Tom Russell writes:
>GOOD QUESTION!
>The radiation resistance of a Dipole Antenna changes with height above
>ground. (See ARRL Handbook or Antenna Book). It goes through a
>minimum between 5/8 and 3/4 wavelengths (82 to 105 feet on 40 meters).
>Power = I squared R - For a constant power output, current (and
>gain) is maximized when the radiation resistance is the least.
>40M dipoles between 80 and 100 ft have proven to be very effective DX
>antennas. For local communtication up to 600-800 miles, 40 to 50 ft
>works quite >well.
What's more important...radiation resistance or a low incident wave
angle? I'll take the low angle of radiation myself. Would you want a
20 meter dipole (or yagi) at 41 to 52 feet? Certainly for the lower
angles, one wavelength above ground is the minimum acceptable height.
True, radiation resistance may be less...but look at where it's going.
73, Rick, N6CR in Atlanta
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