On Tue, 26 Oct 2004 11:51:10 GMT, "Knarf"
wrote:

The difference
between the lumped element and distributed inductor is significant, although
the gains are almost identical from both models.

Hi Frank,

You've hit the nail on the head (although I've seen it claimed it
makes a 12dB difference!).

Rarely do we get any practical correlation from this "sky is falling"
oops "current is dropping" argument.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Tue, 26 Oct 2004 11:51:10 GMT, "Knarf"
wrote:

The difference
between the lumped element and distributed inductor is significant,
although
the gains are almost identical from both models.

Hi Frank,

You've hit the nail on the head (although I've seen it claimed it
makes a 12dB difference!).

Rarely do we get any practical correlation from this "sky is falling"
oops "current is dropping" argument.

73's
Richard Clark, KB7QHC

Hi Richard,

Cannot see where anybody could get a12 dB difference, since you can only
model a lumped element inductance, you could not build it to test the
performance. I have spent many hours this past week modeling short, loaded,
monopoles, over a perfect ground -- triggered by the previous thread -- just
to see what results I could get. An 86.5" vertical, center loaded, with a
lumped element inductor resonating in the 21 MHz range, exhibits an input
impedance of 20.91 Ohms, and a maximum gain of +4.754 dBi. The same antenna
with a distributed 12 turn helix, of 2.5" diameter, and 6" long, has an
input impedance of 18.98 Ohms, and a gain of +4.783 dBi. The helix alone
has a gain of -25 dBi. Transcribing the NEC output file to an Excel spread
sheet produces some very interesting current plots.

73,

Frank

Richard Clark wrote:
Rarely do we get any practical correlation from this "sky is falling"
oops "current is dropping" argument.

Asserting that the argument is about any practical correlation is
a diversion of the issue. THE ARGUMENT IS ABOUT THE CURRENT IN A
LOADING COIL, not about the radiation pattern. The radiation pattern
is completely irrelevant to the argument. One side says the current
is absolutely constant except for radiation. The other side says it
is not constant (except for special cases). An electrical 1/4WL loaded
mobile antenna is not one of the special cases.

Nice attempt at changing the subject - didn't work.

In the process of learning why the superposed current is not constant
through a loading coil in a standing-wave antenna, you will also learn
something about standing-wave antennas in general.
--
73, Cecil http://www.qsl.net/w5dxp


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