Hello All:
Over the last couple of years I have done extensive searching for
both theory and practice with regard to loop antennas, and here is
what I have found:
1. Most of the theory is way over my head, since the last calculus
class I took was over 30 years ago.
2. Most practice sites explain very well how to *make* things, but
not much time is spent on *how it works*.
3. There is not much in between, some exceptions are Ian Purdie's
Austrailian site and Rod Elliot's Elliot Sound Products (ESP) site.
Both have excellent tutorials on them. A few ham sites have good
explanations of the connection between theory and practice.
So, what I see is a big blank area in between, and I find myself
going back and forth between the two without a lot of insight being
gained in the process.
For example, there are many sites with formulas for inductance of
solonoid, spiderweb, rook, conical, helical, etc coils, but very
little on distributed capacitance and how it varies with spacing and
wire sizes (unless you want to flagellate yourself with a treatise
on Maxwell's equations).
I would love to use a spreadsheet that included the inductive,
capacitive and pure resistive components of everything from a long
straight wire to coils (as well as loops) as well as most of the
common shapes (circular, square, polygonal). If I had all the
formulas (in an algebraic form, not in differential calculus form) I
would even be willing to put the spreadsheet together and post it to
the group. I am using OpenOffice as my office suite, so I can write
it out in Excel format.
A good starting place is the Dr. Coyle spreadsheet, which I use all
the time. It has formulas for both solonoid and spiderweb designs,
as well as input for capacitance and it will calculate the resonant
frequency for a given inductance, wire size and number of turns, and
gives the physical size of the coil form and length of wire needed.
But I want more. The Qu would be nice, and so would the impedance
(since it does calculate the reactance). I added a table of wire
resistance to the spreadsheet, but at this point I am not clear on
which way to calculate the Q. (I mean, wouldn't the Q tend to
infinity as the resistance went to zero?)
And then there is the distributed capacitance.
I mean, how many Coulombs (sp) does a wire of a given diameter (at
least of copper) have per unit length, given a specific voltage?
And how much of a charge is induced into an adjacent wire a given
length away? And (while I'm on a roll) how fast does the
electrostatic charge collapse at a specific frequency and voltage?
It seems to me that this information could be used to calculate the
capacitive reactance, and therefore the self-resonant frequency of
the coil (or loop). And couldn't one simply multiply the turns by
some constant instead of integrating a complex function from one end
of the coil to the other?
And (Oh, my god!), none of this has taken into account permeability,
reluctance, admittance, etc. for non-air-core devices.
Woe is me and Oy Vey! Where do I go from here?
Any help would be most appreciated.
Barry
