The 2 inch OD metal pipe for the DX Engineering 43 foot vertical antenna needs to be in the ground about 34 inches.
We made the hole about 36 inches deep with the idea of putting in two inches of gravel for the bottom of the pipe to rest on.
In retrospect, it probably would make sense to pour a few inches of concrete only at the bottom. However, we didn’t so we just poured in some gravel and proceeded.