EFHW antenna designer

Design an End-Fed Half-Wave (EFHW) or an End-Fed Random-Length (EFRL) antenna, in inverted-L, or inverted-Vee, or sloper 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 several higher bands, and can therefore be a good multi-band antenna. Being an end-fed antenna with a high feed-point impedance and high feed-point voltage, it is most often matched to a 50-ohm system using an unun, typically 49:1, 64:1, etc.  Read more...

EFHW or end-fed random wire?  » » »

Should I use an EFHW (end-fed half-wave) or an end-fed random wire?
It's a matter of personal taste whether you use, or design, an EFHW (end-fed half-wave) or an end-fed random wire.  You are both the designer and the end-user, so you make the choice.
What's the difference between the two?
The two types differ in (1) how the length of the wire used is set, and (2) which bands are covered:
  • EFHW - as the name suggests, this is a half-wave antenna (half-wave on the principal band) and so its' length is calculated for you by the program using basic physics.  This calculation, being based on the principal frequency/band, means that this type is resonant on at least one frequency/band, and can also be resonant on multiple other, harmonically-related frequencies/bands as well.  The WARC bands are not generally well covered.  The EFHW will present very high impedances, typically around few thousand ohms, and will be used with a high-ratio unun in the range 49:1, 64:1 or even higher.
  • end-fed random wire - this is an antenna, the length of which is carefully chosen to be not resonant on any of the frequencies or bands where it will be used. In addition, the length chosen should result in an antenna which presents impedances which are in the middle to high hundreds of ohms on bands of interest, and an unun ratio in the range of 8:1 to 10:1 would be used to transform the antenna's impedance down to the 50 ohms of the coaxial cable.   Many bands can be covered, including some WARC bands.
If you eventually do decide to use the random-length wire option, then a few optimal lengths, or length-ranges, have been worked out by several operators, and we list here a few of those lengths, to get you started:
Length,
feet		 Length,
meters		  Bands*
29.0 8.84  40m - 10m
35.5 10.82  40m - 10m
41.0 12.50  40m - 10m
52.0 15.85  40m - 10m
58.0 17.68  40m - 10m
71.0 21.64  80m - 10m
107.0 32.61  80m - 10m
119.0 36.27  80m - 10m
135.0 41.15  160m - 10m
148.0 45.11  160m - 10m
203.0 61.87  160m - 10m
*Some bands may not be available or tunable.
This list is intended as a helpful guide only (you can find other such lists online).  Some of these lengths may not work for you, or may not tune on all the bands you need: you can use our End-fed random wire antenna lengths calculator to help you decide which length you will use.
Once you have erected your antenna, you will need to cut/adjust it to length while checking its' performance on those bands of interest to you, using your TRX and tuner. The end-fed random-length wire antenna is at best a compromise antenna, but which can nonetheless give good results!

Get started  » » »

  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    Info
Nom. ½ λ: m     Calculated length:   m
Antenna configuration
Configure as:
  
Antenna wire
Wire core: mm  diameter
Material:    Info
Insulation: thickness   
Ins. type:   Corr. factor:
Min. weight: grams
Antenna height
Foot height: m 
Support ht.: m (Calculated)
First antenna section
Length: m    Set to:
Angle: Angle from vertical: °
Second antenna section
Length: m
Angle: Angle from horizontal: °
Counterpoise (radial)
Length: λ     = m    Info
Direction:
Inductance load
Value: µH    Info
Position: m above feed-point
Antenna overview
Foot
height 		Support
height 		Counter-
poise 		Section #1 Section #2
Length Angle Length Angle
 
 
 EFHW (End-Fed Half-Wave) 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: ⬥    Inductance load: ●
 

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:     Info
  Set azimuth angle for elevation plot:     Info

Info
Radiation patterns for: Info
 
       
       
View VSWR chart: Check on:   From:   To:   
Display impedance curves: Using unun   
Impedance curves scales:   
Effect of coax on VSWR: Coax length: Type:   Info
View currents diagram:
View Smith chart:    Info
Antenna gains
at 0° elevation:
Antenna impedance:
Frequency range: