The discone is in the family of biconical antenna systems. Their design structure is similar to each other. The only difference is the radiating portion of the discone is a disk rather than a cone.
Both have broad banded characteristics, however the discone is advertised as a vertically polarized antenna. I have not found that to be true. It is more horizontal. The biconical is true vertical polarization.
This photo is of a 1000 MHz discone. The vertical shaft above the disk was suppose to be cut off after assembly only leaving enough for the nut to grab the threads to hold the disk in place. After testing the antenna with the extra vertical shaft we found that it inhanced the bandwidth, so we left it in. The total height is about 11 cm, including the BNC connector at the base.
It works well on amateur radio L band (1240-1300 MHz).