I haven't used a discone so far, and I don't know the theory of how they work, that would be a good read on Wikipedia, the free encyclopedia.
"A
discone antenna is a monopole version of a biconical antenna, in which one of the cones is replaced by a disc. It is usually mounted vertically, with the disc at the top and the cone beneath.
Omnidirectional, vertically polarized and with gain similar to a dipole, it is exceptionally wideband, offering a frequency range ratio of up to approximately 10:1. The radiation pattern in the vertical plane is quite narrow, making its sensitivity highest in the direction of the horizon and rather less for signals coming from relatively close by. ..
The extra bandwidth comes from the controlled taper and large termination radius of the cone. The cone shape and flat disk disperse the local electric field. This reduces stored energy in the electric field, reducing antenna Q while also reducing losses."
Something like that would be good on the AM broadcast band for wide band AM and digital, where the SWR can curve up even a few kilocycles from the carrier frequency with regular antennas.
