The FM 2500HD is a high-band VHF-TV antenna once sold for FM use. The boom length is 70″ (electrical length 68″). The red dot marks the 300Ω feedpoint.
I modeled the antenna with the AO 9.67 Antenna Optimizer. 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 32.3-j18.1 9.33 4.56 0.02 -4.89 -0.28
89 33.4-j13.7 9.01 4.44 0.02 -4.78 -0.34
90 34.5-j9.4 8.70 4.32 0.02 -4.69 -0.40
91 35.6-j4.9 8.42 4.21 0.02 -4.60 -0.48
92 36.9-j0.6 8.14 4.09 0.02 -4.53 -0.56
93 38.0+j3.6 7.89 3.99 0.02 -4.47 -0.66
94 39.2+j7.7 7.67 3.89 0.02 -4.43 -0.79
95 40.3+j11.7 7.46 3.80 0.02 -4.41 -0.94
96 41.3+j15.6 7.28 3.72 0.02 -4.43 -1.14
97 42.3+j19.5 7.13 3.65 0.02 -4.48 -1.38
98 43.0+j23.3 7.01 3.60 0.02 -4.61 -1.71
99 43.6+j26.9 6.94 3.56 0.02 -4.85 -2.19
100 43.4+j30.4 6.98 3.58 0.02 -5.30 -2.91
101 41.7+j34.4 7.29 3.72 0.02 -6.28 -4.20
102 37.5+j38.9 8.15 4.09 0.04 -8.39 -6.70
103 23.9+j59.3 13.06 5.78 0.14 -7.63 -5.46
104 44.6+j96.1 7.44 3.79 0.11 0.99 14.97
105 73.0+j83.9 4.45 2.22 0.03 1.11 10.65
106 75.9+j75.3 4.22 2.08 0.02 0.36 6.25
107 75.9+j73.8 4.21 2.07 0.01 -0.15 4.50
108 76.7+j74.8 4.17 2.05 0.01 -0.42 3.61
Denny's FM 2500HD Free Space Symmetric 98 MHz 12 6063-T832 wires, inches r = 30.5 ; element half-lengths de1 = 28 de2 = 23.5 d1 = 12.75 d2 = 12 d3 = 12 d4 = 17 d5 = 12 d6 = 11.75 dep1 = 10.5 ; element positions dep2 = 19.75 d1p = 24 d2p = 28 d3p = 34.5 d4p = 39.75 d5p = 51.75 d6p = 68 p = 1.375 ; phasing line half-spacing 1 0 .68 0 0 r 0 .375 1 dep1 0 -1 dep1 p -1 #18 ; feedpoint jumper 1 dep1 p -1 dep1 p 0 .1875 ; feedpoint bolts 1 dep1 p 0 dep2 p 0 .231 ; 0.375" x .05" strap 1 dep1 p 0 dep1 de1 0 .375 1 dep2 p 0 dep2 de2 0 .375 1 d1p 0 -1.5 d1p d1 -1.5 .375 1 d2p 0 -1.5 d2p d2 -1.5 .375 1 d3p 0 -1.5 d3p d3 -1.5 .375 1 d4p .68 0 d4p d4 0 .375 1 d5p 0 0 d5p d5 0 .375 1 d6p 0 0 d6p d6 0 .375 1 source Wire 2, end1
See the enthusiastic customer testimonials here, here, and here.
88–108 MHz