Antenna Discone

The discone antenna has a useful frequency range of at least 10 to 1. When employed as a transmitting antenna, it is often less efficient than an antenna designed for a more limited frequency range. SWR (standing wave ratio) is typically 1.5:1 or less over several octaves of frequency.
A discone antenna consists of three main parts: the disc, the cone, and the insulator.

The disc:

The disc should have an overall diameter of 0.7 times a quarter wavelength of the antenna's lowest frequency. The antenna's feed point is at the center of the disc. It is usually fed with 50-ohm coaxial cable, with the center conductor connected to the disc, and the outer conductor to the cone.

The cone:

The length of the cone should be a quarter wavelength of the antenna's lowest operating frequency. The cone angle is generally from 25 to 40 degrees.

The insulator:

The disc and cone must be separated by an insulator, the dimensions of which determine some of the antenna's properties, especially on near its high frequency limit.

https://en.wikipedia.org/wiki/Discone_antenna

On the market there are several manufacturers of antennas, some of the best known to radio amateurs, listeners, SWL, but there are also some less known models that are very efficient:

Discone Antennas:

Comet
Diamond
Kreco