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This project assembles a 49:1 ferrite-core (“FT”) type #43 transformer that matches 50 ohm input to 2500 ohm end fed antenna. It is optimized for 3.5/7/10/14 MHz but will work reasonably well on all amateur bands from 80 meters thru 10 meters with a 135 foot length of wire and a short connection to ground.
This EFHW antenna (patterned after one by Steve Ellington N4LQ, with notes by K1RF), if built carefully, will serve you for many years, and at up to 200 watts. The heart and engineering of its design is in its 49:1 impedance matching transformer, or unun (connects an unbalanced
ARRL and HF Kits offer a 4-band antenna kit: End Fed Half Wavelength Antenna. The advantage of an EFHW is the ease of construction, it’s versatility in a variety of installation configurations, no tuner is needed, and this one works on 4 bands: 10, 15, 20, and 40 meters.
Recommended wire lengths and Installation Notes for Unun models 4932, 4935, 9130, 9132 & 9135. Table shows typical SWR relative to installed wire length. SWR will vary based on topography, proximity of nearby structures, configuration of the antenna wire and choice of ground or counterpoise.
The End-Fed Half-Wave (EFHW) Dipole Wire Antenna By T. W. Longfellow, N7TWL June 2023 Let’s start with the obvious: The purpose of an antenna at the amateur radio station is to transmit and receive radio signals. The type and design of the antenna is based on any number of parameters: specifically, the frequency or
Installing the antenna wire as an Inverted L can change the feed point impedance and may require tuning (changing overall length of the wire) for best coverage of all HF bands. Rows in color are best overall lengths to use for optimum HF spectrum coverage.
Radiation pattern of EFHW antenna is the same as radiation pattern of the Center fed Dipole antenna. That is true only at its first resonance where antenna is half wavelength long just as Simple Dipole antenna. Unlike center fed Dipole, the EFHW antenna can be used on both odd and even multiples or harmonics.
