"Jim Lux" wrote in message
...
Michael Coslo wrote:
While looking for a way to get a little more bandwidth out of an 80 meter
antenna, I mocked up an antenna in EZNEC that was thick. I plan on making
an antenna with spreaders and run 4 wires on each leg of the dipole.

I emulated this in EZNEC by simply making the wire thickness quite thick,
ranging from 4 inches to a foot.

The interesting thing was that as the thickness increased, the antenna
length decreased for min VSWR.

Is this a real thing?

yes.

It's often explained as "extra capacitance from the bigger size", but I
think that's not what's really going on.


The effect is clearly shown in Hallen's curves which appear in many of the
standard text books (e.g. Jordan & Balmain, Electromagnetic waves and
radiating systems). There's certainly a likelihood of greater shunt
capacitance at the feed point, but if the limbs are made conical - radiating
geometrically from the feedpoint - then this doesn't apply. In that case,
Schelkunoff might be of some help.

Chris