Forward Gain vs Antenna Height

Click graph to change ground type

Permittivity Conductivity
     81        5000 mS/m   Salt water
     80           1        Fresh water
     20          30        Pastoral, low hills, rich soil
     13           5        Pastoral, medium hills and forestation, heavy clay soil
     10           2        Sandy, dry, flat, coastal
      5           1        Cities, industrial areas
      3           0.55     Desert

These graphs show forward gain for horizontal, vertical, and tilted orientation of a halfwave dipole for center heights between 3 and 50 feet. These are NEC-2 results using Sommerfeld-Norton ground for a 98 MHz circularly polarized signal arriving at a 1° elevation angle. The gain reference is a circularly polarized isotropic antenna in free space. The difference between the solid and dotted green curves is F/B for the tilted dipole.

Apply the curves to any antenna by adding its free-space gain in dBd to the Y axis. The model is for flat ground with a single specular reflection and no obstructions. Only general trends hold for irregular terrain where scattering at multiple points causes complex wave interference.


November 9, 202388–108 MHz