>> Peak currents can be as high as 2100A.
>> 2uH of inductance

> Note that this means the core needs to store 4.4J.  You can play all the
> games you want with turns, wire thickness, core material, etc, but there
is
> no way to escape this basic physics.

It's not obvious what your objections are to what's been asked.
I haven' seen anything that suggests an attempyt to evade "the Physics" -
but rather, a request for help in applying it.
The query seems to boil down to "is there a way that I can use a core
material that doesn't saturate, to increase the inductance for a given coil
resistance wrt an air wound coil so as to reduce the effective resistance?.

This seems to be a reasonable question, and the "first look" approaches that
I have suggested indicate that an eg Micrometals based powdered iron core
may well do the job  OK - and that umetal will quite likely design something
that meets the spec (as the core cost will be hundreds of dollars.

However/also, it seems to me that an air wound core will also be achievable
that works OK.
This page contains an apparently superb calculator that goes beyond the
simplistic formula that I offered.

              http://hamwaves.com/antennas/inductance.html

How good it is is uncertain, and what the target R is is unknown to me, but
it seems that 4 to 6 turns of eg 15mm silver plated copper tube wound in a
(tight ) 100 mm dia spiral with minimum inter turn clearances will produce
inductances of the order required. Resistances appropriateness need checking
but are probably bearable.
They give what seems to be AC resistance (ie skin effect modified
resistance) but I haven't even tried to check for reasonableness.

Plugging in a few figures I get the following.
Use courier or other fixed width font to view:

Dia = coil mean diamyter mm
t = conductor thickness (copper tube)
W - width or coil length mm
N  turns
Rac - resistance impedance at 100 kHz.  ????

N  Dia   t   W  LuH   Rac

4  100  10  50  1.5  .007
4  100  15  70  1.14 .005
4  200  15  70  3.53 .01
6  100  15  100 2    .008

Bifilar winding using eg silver plated 1/8" copper tubing will reduce AC
resistance due to skin effect reductions.

Values are such as to suggest that a handful of small gauge piping, some
silver plating (not expensive) and some playing, should yield an acceptable
result.


      Russell McMahon
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