Thanks for the tip ! Unfortunately the tuning circuit which was included in my set has only a rectangle coil form.

What also surprised me was the fact that the bar antenna has no litze  wire, only solid copper wire. The same wire was also used in a legacy block.

I thought that the litze  wire has better qualities concerning stray capacitances in HF circuits.

The litze wire is used in the tuning block.

many greetings