RadioBanter - View Single Post - Current in antenna loading coils controversy

October 30th 03, 04:44 AM

On 29 Oct 2003 18:58:40 GMT, oSaddam (Yuri Blanarovich)
wrote:

It looks like this factor is not properly accommodated in modeling programs
using loading inductors in antenna elements. In view of the above, time
permitting, I will try to do some work and try to shed some more light on the
subject.

Hi Yuri,

With respect to the data:
Here are some actual measurements of current below and above loading coils.
92" mast, using a HI-Q coil (openwound airdux, 2 1/2"d) with small thermocouple
type meters mounted on the insulated coil support. First for 40m, moving the coil
in the mast from base to center to top (with hat) and reresonating.
Base --100ma below & 66ma above
Center --100ma below & 45ma above
Top --100ma below & 37ma above

This speaks more of simple Resistive heat loss supported by your own
direct observation of:
I fried the loading coil with 600W into Hustler resonator,
melting heat-shrink tubing and wire at the bottom of the coil.

As you, through personal testimony, offer that the bottom of the coil
was warmer (hotter even) than the top; and further, given that the
measuring device is caloric based (thermocouple) it stands to reason
that the close association to heat inflates the base reading not
through the evidence of higher current, but higher (and demonstrable)
heat. The pictures show the close proximity of the thermocouples to
the heat source/coil and also reveal no readings at greater distances
from the coil.

You go to great lengths to portray the current distribution along the
entire length of the radiator from authoritative sources, and yet you
do nothing to confirm them; except over the small portion that
fascinates you and is prone to just such systematic error as I
describe.

73's
Richard Clark, KB7QHC