Denny's Antenna Service FM 2500HD

The FM 2500HD is a VHF-TV antenna sold for FM use. The boom length is 70″ (electrical length 68″). The red dot marks the 300Ω feedpoint.

Modeling Results

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

Antenna File

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

Reviews

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December 11, 201888108 MHz