After few years of sitting on top of my apartment building I decided to bring my Dunax GPN-4B antenna down for repair as top capacitive hat was broken. I found out that there actually no technical details about fixing it. So I went through some work of gathering such information.
First I found out that manufacturer is out of business. Antenna is not in production any more and manufacturer site is down. I asked help from fellow hams, some sent me some info they had, some sent me contact info for manufacturer.I also used my own antenna to take measurements, so finally I got quite complete details that I believe could help other fellow hams trying to repair their own antennas but also ones that want to build similar antenna.