According to the linked page the wind vane will mount on either the Mentz or the Shakespeare antennas with the thin 3' stainless whip.
That's pretty much the standard type of antenna used on sailboats - a three foot 1/2 wave 3dB gain antenna with a coil at the bottom and a stainless whip, for example the Shakespeare 5215 "Squatty Body"
You can get higher gain antennas, and longer antennas. But on sailboats, you want the rounder transmission pattern of a 3dB antenna in case you are heeling over, and you already have plenty of vertical height at the top of the mast, 30-50 feet in the air, so 3' is plenty of length.
Cool device, BTW, I put it on my wish list for when I replace my antenna.