Let’s hope that all the KX2 owner praise for the internal ATU we read about so often comes from on-air performance and not just the SWR it achieves on tune up. It does in my case.
[Pendant mode ON]
And to all anti-ATU posters there is no such thing as a ‘resonant antenna’. It resonates on a specific fundamental frequency and certain harmonics. So, unless you operate only on or very close to those frequencies or your antenna has a lousy Q, it’s inappropriate to call it a resonant antenna. Therefore, you should refer to an antenna as being resonant on a particular frequency and its harmonics.
As someone who works up and down the band (e.g. CW end and SSB end of 80m) on my multi-band antennas, and who rarely manages to erect the antenna on summit with exactly the same layout, slope angles, etc as when I originally tuned it, I’m grateful to have a good ATU (or AMU if you like) to help compensate.
My usual hf antenna is a modified zs6bkw multiband doublet ie. a 28m dipole fed by about 10m of 300 ohm feedline via a home made Choke balun and the kX3 “tuner”. It is good on all hf bands. Well it’s ok on 10m ssb but not always matchable on the cw end, so I may need a bit of extra length to fix that, it is only .3/28 difference which is less than half a metre. On all other hf bands the kX3 achieves a workable swr below 1.5. On 6m it is usable but swr is 1.8 or more. Adequate for local contacts on 6m.
I’ve used this configuration since about 2021, before that I used the more conventional feedline length of 14m. With that length 30m and 15m were not matchable and no wonder, the feedline would be close to a half wave or a multiple of half waves so the impossible antenna impedance was replicated at the balun end of the feedline. With the shorter feedline it has become a true multiband antenna. (This is not a fault of the basic design as 10, 18 and 24 MHz were not in use when the design was developed)
I know the quarter wave vertical for 20m works better for that band. Also the flowerpot on 10m is better on that band. But for a simple antenna on a 7m pole the doublet is a keeper. It seems to be at least as good as the linked dipole or fan dipoles I’ve used in the past. I use 4mm banana plugs and sockets at each end of the feedline. This allows me to roll up the feedline and carry it in my pack. The antenna is carried on a winder.
having a multiband antenna and a radio with memories for the “tuner” means I can be on 40m but respond within seconds when an S2S opportunity on another band arises. Just tap the spot on Vk portalog and change bands on the radio, make the call, save in log, then return to the original band. No link changing, no need to adjust any spitzensparken, simple. And at 2.6MG activator score its performance speaks for itself. 10-15w on kX3 used almost exclusively. It is also used by VK3PF and Vk2io whose scores also testify to its effectiveness.