Finco FM-5
The Finco FM-5 is an outdoor directional receiving antenna for the FM broadcast band once manufactured by the Finney Company. It is a dual-driven Yagi design with ten elements on a ten-foot boom.
I modeled the antenna with the AO-Pro 7.03 Antenna Optimizer program. This image shows the antenna geometry.
This shows the segmentation of the driven elements and phasing line. Blue dots indicate analysis-segment boundaries. The red dot indicates the feedpoint.
A Finco instruction sheet is here.
Modeling Results
Below 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 222 + j103 ohms
SWR 1.64
Mismatch Loss 0.26 dB
Wire Loss 0.01 dB
Mismatched Gain 7.03 dBd
F/B 22.92 dB
90.000 MHz: Impedance 234 + j138 ohms
SWR 1.77
Mismatch Loss 0.35 dB
Wire Loss 0.01 dB
Mismatched Gain 7.11 dBd
F/B 20.58 dB
92.000 MHz: Impedance 261 + j157 ohms
SWR 1.77
Mismatch Loss 0.35 dB
Wire Loss 0.01 dB
Mismatched Gain 7.32 dBd
F/B 18.80 dB
94.000 MHz: Impedance 304 + j150 ohms
SWR 1.63
Mismatch Loss 0.26 dB
Wire Loss 0.01 dB
Mismatched Gain 7.66 dBd
F/B 17.55 dB
96.000 MHz: Impedance 339 + j91 ohms
SWR 1.36
Mismatch Loss 0.10 dB
Wire Loss 0.01 dB
Mismatched Gain 8.07 dBd
F/B 16.72 dB
98.000 MHz: Impedance 303 + j5 ohms
SWR 1.02
Mismatch Loss 0.00 dB
Wire Loss 0.02 dB
Mismatched Gain 8.42 dBd
F/B 16.24 dB
100.000 MHz: Impedance 211 - j18 ohms
SWR 1.43
Mismatch Loss 0.14 dB
Wire Loss 0.02 dB
Mismatched Gain 8.47 dBd
F/B 16.00 dB
102.000 MHz: Impedance 147 + j22 ohms
SWR 2.06
Mismatch Loss 0.56 dB
Wire Loss 0.02 dB
Mismatched Gain 8.17 dBd
F/B 15.87 dB
104.000 MHz: Impedance 131 + j78 ohms
SWR 2.48
Mismatch Loss 0.87 dB
Wire Loss 0.02 dB
Mismatched Gain 7.86 dBd
F/B 15.79 dB
106.000 MHz: Impedance 178 + j103 ohms
SWR 1.97
Mismatch Loss 0.49 dB
Wire Loss 0.03 dB
Mismatched Gain 8.05 dBd
F/B 16.22 dB
108.000 MHz: Impedance 138 + j3 ohms
SWR 2.17
Mismatch Loss 0.64 dB
Wire Loss 0.05 dB
Mismatched Gain 7.24 dBd
F/B 18.70 dB
Patterns
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 = 23.75 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. Disable bent-wire correction.
More is here.
Updated July 8, 2007
