OCFD antenna designer

Design an Off-Center-Fed Dipole (OCFD) antenna, in either flat-top or inverted-Vee form, using a single main support. This type of antenna is designed for one principal amateur HF band, usually 80 meters or 40 meters, but typically displays VSWR minima on at least two higher bands, and can therefore be a good multi-band antenna. The impedance at the feed-point of this antenna is often stated to be in the range of 200 ohms to 250 ohms, so it is most often matched using a 4:1 unun.  Read more...

Set antenna color:    

Principal band
Frequency: kHz    ?
½ λ: m
Antenna wire
Wire core: mm  diameter
Support pole
Height: m  (At support point)
First antenna section
Length: % of total   = m
Angle: Angle from horizontal: °
Second antenna section
Length: % of total   = m
Angle: Angle from horizontal: °
Antenna overview
Section #1 Section #2 Est.
Pct. Length Angle Pct. Length Angle
Press the "Show antenna" button to display your antenna
configuration here in interactive 3D graphics mode
Antenna feed-point:

Antenna performance

Here you can generate plots of radiation patterns, VSWR chart, antenna currents diagram and Smith chart for your antenna over a choice of ground types. By changing the physical dimensions of the antenna, and refreshing these plots, you can learn a lot about how such antennas will perform in the field.
Please note that radiation patterns are here modelled over flat ground - when the antenna is erected on a hill-top or mountain summit, the surrounding sloping ground will generally cause angles in the elevation radiation pattern to be lowered in the direction of the slope: the steeper the slope, the lower the effective elevation take-off angle will be, and the better the chances of making long-distance contacts.

Choose ground type of
land in the vicinity
of the antenna:
   Conductivity: S/m    Dielectric const.: F/m
View radiation patterns:    Set elevation angle for azimuth plot:  °    ?
Set azimuth angle for elevation plot:  °    ?
Radiation patterns for: ?

View VSWR chart: Check on:   From:To:
Display impedance curves:   
Impedance curves scales:   
Effect of coax on VSWR: Coax length: Type: ?
  Show coax losses as: 
View currents diagram:
View Smith chart:
Antenna gains
at 0° elevation:
Antenna impedance:
Frequency range: