I pulled my old copy of Terman's Radio Engineers Handbook to see if my
memory was correct and he had a comparison such as you need. He shows 8
charts of Q for various coils on p 75. For 4mhz he shows a 10
microhenry coil using various types of wire. It is 4 1/8 d by 1.6 long
and 8 turns. For 1/8 tubing Q=580, for nr 10 wire Q=500, for nr 18
Q=320, for litz 32-38 wire Q=200. A chart for much lower freq showed Q
as high as 900 at 350khz for a litz coil vs 500 for nr 18 wire. That
coil was 460 microhenry and 6 inch d by 6 inch long. Much more info
there but don't have time to read it, racing against winter to get some
antenna work done.
The QEX for Sept/Oct 2001 has 2 articles on coil Q. One on building a
loading coil for Lowfer communication obtained a Q of 600 at 136khz with
Litz. A second is a mathematical analysis of coil Q and would useful in
designing high Q coils I believe. GL, 73, Dan, N5AR
EVonvaltie@aol.com wrote:
>
> I am trying to find the best way to build RF inductors in the range of 5-50
> uH and the lowest possible losses. They are for use at KW+ power levels, such
> as might be found in tank circuits and antenna matching networks.
>
> I would like to hear any opinions. enlightened or otherwise, in response to
> the following question. For a particular inductor, for use at 3.5MHZ, the
> nominal required coil data is 12turns of #12 wire on a 1.5" form, close wound
> (about +j100 at 3.5). What would be the difference between winding with #12
> magnet wire vs. a Litz weave having the same copper cross section, using
> conductors of approx. 10% of the DIAMETER of the #12 (about .052"). I would
> like to know approx. how much difference there would be in the RF resistance,
> since the coil carries the full antenna current+. Any loss in the coils
> (there are several) subtracts directly from overall antenna gain so it is not
> a trivial issue.
>
> I have found a way to make the Litz wire to my own specs as needed, but don't
> have much to go on for its theoretical performance. I don't recall ever
> seeing any of any value. Have you??
>
> Eric von Valtier K8LV
>
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