[Antennas] 30 Meter Ground plane

[Terry Conboy]

At 07:36 AM 2004-02-25, W3HKK@aol.com wrote:
>Tilting the radials at 45 degrees will raise your feedpoint to about 52 ohms
>but it also raises your angle of radiation making it somehwat less effective
>for dx but better for  1000-2500 mile distances.

I did a quick model with EZNEC and drooping the radials barely changes the 
angle of radiation.

With the antenna base at 15 feet height, the peak of the vertical pattern 
is at 19 degrees with 0.48 dBi gain when using 4 horizontal radials.

If the radials are drooped at -30 degrees, the vertical lobe peaks at 21 
degrees with 0.33 dBi gain.  At 19 degrees, the gain is 0.29 dBi.  (With 
Randy WX5L's mounting height, it isn't possible to droop at 45 degrees).

The feed impedance rises to 53 ohms with the -30 degree drooping radials.

I'd say drooping the radials is a good approach for adjusting the feedpoint 
impedance that won't have much impact on range.  Conceptually, if you droop 
radials so that they are straight down, you essentially have a vertical 
dipole, which is what WWV uses very effectively on its HF transmitters.

73, N6RY


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