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Question on using a built in ATU to tune up a random wire on 60m/80m

I have historically used the LNR 10/20/40 Trail Friendly antenna for most/many of my activations. It’s a common solution in the States.

However, yesterday Gerald (G4OIG) was using a dipole for 60m, 40m and 30m with a lot of success on 60m and BTW we had a blast on our two activations…lots of fun.

The Elecraft documentation for the KX3 and KX2 mention using the tuner in conjunction with a random wire tossed in a tree with one plus wires acting as ground radials thrown out over the ground.

Does anyone have any guidenace, experience etc on using a random wire, radial combo with a rig based ATU on 60m and 80m?

I could spring for another end fed, guess I could even build one but am intrigued if the ATU and wire solution will work. It seems deceptively simple and ideally light weight.

Here is my End Fed doing me proud yesterday on 40m atop Black Hill near Melrose. Windy, very windy but really nice when it wasn’t windy…did I say windy…

Paul M0SNA / W6PNG

Hi Paul,

For a few months I experimented with a random long wire configured as an inverted L (22m horizontal at about 8 to 9m high with 4m sloping to a 9:1 UnUn on the lawn; UnUn on short wire to ground stake and 10m RG174 feeder back to the shack). Here are the VSWR figures using FT857 with and without a Z11 Pro ATU…

160 1815 1835 1845 1910 1995
off 4.0 4.0 4.0 4.0 4.0
on 1.3 1.2 1.2 1.4 1.8
80 3505 3540 3580 3605 3700 3795
off 5.0 6.0 7.0 7.0 8.0 8.0
on 1.7 1.8 1.9 1.7 1.6 1.4
60 5260 5300 5325 5355 5375 5405
off 10.0 12.0 14.0 16.0 16.0 16.0
on 1.3 1.5 1.6 1.8 1.9 2.2
40 7005 7030 7060 7100 7150 7195
off 3.0 3.0 2.8 2.6 2.6 2.5
on 2.2 2.5 2.6 2.6 2.4 2.3
30 10105 10130 10145
off 3.0 3.0 3.0
on 1.3 1.3 1.3
20 14005 14050 14095 14130 14200 14345
off 7.0 7.0 7.0 7.0 7.0 7.0
on 1.5 1.7 1.9 1.6 1.4 1.2
17 18070 18095 18115 18120 18140 18165
off 2.1 2.1 2.1 2.1 2.1 2.1
on 1.6 1.6 1.6 1.6 1.6 1.6
15 21005 21070 21120 21155 21300 21445
off 1.2 1.2 1.2 1.3 1.4 1.5
on 1.2 1.1 1.1 1.1 1.2 1.4
12 24895 24910 24935 24945 24985
off 1.1 1.1 1.1 1.1 1.1
on 1.1 1.1 1.1 1.1 1.6
10 28005 28070 28190 28325 29000 29695
off 1.2 1.1 1.1 1.1 1.1 1.4
on 1.2 1.1 1.1 1.1 1.1 1.3
6 50005 50050 50095 50105 50200 50295
off 3.0 3.0 3.0 3.0 3.0 3.0
on 1.5 1.4 1.4 1.4 1.3 1.3

I replaced the RLW with a homemade halfwave 80m dipole for portable use (very thin wire, 1:1 balun and 10m RG174 feeder). My KX2 internal ATU flattens the non-ATU VSWR U-shaped curve across the whole band. Here’s the VSWR without ATU …

The 80m dipole also loads well on higher bands using the KX2-ATU and I’ve had good to excellent reports on SOTA summit activation on 60, 40 and 30m as well as 80m using QRP CW.

I adapted my Sotabeams 40/30/20 tri-bander linked dipole adding extensions for 60m. Dependable all-rounder on all those bands with best results compared to the other antennas (except for 80m).

I also have two LNR Precision EFHWs: EFT-MTR 40/30/20 (19.8m long) and EFT-10/20/40 (12.5m long). Excellent VSWR with the KX2 and signal reports but usually not as good as the linked dipole.

In summary, the KX2 ATU loads a wet piece of string but all the above antennas also radiate well.

73 Andy

I have had good luck with a 58’/13’ wire arrangement tossed into trees when not running an amp this year. Internal tuner tuned it nicely 80-20 metres.


Just a datapoint, but my KX3 tunes up 35.5ft or 41ft end-fed (plus un:un and 25ft coax… no separate counterpose) no problem on 60m/80m. Longer would certainly be better for efficiency, but in a pinch it works. 2 weeks ago I did have a K7MK-to-K7VK S2S on 80M (Utah to Montana) on the 41ft. Not sure what Vic was running, but it worked. If I was going to make a habit of it, I’d probably go with one of the longer end-fed lengths (58, 71, etc). Note, I think the next length (online endfed recommendations) is 85ft, but they usually don’t show 60m. Since ~84ft is a half-wave on 60m, maybe that is a length to avoid (high impedance?). So, adding 60m into the mix does add some theoretical impedance challenges, but with KX3/2 you can tune up just about anything. My current setup is 41ft 26g poly stealth, home-brew 9:1 in dental floss container (wg0at inspired) and 25ft RG-174. For support I use the 4.1m mini-sotabeams pole. I have a fishing swivel at the ~4m point of the radiator to attach to the top of the pole and then I slope the remainder out. YMMV. If nothing else, you’ve inspired me to give 60m a go from a summit. Doesn’t look like there are any USA 60m skimmers to get data from though. I guess endless CQ’s will determine if I am getting out or not! GL de K7MK

G day Paul I did use for SOTA and also chased SOTA from my back yard using several end fed random wires with counter poise wires. A good one or two ended up being 81 feet or 53 feet for the radiator with about 9 feet and 29 feet for counter poise. That was before I needed to use 80m to work my closer in chasers with the down turn in band conditions here in vk5. But back in the better times I did have a few S2S to Europe on the 53/9 foot end fed wire on an 8m squid pole. I messed with length combinations until the kx3 was happy to tune the antenna then worried after if anyone could hear me and found the two length combinations that seemed to work best for both tuning and being heard by as many chasers as possible. Sorry I don’t have any experience with 60 m we are not allocated that band in vk so can’t report on that band. The last 3 years I have been activating on 80 40 20 m so these days I use a 20/40 m link dipole with clip on extensions for 80 m not game to hike in to a summit with an end fed after an activation nearly failed with only 1 cw hf qso and saved the day with 3 locals on 2m simplex. I consider the link dipole inverted V the best SOTA antenna from 6 years experience activating.
Regards and good luck
Ian vk5cz …

I sometimes use my KX2/ATU with 53ft wire to a 9:1 UNUN and a 6ft length of RG58 to the rig. I intentionally keep the coax very short and use the bigger size RG58 to minimize SWR loss in the feedline, which will be several dB worse using longer lengths of RG174. The antenna seems to get out like gangbusters on 60M-17M. It also tunes 80M fine, just haven’t tried to make a QSO there. I had over 60 RBN spots for today’s activation.

The 53ft length seems magical - I’ve tried shorter lengths and they were okay/not great. I rely on the coax braid to provide counterpoise.

Barry N1EU