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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 While acknowledging that the presented information from 2012 may be superseded by newer insights, it serves as a foundational reference for understanding EFHW antenna theory and construction.

Schematic diagram of a two tone audio oscillator by VK3YE

Modem Telephone Super Filters For HF and AM Radio Interference.

A website for college and university amateur radio clubs to showcase themselves, work together, and promote amateur radio. Alumni and interested people can learn more about what college and university amateur radio clubs are doing.

A resource page for Kendoowd TS-850 HF transceiver

How to setup and configure the buddipole antenna in the J-Pole mode for the six meter band

Why build antennas out of copper and not aluminum or stainless steel. Selecting the best metals for antennas evaluating the conductivity factor.

Sponsored by the Scandinavian Amateur Radio Teleprinter Group

Over 100 distinct RF connector types are available from AIR802, including popular UHF series PL-259 plugs and SO-239 sockets, designed for a wide array of coaxial cable dimensions. The company specializes in producing connectors compatible with common amateur radio cables like RG-8, RG-213, and RG-58, ensuring reliable signal integrity for antenna systems and shack interconnections. Their product line extends to various coaxial cable types and pre-made antenna cable assemblies, offering ready-to-deploy solutions for hams. AIR802 also provides custom cable assemblies and pigtails, catering to specific installation requirements for transceivers, tuners, and amplifiers. These pre-fabricated options simplify station setup, reducing the need for field termination of connectors. Michael Bryant is the contact for inquiries regarding their range of RF components, which are essential for building robust and efficient amateur radio stations.

Delta Electronics Manufacturing, a global manufacturer, specializes in _RF connectors_, adapters, and cable assemblies, providing custom interconnect solutions with superior performance. Their Advanced Vertically Integrated (AVI) global facilities emphasize efficiency, quality, flexibility, and cost control across their product lines. The company serves diverse industries, including broadcast and audio, test and measurement, military, aerospace, and public safety communications. For instance, Delta supplies RF interfaces for military aircraft, satellite launch vehicles, and missiles, maintaining a long-standing QPL supplier status. Their field-tested RF interconnects are also crucial for two-way radios, base station equipment, and antenna systems in public safety applications, ensuring reliable performance in critical communication infrastructure. Delta's solutions extend to commercial aircraft and semiconductor manufacturing, where their RF interconnects power etch equipment, deposition equipment, and chip testing systems worldwide.

A 70 cm yagi antenna design by YU7EF includes tables with antenna elements dimension and spacing. This UHF Yagi antenna plan provides a maximum gain of 17.93 db

This page introduces the world IARU Grid Locator system, and discusses how to find out what your own Grid Locator is.

SVARA - Saginaw Valley Amateur Radio Association

Some technical information for on Opto Isolation, Transformer Isolation, Surge Protection

This is the blog for the M0BGR Amateur Radio Station. I am based in London, England but frequently go out mobile or portable.

A blog from poland about VHF and Satellite operations, including D-Star. Many pictures and movies from this active vhf dxer

The OCFD Off-Center-Fed Dipole Antenna is an excellent multiband antenna that is relatively simple to construct, yet gets quite decent performance.

A website dedicated to microwave operations and technical projects by AD6IW

Shortwave listening web site from Brazil

Designer and manufacturer of RF amplifiers used in a variety of custom applications in many diverse industries - from Scientific, Medical, Industrial, and Communications and Broadcast.

Custom Designed Photo QSL Cards, Full Color stunning designs, High Quality Printing at competitive Prices. US based QSL designer and printer specialized in custom-designed ham QSL cards.

Custom EMI Filters, AC DC Three phase filters by Filter Concepts Inc.

Product specialist for semiconductors and electron tubes based in Belgium

Ham radio club Decatur Illinois

Located in Upstate New York, specialize in unusual surplus equipment, mostly of military origin.

Quartslab has over 30 years of experience in supplying quartz crystals to the international communications market. Our product range includes the supply of quartz crystals in the frequency range 1.5 to 225 MHz in all popular holder types as well as crystal oscillators in DIL8 and DIL14 packages.

9J2T dx pedition to Zambia 2014 by IDT

This is a standard calculation method that can help you while tuning dipole antennas, by adjusting wire lengths. This method can be used also when you need to add lenght to your wires, and can be additionally used to quarter waves vertical antennas

The Fresno Amateur Radio Club was originally founded in the early days of Amateur Radio as the San Joaquin Valley Radio Club and affiliated with the ARRL on April 5, 1934.

Introduction to ham radio with nice selected pictures and amateur radio history by VK5SW

_AT Auto_ is an automatic antenna tuner designed for amateur radio enthusiasts seeking efficient and reliable tuning solutions. This device automates the tuning process, allowing operators to focus on communication rather than manual adjustments. The tuner is compatible with a range of transceivers, enhancing its versatility in different shack setups. Its design incorporates advanced circuitry to ensure optimal performance across various bands. The _AT Auto_ tuner is particularly useful for those operating in HF bands, providing seamless transitions between frequencies. Its integration capabilities with other shack automation products make it a valuable component for modern amateur radio stations. The tuner supports multiple modes, including _SSB_ and _CW_, catering to diverse operating preferences. Its robust construction and user-friendly interface contribute to its appeal among both seasoned operators and those new to the hobby. Kessler Engineering's focus on innovation and quality is evident in the _AT Auto_'s design. The tuner is part of a broader product line that includes shack automation solutions, reflecting the company's commitment to enhancing amateur radio operations. Despite the website redesign, the tuner remains a key offering in their product portfolio.

This Guide helps you to build the 1:2 BalUn 600 Watts DIY kit step by step. If a delta-loop or quad-loop antenna is powered with a coax cable from the transceiver it is necessary to use a 1:2 BalUn. This 1:2 BalUn uses a symmetrical 1:2 impedance transformer.

Icom 706MkIIG Filters, Make a narrow CW filter work in SSB for the digital modes

Transmitting operations in the 50-54 MHz range offer some unique problems that over the past 50 years have stymied station owners, forcing them to tolerate quiet hours and hostility from family and neighbors attempting to enjoy other electronic services.

Technical details of the Drake R-4C receiver

Amateur Radio related activities of HB9EGA

Hot Springs Village AR

Dedicated to the Indiana D-Star Amateur Radio Users

Isle of Man Repeaters maintained by David Osborn GD4HOZ this site covers the VHF repeater GB3GD and UHF internet linked 70cm repeater GB3IM. Using Allstar software for linking GB3IM is the only site in the uk to have three transmitters. Supported by the Isle of Man Amateur Radio Society

Manufacturer of low cost RF signal generators and portable measuring instruments.

The Pro 95 is a dual trunking handheld scanner designed by GRE and sold by Radio Shack

Software running on the Raspberry PI, Control up to 8 arduino rotators modules, Azimuth maps, Cluster support, Band decoder, contest Web Log, Webcam with RaspiCam support

A technical article that want to explain Coaxial Cable terms, specifications and applications. A glossary of technical terms with clear explanations.

Bucktown Visas and Passports, Inc. processes all of your international documents in as little as 24-48 hours from Chicago, Illinois.

The Tektronix digital multimeter is a feature-rich tool with the accuracy and precision you need for your most demanding measurements.

An interesting article dedicated to hams that want to start learning morse code, including notes on Methodology, online training tools, and a guide to Morse Keys

Troop I, Region 2 - Live Audio Feed Web Player

MikroTik is a Latvian company which founded in 1995 to develop routers and wireless ISP systems. Wifi Routers, router boards, switches, interfaces and enclosures.

Radio programmin equipment, radio programming cables, all sort of cables and connectors, webcams, cameras, security products

Carolinas Chapter of the Antique Wireless Association Inc. "CC-AWA"