A bit of a design change to the CoCo ADS-B antenna
Change the whip section at the top to a 1/4 wave section.
Use thin (2mm) slices of spare dielectric to from spacers between element section, to prevent the braid of each section from touching.
Cut the end of the feedline sheath back by 1/4 wavelength, remove the braid and fold back the foil shield. This coax (CTF100) uses a copper foil rather than a metalised film. Form the folded back foil into a
1/4 wave sleeve. Remove the excess dielectric and inner.