry display

1   rp -r 0         rp r 0         d

1   de1p -de1 -2    de1p -de1s -2  .375
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 -2.3125 0 .375
1   de1p -2.3125 0  de1p 2.3125 0   1.1	; Equivalent to 0.5" tubing + bracket
1   de1p 2.3125 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
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 -2.3125 0 .375
1   de2p -2.3125 0  de2p 2.3125 0   1.1
1   de2p 2.3125 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 d1 0         d
1   d2p -d2 0     d2p d2 0         d
1   d3p -d3 0     d3p d3 0         d
1   d4p -d4 0     d4p d4 0         d
1   d5p -d5 0     d5p d5 0         d
1   d6p -d6 0     d6p d6 0         d
1   d7p -d7 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
1   f     1 -2     f    -1 -2      w

1 source
Wire 45, center

This models the Finco FM-5 receiving antenna for the FM broadcast band. Each
parasitic element half-length was shortened by 0.75" to account for the inner
0.5"-diameter reinforcement tubing section, the rectangular element-mounting
bracket, and the 1"-square boom. The bracket and reinforcement sections
increase element effective diameter to 0.43". The driven elements are modeled
using actual lengths and diameters, plus an inner 1.1"-diameter section
equivalent to the reinforcement section and mounting bracket. All corrections
and equivalents were computed with the YO Yagi Optimizer program.

August 27, 201388108 MHz