Steel Core elements

The recent discussion on insulated elements reminded me of the 4L 20M quad
that a friend of mine built 25 years ago. It probably used TW back then
(rather than THHN). It was so badly detuned that it didn't work at all
until he stripped off the insulation.

But this thread is also relevant to an issue that I recently discussed with
Brian Beezley. What effect does the steel core have on VF and loss when
making dipole elements from Copperweld. There is both a 30% and a 40% grade
of copperweld (at least there was 20 years ago when I last looked into it).
For one, I believe that the ferromagnetic core would tend to push the
current into the outer surface of the antenna, resulting in increased skin
effect and increased loss. And there may be additional losses due to the
steel core.

The large MF/HF arrays (1.5-30 MHz log periodics) that I have constructed
from copperweld have all seemed to work pretty well, but that is pretty easy
with a LP design and the losses weren't apparent as heating due to the
pulsed nature of the transmitters.

Does anyone have any quantitative data or even gut level feeling for this
effect, especially in the MF and HF region. I am anticipating building some
large arrays with wire spans of up to 100 meters, including 60 or 70 meters
of feedline that needs to be supported from the center. Copperweld sure
looks like the only answer from a mechanical standpoint, but I hate to incur
any serious losses.

Thanks, John (W0UN)

John Brosnahan
La Salle Research Corp 24115 WCR 40 La Salle, CO 80645 USA
voice 970-284-6602 fax 970-284-0979 email broz_at_csn.net
Received on Tue Feb 06 1996 - 01:54:00 EST