FBMboomer wrote:
On 10/27/2014 11:59 AM, wrote:
gareth wrote:
Not being one to score points either technically or emotionally, and
always interested in technical discussion, and always prepared to
admit being wrong (when someone illustrates it, rather than just replaying
one of their tape recordings about something completely irrelevant),
there is one thing about the derived formula that shows short antennae to
be poor radiators, and that is that the published physics formulae use as
a basis, the distance of charge movement in proportion to the wavelength,
whereas, as we all know, no charge moves more than just a gnat's cock at
the power levels that we humans are capable of generating and never offer
distances commensurate with even a fraction of a wavelength.
Pure word salad babble.
Start with the fact that there is no "formula that shows short antennae to
be poor radiators" and that in fact physics shows just the opposite.
If that were true why not just have a 1/4 inch antenna to operate on 75
meters? Everyone knows that it would not work. I do not know the theory,
I do know the practice.
Well, if you had been following any of this you would know why.
As an antenna gets shorter in terms of wavelengths the resistive part
of the input impedance goes down.
As a result of this two things happen:
1) The I^2R losses of the antenna increase. This can be reduced by making
the antenna "fatter", that is make it of tubing instead of wire. This
has obvious practical limits.
2) Some sort of matching device is required to match the common 50 Ohms
of a transmitter to the input impedance, which for very short antennas
is a fraction of an Ohm. The matching device is also subject to I^2R
losses and making coils out of 3 inch tubing is not a practical solution
to the problem.
It is NOT that small antennas do not radiate all the power applied to them,
it is the practical problem of applying power to shore antennas.
--
Jim Pennino