I recently posted about end-fed antennas. That post basically criticized the seller of the “QSO King” antennas being sold on eBay. What he’s selling isn’t really what most hams think of when they think of an end-fed antenna.
What do most hams think about? For most hams, an end-fed antenna is and “end-fed, half-wave,” or EFHW, antenna. That is to say that the antenna is the same length as a half-wave dipole antenna. When the feedline is connected to the center of a half-wave antenna, the feedpoint impedance is theoretically 72 ohms, which is a good match to both 50-ohm and 70-ohm coax and the 50-ohm outputs of most ham transceivers.
When the feedline is connected to the end of a half-wave antenna, the situation is quite different. At the ends, the impedance is thousands of ohms. To connect a feedline there, you need some kind of matching device. This matching device transforms the impedance from 4,000 or 5,000 ohms down to 50 ohms.
If the impedance is so high, why would you want to use an end-fed, half-wave antenna? Well, for one thing, it’s sometimes easier to connect a feedline to the end of an antenna instead of the middle. It also makes the feedline much shorter.
With that in mind, here are some links to other resources on EFHW antennas:
- LnR Precision. LnR now sells the Par EndFedz line of antennas. These are hundreds, if not thousands, of these antennas out there, and I’ve never really heard anything bad about them.
- AA5TB.Com. AA5TB has a bunch of pages on the EFHW antenna, most notably articles on different couplers and an article on the basics of the EFHW antenna. He’s also posted a spreadsheet to help you design your own EFHW tuner.
- KC8AON’s 40 – 12 m EFHW Tuner. Most EFHW couplers are for a single band. This QRP coupler can be used with half-wave wires from 40 m through 12 m.
Elwood Downey says
I’ll put in a good word for the AA5TB site. I built a 40 m EFHW according to his information. Tuned using his procedures (basically resonate the tank circuit first with a resistor) I can confirm little or no counterpoise at all is required. Very convenient.
Duane Neese says
I bought the QSO King antenna you were talking about in your article about 3 years ago. I installed it according to the instructions and it works fantastically. I R/T on all bands including 160MHz. I cut the antenna to 107 ft. I also bought his RF choke and installed it below the balum. I checked the antenna with my analyser and found no band higher than 10/1 SWR. No problem for my Icom 7000 with its IT-100 tuner. I used LMR 400 coax about 70 ft in length. The antenna is about 30 foot off the ground. No radials. I have made contacts from my home (Kentucky) to all over the world. No matter what you call it, The antenna works GREAT. 73, KK4NVC
Raymond Sult says
I use that same antenna (QSO King) bought on eBay in 2013 or 2014. Works AMAZINGLY WELL ! Performs WAY better than I had expected. I use it with an in-expensive MFJ 971 tuner. 100 watts PEP on my iCom 718 and about 90 watts on my Alinco SR8. One end is 12 feet off the ground and it slopes up to almost 24 feet at the far end. Using about 80 feet of copper wire.
Earl Moreo N6FXB says
Ok, desperate for info. Google lists zero references for the following search:
Gain of 1 wave length end fed wire antenna.
I need the info because DARA (Hamvention and all that) will be characterizing a 1 meter on a side vertically polarized reentrant rhombic, and I need to be able to show just where a rhombic gets its gain.
BY the way, Google finds essentially one reference, since the several it finds are essentially the same article, on Rhombics in general.
Jeff bernard says
The different swr you had with the same type of cores could possibly be the permeability of the core the required permeability changes with the frequency find a happy medium. KC8KAA