Using a 3D printer to make a loading coil for HF portable or static mobile operation.
On Thingiverse I found some files to download and make a loading coil, by VA3TNE, here
https://www.thingiverse.com/thing:2352109
It is designed to work with a folding 'tank whip' or 'Manpack antenna' or AT-271 folding antenna - Google will bring up some useful links.
I printed both the long and short coil versions and found the short coil best suited my needs as it loads the 'tank whip' anywhere between 40 to 10 metres, which is all I need, although the long coil will tune to 80 metres, but it is very twitchy down there.
The coil wire is 1.6mm stainless wire and the end fixings are 3/8in UNF stainless bolts and stainless half nuts and a brass nut - the long brass nut is for old car exhaust manifods and everything can be found on eBay UK and other UK internet sites.
Tuning adjustment is achieved by a sliding 'short' with fly-lead - I used a Stainless 'Jubilee' clip as opposed to the original idea of a 'crocodile' clip, which is why the coil form has 5 vertical cutouts to facilitate the use of a crocodile clip.
The Jubilee clip is tightened enough to just allow it to slide up or down, but not so tight as to clamp it.
I had a broken camera tripod, so dismantled the broken head and 3D printed a bracket to mount the coil and some radials/counterpoise. There are 3 short fly wires on the tripod mount and have gold plated 2mm 'bullet' connections for each of the radials, so they easily pull out if someone steps/trips on a radial and easy to disconnect and coil up for transportation.
How it looks on the tripod for portable work (click the images to supersize)
