This is a VHF J inside a PVC tube. It has a low 'profile'. Note that the stub length change inside the PVC (the l/2 not) regarding a J in the free space. Coax feed is 2 cm above bottom. The l/4 length is 46 cm. The l/2 length is 97 cm.

 Please notice that some PVC tubes have graphite inside them. A good test is to put a small piece of the PVC with a glass of water together to a microwave oven to see if it become hot. If is become very hot it has graphite inside.

Update: using white PVC tube SWR do not change as the antenna is inserted. Only the feed point needs a little adjustment. The final dimensions I use is 94 cm for the L/2, 48.5 cm for the L/4 and feed point is at 3,5 cm. In this antenna a RG58 cable it was used.