The Triax FM 8S is an eight-element Yagi for the FM broadcast band made in Europe. It has two reflectors and a 2.3-meter (91″) boom.
I modeled the antenna with the AO-Pro 8.50 Antenna Optimizer program. The red dot marks the feedpoint. I did not model the mounting brackets.
Below are calculated performance figures for a segmentation density of 30 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/R is the ratio of forward power to that of the worst backlobe in the rear half-plane. The SWR reference impedance is 300Ω.
88.000 MHz: Impedance 93.8 + j25.4 ohms
SWR 3.22
Mismatch Loss 1.41 dB
Wire Loss 0.02 dB
Mismatched Gain 5.32 dBd
F/R 9.75 dB
93.000 MHz: Impedance 272 + j119 ohms
SWR 1.53
Mismatch Loss 0.19 dB
Wire Loss 0.01 dB
Mismatched Gain 6.86 dBd
F/R 19.29 dB
98.000 MHz: Impedance 383 + j50 ohms
SWR 1.33
Mismatch Loss 0.09 dB
Wire Loss 0.01 dB
Mismatched Gain 7.45 dBd
F/R 23.80 dB
103.000 MHz: Impedance 398 - j155 ohms
SWR 1.69
Mismatch Loss 0.30 dB
Wire Loss 0.02 dB
Mismatched Gain 7.96 dBd
F/R 17.13 dB
108.000 MHz: Impedance 54.6 - j4.5 ohms
SWR 5.49
Mismatch Loss 2.83 dB
Wire Loss 0.11 dB
Mismatched Gain 5.17 dBd
F/R 12.87 dB
Triax FM-8S Free Space Symmetric 98 MHz 18 6063-T832 wires, meters 1 0 -0.835 0.34 0 0.835 0.34 .01 1 0 -0.835 -.34 0 0.835 -.34 .01 1 0.38 -.7225 -.03 0.38 .7225 -.03 .01 1 0.38 .27 .03 0.38 .7225 .03 .01 1 0.38 -.7425 -.01 0.38 -.7425 .01 .01 1 0.38 .7425 -.01 0.38 .7425 .01 .01 1 0.38 -.7425 -.01 0.38 -.7225 -.03 .01 1 0.38 -.7425 .01 0.38 -.7225 .03 .01 1 0.38 .7425 -.01 0.38 .7225 -.03 .01 1 0.38 .7425 .01 0.38 .7225 .03 .01 1 0.38 -.7225 .03 0.38 -.27 .03 .01 1 0.38 -.27 .03 0.38 0 -.015 .01 1 0.38 .27 .03 0.38 0 -.015 .01 1 0.45 -0.6575 0 0.45 0.6575 0 .01 1 0.90 -0.6425 0 0.90 0.6425 0 .01 1 1.315 -.618 0 1.315 .618 0 .01 1 1.77 -.618 0 1.77 .618 0 .01 1 2.305 -.596 0 2.305 .596 0 .01 1 source Wire 3, center Disable bent-wire correction
88–108 MHz