portable-antennas - EFHW antenna designer

Should I use an EFHW (end-fed half-wave) or an EFRL (end-fed random-length) wire?

It's a matter of personal taste whether you use, or design, an EFHW (end-fed half-wave) or an EFRL (end-fed random-length) 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.
EFRL - 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 such lengths, to get you started:

Length, feet	Length, meters	Bands^*
29.0	8.84	30m - 10m
35.5	10.82	40m - 10m
41.0	12.50	40m - 10m
52.0	15.85	60m - 10m
58.0	17.68	60m - 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
347.0	105.77	160m - 10m
407.0	124.05	160m - 10m
423.0	128.93	160m - 10m
^* Some bands may not be available or tunable in your setup

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!

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. ½ λ:

m Calculated length: m

Antenna type

Set type:

calculated ½-wave resonant end-fed wire
random-length non-resonant end-fed wire

Antenna configuration

Configure as:

two-section inverted-L or inverted-vee
single section sloper

Antenna wire

Wire core:

mm diameter

Material:

Insulation:

thickness

Ins. type:

Corr. factor:

Min. weight:

grams

Antenna height

Foot height:

Support ht.:

m (Calculated)

First antenna section

Length:

m Set to:

Angle:

Vertical Angle from vertical: °

Second antenna section

Length:

Angle:

Horizontal Angle from horizontal: °

Counterpoise

Length:

λ = m Info

Direction:

Inductance load

Value:

µH

Position:

m above F-P

Dimensions:

Wire dia.:	mm	Mean rad.:	mm
Turns:		Width:	mm

Antenna overview

Foot
height

Support
height

Counter-
poise

Section #1

Section #2

Length

Angle

Length

Angle

EFHW (End-Fed Half-Wave) 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: ⬥ Inductance load: ●

Show display hints:

Effect of coax- and system-losses on VSWR

When a coaxial cable is used to connect the antenna to a transmitter, the cable introduces signal loss, the magnitude of which can vary strongly with both frequency and antenna feed-point impedance.

The main blue VSWR curve for this antenna is calculated at the antenna feed-point. The optional green curve represents the VSWR "seen" at the transmitter after losses in the coaxial cable are taken into account.

At frequencies of antenna resonance, the blue and green curves usually coincide closely, since the coax contributes little additional attenuation at those frequencies. At frequencies away from resonance, however — often those corresponding to WARC bands — the feed-point impedance may become highly mismatched, producing very high VSWR values in the blue curve while the green curve shows substantially lower values.

This reduction in VSWR at the transmitter occurs because signal losses in the coaxial cable attenuate both the forward and reflected waves. As a result, the reflected signal returning to the transmitter is weaker, causing the transmitter-end VSWR to appear lower than the actual feed-point VSWR.

This effect can make some bands appear more "usable" from the transmitter's perspective, even though the antenna system may still be operating inefficiently at those frequencies.

The green curve represents the "flattening" of the VSWR caused by the coax. Additional losses elsewhere in the system can further reduce the transmitter-end VSWR - these may include:

ferrite heating and winding losses in baluns/ununs
common-mode currents suppression
coupling of RF energy into nearby ground and objects
matching network / antenna tuner losses

The magnitude of such losses, and their effect on actual radiated RF power, can only be estimated reliably through careful analysis of a particular antenna setup. In every-day portable operations, such losses can only be roughly estimated; however, comparisons can be made between commercially-produced EFHW and OCFD antennas for amateur radio use, and carefully-configured NEC models of those same antennas. Useful estimates can then be made of the efficiency of the commercial products by comparing their published VSWR curves, and the VSWR curves produced from the models.

The dashed red curve (VSWR-FIELD) represents what might be measured in the field by an antenna analyzer connected to the transmitter end of the coax when this antenna is erected "in the field," i.e. either when operating portable, or at the home QTH. This curve approximates the effect on VSWR of all the sources of signal loss mentioned above, and illustrates how real-world losses can further flatten the measured VSWR, either with a home-brew, or a commercial, EFHW antenna.

Improved transmitter-end VSWR therefore does not necessarily imply improved radiation efficiency: in some cases, a significant proportion of the transmitted power may simply be lost: dissipated as heat within the antenna system. Read more...

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 %

EFHW antenna designer - correction factors reference

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

End-effect multiplication factor - dependent on wire diameter and frequency

End effect multiplication factor

Wavelength / wire diameter ratio, λ/d:

End-effect multiplication factor :

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

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

Title	Band	Freq. kHz	Foot Height	Section #1		Section #2		Cp./Rad. Length
Title	Band	Freq. kHz	Foot Height	Length	Angle	Length	Angle	Cp./Rad. Length
Some title	40m	7000	1	1	1	1	1	1

Coordinates can be used to model the same antenna in a separate program

#	Freq. MHz	Section Length	Angle	Element coordinates
#	Freq. MHz	Section Length	Angle	x1	y1	x2	y2
1	1	1	1	1	1	1	1

Copy this CSV text and paste into your favorite spreadsheet program

EFHW antenna designer

By changing the band, and/or changing the fundamental frequency (use the arrow buttons),
display of the harmonics of that frequency will be updated in real time.

Calculate inductance load coil dimensions

Inductance load coil

It is common practice to insert a small fixed series inductance into the first section of an EFHW antenna to help with tuning of bands above the antenna's principal band: this may be configured to be switchable. Without such an inductance load, VSWR minima on the higher bands could occur too far above those bands' limits to be of any practical use.

Calculate coil dimensions

We'll use the inductance value L_µH which you have chosen from the dropdown, to estimate the dimensions of an inductance load coil to shift VSWR minima to better align with band limits for bands above the principal design band. Show more...

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 diameter, and the greater the diameter of the coil itself, the lower the coil losses will be.

Choose ground type of land in the vicinity of the antenna:	Conductivity: S/m Dielectric const.: F/m
View radiation patterns:	Azimuth Elevation Polarization patterns
	3D pattern Choose type: Classic 3D plot NEW 360° heatmap plot
Set ref. elevation angle:	Auto Choose:
Set ref. azimuth angle:	Auto 0° (inline) 90° (broadside)
Radiation patterns for:	Principal band only Choose band:
	Patterns hover info: Show as tooltip Show radial line and/or texts
Impedance transformer:	unun
View VSWR chart:	VSWR Check on: Principal band Bands range From: To:
Effect of coax on VSWR: Coax losses info » » »	Include coax losses Coax length: Type: Effect of coax- and system-losses on VSWR When a coaxial cable is used to connect the antenna to a transmitter, the cable introduces signal loss, the magnitude of which can vary strongly with both frequency and antenna feed-point impedance. The main blue VSWR curve for this antenna is calculated at the antenna feed-point. The optional green curve represents the VSWR "seen" at the transmitter after losses in the coaxial cable are taken into account. At frequencies of antenna resonance, the blue and green curves usually coincide closely, since the coax contributes little additional attenuation at those frequencies. At frequencies away from resonance, however — often those corresponding to WARC bands — the feed-point impedance may become highly mismatched, producing very high VSWR values in the blue curve while the green curve shows substantially lower values. This reduction in VSWR at the transmitter occurs because signal losses in the coaxial cable attenuate both the forward and reflected waves. As a result, the reflected signal returning to the transmitter is weaker, causing the transmitter-end VSWR to appear lower than the actual feed-point VSWR. This effect can make some bands appear more "usable" from the transmitter's perspective, even though the antenna system may still be operating inefficiently at those frequencies. The green curve represents the "flattening" of the VSWR caused by the coax. Additional losses elsewhere in the system can further reduce the transmitter-end VSWR - these may include: ferrite heating and winding losses in baluns/ununs common-mode currents suppression coupling of RF energy into nearby ground and objects matching network / antenna tuner losses The magnitude of such losses, and their effect on actual radiated RF power, can only be estimated reliably through careful analysis of a particular antenna setup. In every-day portable operations, such losses can only be roughly estimated; however, comparisons can be made between commercially-produced EFHW and OCFD antennas for amateur radio use, and carefully-configured NEC models of those same antennas. Useful estimates can then be made of the efficiency of the commercial products by comparing their published VSWR curves, and the VSWR curves produced from the models. The dashed red curve (VSWR-FIELD) represents what might be measured in the field by an antenna analyzer connected to the transmitter end of the coax when this antenna is erected "in the field," i.e. either when operating portable, or at the home QTH. This curve approximates the effect on VSWR of all the sources of signal loss mentioned above, and illustrates how real-world losses can further flatten the measured VSWR, either with a home-brew, or a commercial, EFHW antenna. Improved transmitter-end VSWR therefore does not necessarily imply improved radiation efficiency: in some cases, a significant proportion of the transmitted power may simply be lost: dissipated as heat within the antenna system. Read more...
View currents diagram:	Antenna currents diagram
View Smith chart:	Smith chart
Antenna gains at 0° elevation:
Feed-point impedance:
Estimated bandwidth:

portable-antennas.com Home page	ANTENNAS Linked dipole OCFD EFHW Vertical Delta loop Half-square Moxon	SPECIALS "Hentenna" "VP2E" antenna "4DX" Dipoles-beam "LoG" RX antenna	EXTRAS Coax data + charts Calculators Reference	MORE Support - antennas Support - patterns Support - general About us Contact
Web Hosting by Digital Ocean

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.

EFHW antenna designer

Antenna performance

Effect of coax- and system-losses on VSWR

End effect multiplication factor

Inductance load coil

Calculate coil dimensions