FM Band Expander Converter, Band Shifter for Japanese Cars Up to 108Mhz (4pcs)

Unfortunately I was never able to figure it out. As a workaround I've got an expander - like this - https://www.amazon.com/Expander-Converter-Shifter-Japanese-108Mhz/dp/B07Q2KXBL1 - but I will keep trying to figure out how it's done!