"NoSPAM" wrote in message ...

"Joel Koltner" wrote in message
...
Thanks for the details, Barry... tell me though, then, is a discone just
a biconical with a ground plane used to create the (image of the) missing
cone?

Yes. It will have less gain than a biconical and the bandwidth is
slightly more restrictive too. But it is much easier to construct!

73, Barry WA4VZQ


All else being equal, a lossless 'ground plane' type antenna, be it a
monopole developed from a dipole or a discone developed from a biconical
dipole, over an infinite ground plane should exhibit 3 dB _more_ gain than
the symmetrical 'parent' form of antenna. This is because its radiation
pattern is limited to half the solid angle of the parent (e.g. only the
space above the ground plane). Then for a given number of watts fed into
the antenna, the power-flux density must be greater in the region where it
can radiate. In practice, the ground plane isn't infinite so there is some
'undercutting' of the vertical radiation pattern, but the gain should still
be somewhat greater.

The apex angle of the cone in a discone can be chosen to yield 50 ohms
terminal resistance over part of its usable bandwidth, and that angle is
different from the apex angle(s) needed in a biconical dipole for the same
impedance. The usable bandwidth is always limited by the limited
flare-length of the cone(s) and usually also by the accuracy of the apex or
apices where termination is made.

Chris