After getting utterly fed up with the antenna that came with my CRT One-N, I did what any sensibe person would do: I asked a mate what he was using on top of his Discovery. The answer: Thunderpole Orbitor.
Not the smallest of twigs, the Orbitor stands atabout 160cm (including mag-mount), on top of the already tall Freelander 1. Luckily, the shock coil at the bottom stops it from falling off if you twang it on the occasional tree.
The specs say that it will give an SWR of 1:1.5 over 26-28MHz, as pre-tuned, and to be honest, this is spot on. Both SWR meters, and the nanoVNA confirmed this.
Plus it’s only £17.99 direct from Thunderpole, but that excludes the mounting (3/8″, since you ask). I have to admit that I got mine from Amazon though, and paid over the odds just get get the magmount included and 24 hour delivery. I really was that pissed off with the other antenna!
Note: If, like me you unscrew it to prevent theft/damage, tape a bag over the connection, just to keep it clean!