SATURDAY MORNING BUILDING SESSION
Saturday morning, 10 a.m. – noon
Build A Self-Contained Endfed HALFWAVE Wire Antenna
Cost of kit/instructions: $40
End Fed Half Wave Wire (EFHW) antennas have become the talk of the town, and that’s for good reason. They work! Whether at the home QTH or in the field, an EFHW can be a great antenna — and on Saturday morning from 10 till noon, this year’s hamfest will offer a special opportunity to build a complete and self-contained “EFHW” antenna system!
As you’ll guess from the name, End Fed Half Wave wires are resonant antennas cut to a half wavelength. Typically, their feed impedance is several thousand ohms, and the challenge is converting that to something that a modern radio can live with. Most designs (this one included) assume a feed impedance of about 2500 ohms and use a 49:1 impedance transformer to step that down to something in the 50-ohm range for use with modern rigs. In most cases, no tuner is required for use on the design band.
Our EFHW system consists of the matching transformer unit (built in a plastic case with a clear plastic top) plus an antenna wire holder as well as plenty of wire to make a 20-meter End Fed Half Wave antenna and counterpoise. Yes, the wire’s included! Additionally, the matching unit features an SO-239 female coax connector for connecting to your radio, a nice binding post for connecting the antenna wire, and a captive-wingnut connection post for connecting the counterpoise.
Please note that the matching unit can be used on any band if you connect an antenna that’s an electrical half wavelength in length. Operation on harmonically related bands (for instance using a 20-meter half-wave wire on 10 meters) may be possible, though you might want to use a tuner to even out the variables.
Built using an FT140-43 core, the matching unit you’ll build is conservatively rated for 50 watts CW or 100 watts PEP SSB. Of course, you’ll need to derate it if using digital modes.
The kit includes all parts and hardware needed to build the matching unit, plus an antenna winder and antenna and counterpoise wire for 20 meters. Also included are detailed and fully illustrated instructions.
Sign-Up Here: On This Google Form
Note: Each Antenna Project has its own sign-up page. We have set a limit of 12 for each antenna build but are allowing 16 to sign up just in case of no-shows.
Return to: The Antenna Build Project Page