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...

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  1. Use the controls on the left-hand side to configure your antenna - set the design frequency, antenna element lengths and angles, wire diameter, wire insulation if required, support height, etc.
  2. When you are happy with your configuration, press the "Show antenna" button to display your antenna in interactive 3D graphics mode in the area on the right-hand side. Each time you change your configuration, you should press the "Show antenna" button to register the changes to the app.
  3. After you have configured your antenna, you can then use the controls further down in the page to generate charts and diagrams to evaluate the antenna's performance - you will need to to access these controls.
    You can choose to view any combination of the available charts and diagrams: these include four radiation pattern types: azimuth, elevation, 3D and polarization patterns; other options include VSWR charts, an antenna currents diagram, and a Smith chart.

Set antenna color:    

Principal band
Band:
Frequency: kHz    ?
Nom. ½ λ: m     Corrected length:   m
Antenna wire
Wire core: mm  diameter
Insulation: thickness    ?
Ins. type:   Corr. factor:
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
Support
height 		Section #1 Section #2 Est.
imped.
Pct. Length Angle Pct. Length Angle
 
 OCFD (Off-Center-Fed Dipole) antenna designer
  1. Use the controls on the left-hand side to configure your antenna.
  2. When you are happy with your configuration, press the "Show antenna" button to display your antenna in interactive 3D graphics mode in this area.
  3. After you have configured your antenna, you can then use the controls further down in the page to generate charts and diagrams to evaluate the antenna's performance ...
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:   ?
View currents diagram:
View Smith chart:
Antenna gains
at 0° elevation:
Antenna impedance:
Frequency range: