Dyne's LD-F1 (D-O concept) build

[Dyne]

I wonder how a power car antenna does it?

I believe they have a spool that works somewhat like a measuring tape (i.e. flexible enough to coil, rigid enough to extend the antenna without collapsing when unspooled).

My friend suggested something like that, but I don't think I have anything that'd work as the tape (except maybe filament, and even then it'd probably require the spool to have a large diameter or it'd break unless it's nylon). It probably also relies on the tube having a large enough ID for said tape to run all the way to the top, though, and this tubing has a pretty narrow hole, almost too small for the screw attaching it to the retainer.