Andre' Kesteloot akestelo@bellatlantic.net
Sun, 13 Aug 2000 15:02:07 -0400

```cesare tagliabue wrote:

>      Hello Alan, John & others
>  Yes, Alan, the given Wheeler formula is valid however for a single spiral,
> unfortunately I've never found specific tools for calculate a multi-pie
> coil. An alternate
> way to roughly evaluate the inductance of such a coil is to regard it as a
> normal
> multi-layer coil with turns regularly distributed in its cross section and
> use another
> formula by Wheeler: L = 0.8 a^2 N^2 / ( 6a + 9l + 10c ), where a= mean
> winding, l=length of coil and c=radial dimension of pies, obviously in
> inches.
>  If the radial dimension of pies is small compared with its mean radius and
> the coil is made with a large number of pies, so its length is considerable,
> there is
> another approximate formula: L = a^2 N^2 / ( 9a + 10l) - c a N^2 / (10 pi
> l), where
> a,l,c are the same as in the previous one and pi = 3.14. I don't know what
> is more
> accurate but I believe both are enough good for solving our problems. If the
> dimension of pies is small, that is no many turns each, the space between
> pies
> may be also small being the voltage quite low and the effect of the
> capacitance
> negligible, so the coil may result very good in terms of high inductance,
> low self-
> capacitance and therefore high Q.The basket weave coil shows a significant
> reduction of the proximity effect, so lowering the RF resistance and the
> self
> capacitance as well.
>  Criticisms are welcome   73  Cesare
>
> Cesare Tagliabue   I 5 TGC
>
> -----Messaggio originale-----
> Da: Alan Melia <Alan.Melia@btinternet.com>
> A: rsgb_lf_group@blacksheep.org <rsgb_lf_group@blacksheep.org>
> Data: sabato 12 agosto 2000 23.33
> Oggetto: LF: re Basket weave
>
> >Hi Cesare thanks for that formula. The trouble is it doesnt help with
> >multi-pie coils, though I suspect you could just use mutual inductance
> >formula. I am hunting in old books of nomographs to see if there is
> anything
> >in them from the 1920s and 30s.
> >
> >I have also dropped Reg G4FPQ an e-mail to see if he has anything.
> >
> >Cheers de Alan G3NYK
> >Alan.Melia@btinternet.com
> >
> >
> >

```