portable-antennas - Half-square antenna designer

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.
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.
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 scroll down in the page 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: Show person-height plane

Principal band
Band:
Frequency:	kHz
Nom. length:	m Corrected length: m
Antenna configuration
Configure antenna as:	current-fed full-wave single bander voltage-fed EFHW, multi-bander
Antenna wire
Wire core:	mm diameter
Insulation:	thickness
Ins. type:	Corr. factor:
Antenna supports
Height:	m (At support point)
Antenna foot height
Foot height:	m
Vertical sections length
Length:	m
Top section length (ref.)
Length:	m
Counterpoise (radial) - not applicable to current-fed single-bander
Length:	λ = m
Inductance load - not applicable to current-fed single-bander
Value:	µH
Position:	m above foot

Antenna overview

Antenna sections lengths

Foot
height

Full
height

Est.
imped.

Counterp.
/ radial

Half-square antenna designer

Use the controls on the left-hand side to configure your antenna.
When you are happy with your configuration, press the "Show antenna" button to display your antenna in interactive 3D graphics mode in this area.
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: ●

Show display hints:

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.

Export antenna dimensions to file

Export format:
CSV options:	Text delimiter:
CSV options:	Column separator:

EFHW antenna designer - correction factors reference

Various factors used in this application

End-effect multiplication factor - dependent on wire diameter and frequency
Feed-point impedance dependency on counterpoise length (EFHW variant only)

End effect multiplication factor

Wavelength / wire diameter ratio, λ/d:

End-effect multiplication factor :

Half-square EFHW impedance by counterpoise length

The half-square antenna, configured as a voltage-fed EFHW antenna, has - like all end-fed antennas - a very high impedance, typically between 2500 and 5000 Ω or more.

This high impedance has also a large reactive component, which can be moderated by the use of a counterpoise at the feed-point. By choosing an appropriate counterpoise length, the impedance can be brought close to zero, resulting in a neary purely resistive feed-point impedance.

The optimum counterpoise length has been found, by trial and error, to be about 1/20 (=0.05) lambda - the accompanying chart, displaying values calculated for a 40-meter half-square EFHW, shows this very clearly.

If you choose to insert an inductance load in series in your antenna - to optimize the VSWR minima at higher bands - the feed-point impedance will be even higher than those in the chart. It's up to the user to configure the antenna as they desire, and to choose an appropriate unun ratio for that configuration.

Save antenna configuration

Give your antenna configuration a meaningful title...

Title:

Manage saved antenna configurations

Your saved antenna configurations:

Click on
an antenna
configuration
to select it

Double-click
to load a
configuration

Coordinates of each section can be used to model this antenna in a separate program

Main antenna characteristics
Band	Frequency (kHz)	Units	Support height	Wire diam.	Antenna config.	Induct. load
Band	Frequency (kHz)	Units	Support height	Wire diam.	Antenna config.	Value	Pos.
a	b	c	d	e	Current-fed	N/A	N/A

Antenna sections
Section		Segment start			Segment end
Ident.	Length	x	y	z	x	y	z
Driver #1	1	1	1	1	1	1	1

Copy this CSV text and paste into your favorite spreadsheet program

You may choose an example from the list and import it into your "Favourites" list

Title	Band	Freq. kHz	Units	Wire Dia.	Supp. Ht.	Section #1		Section #2		Cp./Rad. Length
Title	Band	Freq. kHz	Units	Wire Dia.	Supp. Ht.	Length	Angle	Length	Angle	Cp./Rad. Length
Some title	40m	7000	m	1	1	1	1	1	1	1

Half-square antenna designer

Choose ground type of land in the vicinity of the antenna:	Conductivity: S/m Dielectric const.: F/m
View radiation patterns:	Azimuth Set elevation angle for azimuth plot: Auto Choose: Elevation Set azimuth angle for elevation plot: Auto Choose: 3D Polarization patterns
Check prop. patterns on:	Principal band Choose band:
View VSWR chart:	VSWR Check on: Principal band Bands range From: To:
Display impedance curves:	Using unun
Impedance curves scales:	Shared Independent:
Effect of coax on VSWR:	Include coax losses Coax length: Type:
View currents diagram:	Antenna currents diagram
View Smith chart:	Smith chart
Antenna gains at 0° elevation:
Antenna impedance:
Frequency range: