Gain
Gain describes the concentration of radiated energy in selected directions. It is generally expressed in dBi or dBd.
F1SYH technical guide
Amateur radio antenna encyclopedia
Operating principles, history, performance, radiation patterns, construction plans and tuning advice.
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Understanding antennas
An antenna converts radio-frequency current into electromagnetic waves during transmission. During reception, it performs the reverse operation. Its operation depends on geometry, electrical length, feed system, surroundings and ground.
Impedance
Feed-point impedance must be matched to the feed line and transmitter, usually designed for 50 Ω.
SWR
Standing wave ratio indicates the quality of the match between antenna, feed line and transmitter.
Polarization
Polarization may be horizontal, vertical, circular or elliptical depending on element orientation.
Radiation pattern
The radiation pattern represents the distribution of energy in space and identifies lobes and nulls.
Ground influence
Height, ground conductivity and nearby obstacles strongly affect take-off angle and real performance.
Antenna families
Each family offers a different compromise between gain, directivity, size, efficiency, cost and construction difficulty.
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antennas displayed
Half-wave dipole
The reference balanced antenna, simple to build and highly efficient when installed sufficiently high.
EFHW
End-fed half-wave antenna, often multiband, matched to coax through an impedance transformer.
Vertical antennas
Quarter-wave, half-wave or 5/8 λ. Omnidirectional and effective for DX when the ground system is efficient.
Loops and Delta loops
Full-wave loops, often quieter on receive and usable with several polarizations.
Yagi-Uda
Directional antenna using a driven element, a reflector and one or more parasitic directors.
Quad, Moxon and Hexbeam
Compact directional antennas providing a good compromise between gain, size and multiband performance.
Magnetic loop
Compact high-Q antenna, highly selective and demanding in terms of capacitor design and safety.
J-Pole, Slim Jim and collinear
Popular VHF and UHF vertical antennas for local operation, repeaters and portable installations.
Delta Loop
The Delta Loop is a triangular full-wave loop. It may provide horizontal or vertical polarization depending on the feed-point position.
Magnetic loop
A magnetic loop is a compact antenna tuned by a variable capacitor. Its small size is achieved at the cost of narrow bandwidth and very high circulating current.
J-Pole antenna
The J-Pole is a vertical half-wave radiator fed through a parallel quarter-wave matching section.
Slim Jim antenna
The Slim Jim is a folded vertical antenna derived from the J-Pole. It is especially popular for portable VHF and UHF use.
Moxon rectangle
The Moxon is a compact two-element directional antenna with folded ends. It provides good front-to-back performance in less space than a conventional two-element Yagi.
G5RV antenna
The G5RV is a multiband antenna consisting of a doublet and a balanced-line section used as an impedance transformer.
ZS6BKW antenna
The ZS6BKW is a multiband doublet with a balanced-line section optimized to present more favorable impedances on several amateur bands.
Windom and OCF dipole
An OCF dipole is fed away from its centre to obtain usable impedance on several bands. Modern versions generally use a transformer and coaxial cable.
Hexbeam
The Hexbeam is a compact directional wire antenna using folded elements supported by six spreaders.
Cubical Quad
The Cubical Quad uses one or more full-wave loops, usually square or diamond shaped, to form a directional antenna.
Discone antenna
The Discone combines an upper disc and lower cone. It is especially valued for wideband VHF/UHF reception.
Log-periodic antenna
A log-periodic antenna is a wideband directional array whose element lengths and spacing follow a geometric progression.
Folded dipole
A folded dipole uses two parallel conductors connected at both ends. It presents higher impedance than a simple dipole.
Multiband doublet
A multiband doublet is a dipole that is not necessarily resonant, fed with low-loss balanced line and an antenna tuner.
Double Zepp
The Double Zepp is a long wire antenna generally made of two legs near five eighths wavelength each.
Long Wire
A Long Wire is a conductor generally longer than one wavelength at the operating frequency.
Random Wire
A Random Wire is an end-fed wire whose length is selected to avoid difficult impedances on the intended bands.
Inverted-V dipole
An Inverted-V is a dipole with a high centre and both legs sloping toward the ground.
Sloper antenna
A Sloper is a dipole or resonant wire installed at an angle between a high and low support.
T2FD
The T2FD is a tilted folded dipole terminated with a non-inductive resistor. It favours bandwidth over maximum efficiency.
5/8-wave vertical
A 5/8-wave vertical uses a radiator longer than a quarter-wave to flatten the vertical pattern and increase low-angle radiation.
Collinear antenna
A collinear stacks several vertical radiating sections fed in phase to concentrate energy toward the horizon.
Coaxial collinear
A coaxial collinear uses alternating coaxial sections to create several phased radiating elements.
Sleeve Dipole
A Sleeve Dipole is a vertical dipole whose lower half is formed by a conductive sleeve surrounding the coaxial feed line.
Beverage antenna
The Beverage is a very long, low receiving antenna designed for directivity and signal-to-noise ratio rather than absolute signal strength.
K9AY loop
The K9AY is a compact resistively loaded receiving loop, usually switchable between several directions.
Pennant antenna
The Pennant is a small resistively terminated triangular loop designed for directional reception.
Flag antenna
The Flag is a resistively terminated rectangular receiving loop designed to provide a strong null in one direction.
EWE antenna
The EWE is a receiving antenna made of two vertical sections joined by a horizontal wire and terminated toward ground.
Turnstile antenna
The Turnstile combines two perpendicular dipoles fed 90 degrees out of phase.
Eggbeater antenna
The Eggbeater uses two perpendicular vertical loops fed in quadrature for satellite reception and transmission.
Lindenblad antenna
The Lindenblad uses four tilted dipoles around a vertical axis to produce circular polarization and broad coverage.
Cross-Yagi
A Cross-Yagi combines two identical Yagi antennas mounted at right angles on the same boom.
Helical antenna
An axial-mode helix is a directional circularly polarized antenna widely used for UHF, satellites and microwave work.
Patch antenna
A patch antenna is a flat metallic element above a ground plane and separated by a dielectric substrate.
BiQuad antenna
The BiQuad uses two square loops formed from one conductor and positioned in front of a reflector.
Cobra antenna
The Cobra is a multiband wire antenna whose two legs are made from three-conductor line connected in a specific configuration.
W3DZZ antenna
The W3DZZ is a multiband dipole using two resonant trap circuits installed symmetrically in the legs.
Carolina Windom
The Carolina Windom is an off-centre-fed dipole variant that intentionally uses part of the feed line as a vertical radiator.
G5RV Junior
The G5RV Junior applies the G5RV principle at approximately half the full-size length.
Extended Double Zepp
The Extended Double Zepp, or EDZ, is an approximately 1.25-wavelength wire antenna providing bidirectional gain.
Half-Square
The Half-Square consists of two quarter-wave vertical elements joined by a half-wave horizontal section.
Bobtail Curtain
The Bobtail Curtain uses three quarter-wave vertical elements joined by two half-wave horizontal sections.
Lazy H
The Lazy H combines two parallel horizontal dipoles mounted one above the other and connected by a phasing line.
Sterba Curtain
The Sterba Curtain is a large wire array made of rectangular phased cells designed for high gain.
Rhombic antenna
The Rhombic is a very large diamond-shaped antenna, normally resistively terminated for long-distance HF communication.
V-Beam antenna
A V-Beam consists of two long wires forming an open V toward the desired radiation direction.
Hentenna
The Hentenna is a rectangular open or folded antenna mainly used on VHF and UHF.
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General comparison
These figures are indicative. Actual performance depends on height, ground, losses, frequency and construction quality.
| Antenna | Typical gain | Directivity | Bandwidth | Required space | Difficulty | Recommended use |
|---|---|---|---|---|---|---|
| Dipôle demi-onde | 2,15 dBi | Low | Medium | Medium | Easy | HF local et DX |
| EFHW | ≈ 2 dBi | Low | Narrow | High | Moderate | Portable et multibande |
| Verticale 1/4 λ | ≈ 2 dBi | Low | Wide | Low | Moderate | DX et omnidirectionnel |
| Delta Loop | 2 à 4 dBi | Medium | Medium | High | Moderate | HF et réception silencieuse |
| Yagi 3 éléments | 6 à 8 dBi | High | Medium | Medium | Advanced | DX et réduction des brouillages |
| Hexbeam | 5 à 7 dBi | High | Medium | Medium | Advanced | DX multibande |
| Boucle magnétique | -5 à 0 dBi | Medium | Narrow | Low | Advanced | Espaces réduits |
| J-Pole | 2 à 3 dBi | Low | Medium | Low | Easy | VHF/UHF local et portable |
Dimension calculator
The calculation provides a starting length. The antenna must then be measured in its final position using a NanoVNA or antenna analyzer.
Half-wave dipole — total length
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Dipole — length of each leg
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Quarter wavelength
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Theoretical half wavelength
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Full wavelength
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EFHW — starting length
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Antenna history
Amateur radio antennas result from more than a century of scientific, military, industrial and amateur experimentation.
1886–1888
Heinrich Hertz demonstrates radio waves
Hertz’s experiments confirmed James Clerk Maxwell’s theoretical work. His dipoles and resonators were direct ancestors of modern antennas.
1926
Birth of the Yagi-Uda antenna
Shintaro Uda developed the parasitic-element antenna. Hidetsugu Yagi later contributed to its international recognition.
1929
The Windom antenna
Loren G. Windom, W8GZ, popularized an off-center-fed antenna that inspired many modern multiband variants.
1946
Louis Varney introduces the G5RV
Louis Varney, G5RV, designed a multiband antenna using a balanced-line section as an impedance transformer.
1946–1947
Development of the Cubical Quad
Clarence C. Moore, W9LZX, developed the Quad to solve high-voltage problems in tropical broadcast antennas.
Construction and installation
A correctly calculated antenna may perform poorly if construction or installation is inadequate.
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Essential safety
An antenna, mast or guy wire must never be able to touch a power line, even if it falls. Disconnect and ground the installation during thunderstorms.
Encyclopedia development
This page is the portal to the future F1SYH antenna knowledge base. Each antenna will progressively receive a complete article with plans, measurements, simulations and practical feedback.