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Constructing an HF End-Fed Half-Wave (EFHW) vertical antenna, the resource details the winding of a monoband matching unit, inspired by _AA5TB_, designed to provide a 50 Ohm impedance match without a ground plane or antenna tuner. It specifies the use of a _T200-2_ ferrite core for the transformer, outlining the 13-turn secondary and 2-turn primary winding process with enamelled copper wire. The document also describes the integration of a coax capacitor, whose length is critical for tuning and varies by band, with specific starting lengths provided for 20m, 17m, 15m, 12m, and 10m operation. The practical application section guides the builder through tuning the antenna using an antenna analyzer, emphasizing the iterative process of spacing secondary windings and trimming the coax capacitor to achieve resonance at the desired band frequency. It highlights the antenna's low angle of radiation, beneficial for DX, and claims up to 2 S-points improvement over a _G5RV_ or similar doublet when used as an omnidirectional vertical. A comprehensive shopping list, including specific part numbers from _Rapid Electronics_, is provided, along with advice on selecting fiberglass fishing poles for support and suitable antenna wire.

End-Fed Half-Wave Antennas (EFHWAs) are analyzed for their utility in portable QRP operations, emphasizing their simplicity, efficiency, and predictable radiation patterns compared to other portable antenna types. The discussion contrasts EFHWAs with vertical antennas, random length wires, and center-fed dipoles, highlighting the common pitfalls of each, such as ground system dependency for verticals and feedline issues for dipoles. The article details the electrical half-wavelength calculation using the formula L (Ft) = 468/F(MHz) and explains how EFHWAs can be resonant on harmonic frequencies, enabling multiband operation. Various deployment configurations are presented, including the inverted L, inverted Vee, sloping wire, and vertical setups, each with specific advantages for radiation angle and polarization. For instance, a vertical EFHWA offers a low angle of radiation suitable for DX contacts without requiring an extensive ground system. The resource also addresses the counterpoise requirements, suggesting a quarter-wavelength wire or connection to a metallic structure for decoupling. A schematic diagram for a simple parallel-tuned circuit tuner, based on the _Rainbow Bridge/Tuner_ design, is provided, detailing component values for 30 and 40 meters, including a 6 microhenry toroidal inductor and a 20-100 picofarad mica compression capacitor. The tuner's adjustment process for SWR matching is also outlined.

Constructing an End-Fed Half-Wave (EFHW) antenna offers a practical solution for HF operators seeking a multiband wire antenna without the need for extensive radial systems. This design typically employs a high-impedance transformer at the feed point, matching the antenna's inherent high impedance to a 50-ohm coaxial feedline. The article specifically details a 2012 approach, focusing on a transformer with a 49:1 turns ratio, which is a common configuration for EFHW antennas. The resource outlines the construction of a wire element cut for a half-wavelength on the lowest desired band, with specific coil arrangements enabling operation on harmonically related bands such as 40m, 20m, and 10m. It discusses the physical dimensions and winding details for the matching transformer, often utilizing a ferrite toroid core to achieve the necessary impedance transformation. The content provides insights into the operational principles and practical considerations for deploying such an antenna, including methods for tuning and optimizing performance across multiple amateur radio bands. While acknowledging that the presented information from 2012 may be superseded by newer insights, it serves as a foundational reference for understanding EFHW antenna theory and construction.

How to Design and Build a Field Expedient End-Fed Half-Wave Antenna for 20m, 40m and 80m. This Shorty 80m EFHW comprises a 49:1 autotransformer (to match the very high impedance at the end of a half-wave wire), a half-wavelength wire for 40m (also a quarter-wavelength for 80m), a loading coil and a short tail wire. The coil and the short tail wire (about 6 feet) make up the other quarter wave on 80m.

Building an End-Fed Half-Wave (EFHW) antenna from a kit, as detailed by Frank Bontenbal, PA2DKW, with process photos by Bob Inderbitzen, NQ1R, offers a practical approach for hams. This specific kit, a collaboration between ARRL and HF Kits, targets 10, 15, 20, and 40 meters, making it a versatile option for HF operations. Unlike a center-fed dipole, the EFHW is a half-wavelength antenna fed at one end, which simplifies deployment, particularly for portable use. The construction guide meticulously outlines the assembly of the 49:1 impedance matching network, crucial for transforming the antenna's high impedance (around 2,500 Ohms) to a transceiver-friendly 50 Ohms. Steps include preparing the enclosure by drilling holes for the coaxial connector and antenna connections, followed by the precise winding of enameled copper wire onto a toroid to create the transformer. The guide emphasizes careful insulation removal and soldering for reliable connections. Final assembly involves integrating a 100 pF capacitor for higher band compensation, soldering the transformer's primary and secondary sides, and conducting SWR tests with a 2K7 resistor or a half-wavelength wire. The document also provides examples of wire lengths for different bands, such as 16 feet for 10 meters or 66 feet for 40 meters, demonstrating the transformer's adaptability for various half-wavelength configurations.

Schemaric diagram for a 80m, 40m, 30m, 20m EFHW Antenna Antenna Tuner. The tuner has been designed for an antenna length of 41m and the counterpoise 7.5m.

This page discusses the CLEFHW (Coil Loaded End-Fed Half-Wave) antenna, a portable variation of the popular EFHW design for ham radio operators. The article explains how the CLEFHW allows for backpack portable operation without the need for trees or poles, making it ideal for POTA activations and rapid deployment scenarios. The author details the design, optimization for 20m band, and compares efficiency to full-length wire antennas. Suitable for hams interested in portable antenna solutions and quick setup options for amateur radio activities.

This page provides guidance on designing an End-Fed Half-Wave (EFHW) or Random-Length antenna for amateur HF bands, such as 80 or 40 meters. The content explains how to optimize the antenna for multi-band use and match it to a 50-ohm system using an unun. Hams can generate radiation patterns, VSWR charts, and antenna current diagrams for their customized antenna designs. Understanding how antenna dimensions affect performance is essential for successful field operations. The page caters to ham radio operators looking to build efficient and effective HF antennas for their stations.

The Portable EFHW antenna for the 40, 20, 15, and 10-meter bands utilizes a broadband transformer with a 1:49 ratio, designed on a PCB by either Jan or DL2MAN. The design incorporates an **FT114 core**, offering an alternative to the FT82 core. The antenna requires precisely 20.5 meters of DX Wire Ultralight for optimal performance. Additional components include DX Wires "Dyneema" 1mm rope and 1mm bricklayers string for structural support. The SWR plot indicates performance at two elevation heights: 5.5 meters (blue line) and 4 meters (yellow line), demonstrating optimization for low-elevation portable use without poles. The antenna's components, including spool and rope tensioners, are available for 3D printing, with spool dimensions scaled to 130% for a length of approximately 110mm. The design emphasizes simplicity and portability, suitable for field deployment.