From: "Hans-Joachim Brandt" <hajo.brandt.dj1zb@t-online.de>
To: rsgb_lf_group@blacksheep.org
References: <000a01c16187$aec96d00$49c928c3@ericadodd>
Subject: Re: LF: Multi-layer loading coils
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Date: Wed, 31 Oct 2001 01:46:52 +0100
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Dear all,

concerning multi versus single layer coils I have been informed by DJ2EY who 
employs two coils of different diameter as a variometer that the Q of the total 
coil is less when the smaller coil is fully immersed into the greater one. It 
seems that the metal of the inner coil increases the loss of the outer coil (and 
possibly vice versa).

Therefore when a high Q is needed, a single layer coil would be the better 
solution.

HW?

73 Ha-Jo, DJ1ZB  


g3ldo schrieb:
> Some time ago I obtained a Decca loading coil on one of my visits to the
> Crawley radio club. The Decca coil on page 64 of the LF Handbook illustrates
> the general construction of one of these coils and the Decca loading and
> matching system is shown on page 13. The Decca system used five transmitters
> multiplexed (if this is the right word) into a single transmitting antenna
> so the coils are quite complex, comprising several separate windings wound
> using a low capacity basket
>  weave on the same former.
>
> The purpose of this exercise was to see if this coil might be suitable for
> amateur LF. For the coil to be of any use it would have to be completely
> rebuilt.
>
> There seems to be two different types of construction. The one shown on page
> 84 of the LF book is an older type, which uses Perspex formers and are fixed
> in place using an adhesive. This means that it is very difficult to
> dismantle without damage. Furthermore the Litz wire is difficult solder -
> you have to use methods as described on Page 84.
> The later coils use a former ribs made of plastic using a sort of Lego
> construction, which is held in place by the wire itself. Furthermore, the
> Litz can be soldered by just dipping the end into a solder pot (after first
> removing the plastic outer insulation).
>
> The coil was easily dismantled in an afternoon and a finisher up with a
> large plastic box of Lego bits, about 25kg of Litz and a basic coil former
> comprising a hard plastic cylinder 449mm in diameter and 220mm long.
>
> As you can see from the photo, the coil will have to be multi-layered. Is
> there any performance penalty in using such a method of construction
> compared with using the straight single layered coil?. One problem that
> occurs to me is the potential gradient across the coil but I know how to
> avoid any difficulties in this regard.
>
> I wish to thank Dick, Rick and Andy for multi-layer coil formula. At the
> moment I think that  empirical experimenting is going to be the only way of
> obtaining any useful information. Has anyone else got a Decca coil and have
> they tried using it?
>
> Regards,
> Peter, G3LDO
>
> e-mail <g3ldo@ukonline.co.uk>
>
> Web <http://web.ukonline.co.uk/g3ldo>
>
>
>