Here is a design for a 446 Mhz band outside aerial with ground planes.
The aerial is built on a SO259 chassis socket, with small nuts and bolts to hold the ground planes on, after the ground planes are attached, and the vertical element is soldered in, it is worth putting Araldite over the ground plane bolts, so they cant work loose in high winds.
The whole assembly will fit into a piece of 1 inch/25mm plastic tube to allow it to be fitted to a mast, or other fixing. The plastic tube requires a few saw cuts down the top, so a jubilee clip can be tightened onto the coaxial PL259 plug. It is well worth using the better grades of low loss cable on the aerial. The aerial will be resonant about 446.2 MHz, but it would be worth checking with a VSWR meter before transmitting. I have used this design for years on 70cm band, and you will be surprised how well it works.
Brass brazing rod is really easy to solder, and easy to get.