Been busy designing (the design is not new but this version is round as opposed to other manufactures square versions) a new style centre-post. Have not yet tested the post but hopefully in the next two weeks I will have it on top of my mast!
SO-239 will be changed to an N-Type socket; this is a prototype purely for testing.

Post OD is 35mm and acts as the outer and a 12.5mm Solid rod is placed inside which acts as the centre conductor.

Centre conductor is suspended on specially designed spacers to hold it central to the outer tubing. The correct description for this system is "transmission feed-line"

All isolators are completely bespoke to each centre-post and are produced on site; this ensures a tight fit every time. Stainless steel coach screw is fitted on the top for attaching the support cords and extra eyelets are an optional fitting for ice support cords. I can supply the cords but customer will be responsible for attaching them.

Initial testing on a VNA is showing a 1:01 SWR and 49 Ohms on 13Mhz to 51 Ohms on 54Mhz when terminated on a 50 Ohm dummy load.

Top of post, The top coach screw is for attaching the support cords to and the eyelets are the optional ice support cord fixings.

GRP spacer, this allows the post to sit in the top flange, it also acts as an additional isolator. The hole is intentional and acts as a drain hole for any moisture build up or water ingress.

Isolation rod, this isolates the stub-mast from the centre-post

More information and pictures to follow.