portable-antennas - Vertical 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

Wvl-fraction :

Antenna configuration

Configure as:

Standard length Shortened length Info

Antenna wire

Wire core:

mm diameter

Material:

Insulation:

thickness

Ins. type:

Corr. factor:

Main vertical section

Length:

Base height:

Radials - for 1/4-wave and 5/8-wave vertical antenna variants

No. of radials:

Radials length:

λ = m Info

Radials angle:

° from horizontal Info

Counterpoise - for 1/2-wave vertical antenna variant

Length:

λ = m Info

Antenna overview

Main vertical section

Radials / Counterpoise

Length

Top
height

Base
height

No.

Length

Angle

End
height

Vertical 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 ...

portable-antennas.com

Antenna feed-point: ⬥ Load coil: ●

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. Read more...

Note also that, for vertical antennas, the NEC engine used to generate the data for the elevation radiation pattern over-estimates the radiated gain at angles below the pseudo-Brewster angle specific to the antenna, ground type and frequency: this is due to unmodelled ground absorption effects. Below this angle, the gains are less, and often much less, than are presented in the elevation pattern.

Export antenna dimensions to file

Export format:
Antenna diagram:	Use original view Use current view
PDF options: Toggle all	Include radiation patterns Include VSWR chart Include currents diagram Include Smith chart If you include any of these options, make sure you refresh the required radiation patterns, charts and diagrams for your antenna before exporting.
Collecting data:	0 %

Vertical antenna designer - correction factors reference

Length-correction factor used in this application - this will be applied automatically

Radials angle impedances - how feed-point impedance varies with radials angle
End-effect multiplication factor - dependent on wire diameter and frequency
Half-wave vertical impedances - 1/2-wave vertical impedances by counterpoise length

Radials angle impedances

Both the 1/4-wave ground-plane (GP), and the 5/8-wave, vertical antennas will need a system of radials attached at the feed-point.

How many radials are to be used is left to the builder to establish - sometimes a single radial will suffice to "get a signal out", although a minimum of 3 or 4 will give excellent results.

Sloping the radials downward from the feed-point will alter the feed-point impedance - how much will depend on the angle, as can be readily determined from the accompanying chart.

In general, the 5/8-wave vertical has a higher feed-point impedance than the 1/4-wave vertical for a given number of radials and radials angle.

Data for the chart derived empirically for 1/4-wave and 5/8-wave vertical antennas using the NEC v4.2 engine. Chart for illustrative purposes only - actual values for a particular antenna will depend on its' configuration.

End effect multiplication factor

Wavelength / wire diameter ratio, λ/d:

End-effect multiplication factor :

Half-wave vertical impedances

The 1/2-wave vertical antenna, unlike its' 1/4-wave and 5/8-wave cousins, presents a high impedance at the feed-point, typically around 1300 Ω to 2000 Ω.

The reactive part of this impedance is often high also: a counterpoise is attached at the feed-point to minimize this reactive component.

Many antenna builders agree that the optimum counterpoise length, to bring the reactive component close to zero, is 1/20λ (0.05λ) - the accompanying chart shows this very clearly.

Calculate loading coil dimensions for shortened vertical

Calculate loading coil dimensions for a shortened vertical

Building a 1/4-wave vertical antenna for the low HF bands can be problematic, since the full length required can be difficult or impossible for many to manage, especially when operating portable. This calculator uses the principle of inductive base loading to electrically lengthen a much-shortened radiator.

Part #1 - Calculate coil inductance

We first calculate the inductance required to shorten our vertical antenna, given the frequency, antenna wire length, position of the coil and the antenna wire diameter. Show more...

To do this, we use the classic formula, originally published by J. Hall, "Off-center loaded dipole antennas", QST Sept 1974, pp28-34, and re-printed in the ARRL Antenna Handbook, 20th edition, p6-31:

\[ L_{\mu H} = \frac{10^6}{68 \pi^2 f^2} \left\{ \frac{ [\ln(\frac{24(234/f - B)}{D}) - 1] × [(1 - fB/234)^2 - 1] }{(234/f - B)} - \frac{ [\ln(\frac{24(A/2 - B)}{D}) - 1] × [((fA/2 - fB)/234)^2 - 1] }{(A/2 - B)} \right\} \]

where

L_µH = calculated coil inductance in micro-Henrys,
f = frequency in MHz,
A = total vertical length,
B = vertical length from the feedpoint to the center of the loading coil,
D = diameter of the antenna wire.

The formula as it stands required lengths to be in feet and inches, but this calculator allows you to enter metric or feet/inches length units, as you wish:

Frequency:	MHz (auto)	Coil inductance: µH
New antenna length:	meters
Coil center-height:	meters
Antenna wire diameter:	mm

Part #2 - Calculate coil dimensions

We'll now use the inductance L_µH, which we have derived using the above calculator, to estimate the parameters of a coil which we can use to electrically lengthen a short vertical antenna for use in the lower HF bands. Show more...

Coil former: The relative permeabilities μ_r of most plastics commonly used as coil formers are very close to unity (as for air), with the notable exception of PVC, which should not be used. Hence, in electromagnetic terms they mostly behave identically to air for inductance calculations, and can be safely be ignored in the calculations of coil inductance.

Single-layer helical coil The formula used here is for a single-layer air-cored helical coil:
\[ L_{\mu H} = \frac{N^2 R^2}{9R + 10W} \] where L_µH = coil inductance in micro-Henrys, N = number of turns of wire, R = coil mean radius in inches, W = coil width in inches.	Fig.1 - Single-layer coil
This formula is claimed to be accurate to within 1 percent for coils having W > 0.8R.

Coil inductance:

µH

No. of turns:
Coil width:	mm
Coil wire len.:	m
RF resistance:	Ω

Coil mean radius:

Coil wire diameter:

Windings spacing:

Est. coil Q-factor:

If you intend to use enamelled wire in your coil (acceptable for the higher HF bands or VHF), you can take a coil wire diameter value from this dropdown list of standard enamelled wire sizes:

Enamelled wire sizes:
(Some wire sizes may not be readily available from your suppliers)

For the lower HF bands, you should use as large a wire diameter as is consistent with planned coil size and portability. The greater the coil wire (or tube) diameter, and the greater the coil diameter, the lower the coil losses will be. Be aware that, at these low frequencies, a shortened antenna will also incur greater ground return losses, and greater proximity losses. "There's no such thing as a free lunch" - shortened antennas with loading coils are inherently lossy, and less efficient - sometimes much less so - than antennas of standard length.

Part #3 - A note on radials lengths for shortened verticals

Once you have decided on the length of your shortened radiator section, you need to consider the lengths of the radials you will be using with your antenna. Basically speaking, since radials act more like a loss-reduction system than tuned elements, any length of radials is better than no radials at all, and so shortened radials can be used with your coil-loaded short vertical antenna, but there will be a trade-off:

shorter radials = easier to handle,
but reduced antenna efficiency.

Shortening the vertical with a loading coil mainly fixes reactance (resonance), but it does not reduce the current that must flow in the "ground system". Radials form the return path, or image plane, for current returning to your feed system, so shortening the radials will both:

increase signal loss, and
decrease the bandwidth of your antenna,

Keep this in mind when choosing a length for your radials: 0.25 λ is the optimum choice in terms of efficiency, but if space is at a premium, you may decide to use more radials, each perhaps a little shorter than the 0.25 λ optimum length. There is no special radial-lengths rule to be applied here: ultimately, you make a choice, build your antenna, and test it.

An expanded version of this coil calculator, with more details and references, can be found here

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	Wire diam.	Antenna length	Base height	No. of radials	Radials angle
a	b	c	e	d	f	g	h

Antenna sections
Section		Segment start			Segment end
Segment	Length	x	y	z	x	y	z
Vertical	1	1	1	1	1	1	1

Copy this CSV text and paste into your favorite spreadsheet program

Vertical antenna designer

Choose ground type of land in the vicinity of the antenna:	Conductivity: S/m Dielectric const.: F/m
View radiation patterns:	Azimuth Elevation 3D pattern Polarization patterns
Set ref. elevation angle:	Auto Choose:
Set ref. azimuth angle:	Auto 0° (inline) 90° (broadside)
	Patterns hover info: Show as tooltip Show radial line and/or texts
View VSWR chart:	VSWR
Display impedance curves:	Using unun
Impedance curves scales:	Shared Independent:
View currents diagram:	Antenna currents diagram
View Smith chart:	Smith chart
Antenna gains at 0° elevation:
Antenna efficiency:
Antenna impedance:
Frequency range:

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