# re Basket weave]

**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
*>* radius of
*>* 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
*>* radial
*>* 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
*>* e-mail: cestag@dada.it
*>* url: http://www.dadacasa.com/i5tgc
*>*
*>* -----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
*>* >
*>* >
*>* >
*