wrote:
I would like to make it half-size.

Can I just take the full-size dipole and roll the extra copper into a
coil in the center?

de KJ4UO

Sorry, that doesn't work. A length of stretched out wire doesn't behave
the same when it's wound into a coil. The reason is that the field from
one turn of the coil couples strongly to the other turns, while the
field from a straight wire couples only weakly to the adjacent regions
of straight wire. That's why a coil has more inductance than a straight
wire of the same wire length.

The problem with using a simple program to answer your question is that
at that frequency any coil is likely to be a sizeable fraction of a
wavelength long, and perhaps in diameter and therefore will radiate
substantially. So a lumped inductance won't be a good representation of
the coil. EZNEC's helix creation feature would let you realistically
model any proposed inductor and get an accurate answer. Unfortunately,
the free demo version won't have enough segments to do this. You can get
more information about it at http://eznec.com. You could model some very
simple helical inductors of a turn or two with the demo program to get
an idea of how the program works.

Roy Lewallen, W7EL