My research into this, including cage dipoles, suggests one may realize
little practical tangible effect on SWR bandwidth when replacing a heavy
wire antenna element with a small aluminum tube (where "small" = 1-2
inches in diameter.) Theoretically (I believe) it would have more
impact on higher frequencies a the size of the element increases
relative to wavelength.
There is some discussion of this in the ARRL Antenna Handbook. See page
9-4 and 2-3, et. seq. where it discussed the impact of larger diameter
elements on impedance.
Hope that points in a useful direction.
Happy Trails.
======================= Richards / K8JHR =========================
On 2/3/2011 5:30 PM, Dr. Gerald N. Johnson wrote:
That slow change of the resistive component and rapid change of the
reactive component is much more prominent if you look at the parallel
admittance than the series impedance.
73
|