[Disclaimer: Any misadventures I have had with this antenna were purely my fault and, in no way, reflect on LNR and their excellent product.]
I bought the LNR EFT-10/20/40 trail-friendly end-fed halfwave (EFHW) antenna about a year and a half ago, after seeing one at Field Day. It’s a great, portable antenna. It packs up small and weighs hardly anything. I often use non-resonant antennas because I like to work a variety of bands. However, I always carry the LNR end-fed in my pack as a backup antenna. The EFT requires some initial pruning before use. This is where my misadventures start.
I don’t have enough real estate at home for antenna testing. Instead, I did the initial pruning of the antenna while setting up for the Skeeter Hunt QRP contest in August of 2015. Trimming an inch at a time was getting a little tedious for me. I incorrectly estimated how much I needed to cut to have the antenna favor the CW section of 40 meters. As you might guess, I screwed up and cut off too much. Resonance was at about 7.110 MHz and frequencies below 7.023 MHz were outside the 2:1 SWR curve. 20 and 10 meters were fine, however. I operated in the contest with no issues.
I resolved to correct my mistake and added that task to my “job jar,” where it languished for the next year and a half. In the meantime, the antenna was used for numerous outings, including a National Parks on the Air (NPOTA) activation of the Appalachian Trail. I just needed to avoid the bottom end of 40 meters.
Fast-forward to this past weekend. I finally got around to doing something about the tuning of this antenna. I had ordered some #26 Poly-STEALTH™ wire from the good folks at Davis RF. First, I measured the top section of the antenna (from the top of the loading coil to the end of the antenna) in its current state. Then I cut the wire about a foot or more from the end. Since the splice wouldn’t fit through the holes in the end insulator, I wanted to keep the splice away from it. I did this if I would ever want to re-tune the antenna for the phone section of 40 meters. I next spliced on a piece of Poly-STEALTH™ wire that made the overall length about 2.5 inches longer than before. After soldering the splice and applying some shrink tubing, I was ready to give it a test in the field.
I was out in central Pennsylvania over the weekend doing some babysitting for my grandson. As I have done at this location before, I strung the EFT-10/20/40 from a second story window to a Jackite pole strapped to the fence in the backyard. The antenna was roughly horizontal and up about 25 feet or so. I wanted to make sure that the range from 7.000 MHz to 7.125 MHz fell within the 2:1 SWR bandwidth. My antenna analyzer showed that it was just a bit long.
After I lowered the antenna and cut off a half-inch, the SWR was pretty much where I wanted it. Now it was resonant around 7.040 MHz and the 2:1 SWR bandwidth spanned 7.000 to 7.130 MHz. On 20 meters, the SWR was less than 1.5:1 across the band. On 10 meters, the SWR was less than 2:1 across the band. The SWR indicator on my KX3 confirmed the results.
At one point, my inner obsessive-compulsive perfectionist said I could cut off another half-inch and make it better. Fortunately, my practical side was able to resist and leave well enough alone. As they say, perfect is the enemy of the good. So, I declared victory and went on to make some nice CW and PSK-31 contacts with my properly tuned antenna.
The antenna works great but that splice will be a constant reminder of what happens when you rush things and try to cut corners.
72, Craig WB3GCK
WB3GCK QRP Amateur Radio 