It is easy to homebrew this ¼ λ ground plane antenna for 70cm. All one needs is a TNC connector (see inset), 1.6mm brass brazing rod and a pack of ‘M-Seal’(epoxy sealant in dual component lump form).
Radiating element length in inches is 2808/f MHz minus the projecting length of the TNC hot end.
Radial length in inches is 2950/f MHz plus a little for soldering on to the TNC connector flange.
The soldered points are sealed against water ingress using M-Seal.