Thanks Marek, for your information! The KN5L method looks really interesting, maybe I'll try it with a core I have at hand.
Some days ago, I received the ATU-10 from the Aliexpress Uptech Store. I checked it on the bench and all seems fine (I didn't even had to open it).?
Today I experimented with the ATU-10 on a summit, but to summarize, I wasn't convinced, mainly because of the small tuning range. But also how to quickly mount it on the telescopic pole and other small annoyances that I'm not used to.
I have to think about a different setup.
73 Stephan
HB9EAJ