litz vs. regular wire...
Thu, 13 Apr 2000 15:20:25 -0400
Peter Dodd wrote:
> > G4JNT> Both coils were the same diameter, same inductance, and roughly
> > the same length in total. So why was the one made of plain
> > wire better ? Self capacitance ?
> Gamal> No. Unless the "capacity" exhibits significant dielectric losses,
> > great self capacitance does not harm in lieu of Q.
> > What you probably have missed is to keep distance between
> > individual turns of the coil's winding. The effect of closely
> > winded turns is named proximitty effect. Current in one turn
> > tends to displace the current in the adjacent turn and vice versa.
> > When constructing loop antenna windings, I try to keep a clearance
> > of at least 2 times the wire diameter in between individual turns and
> > always get optimum Q. For solenoid type of coils I recommend a minimum
> > of 1 wire's diameter of clearance.
> > As the self-made Litz wire has a greater outer diameter, it's
> > relative close proximitty to the next turn reduces Q much more
> > than in the case of the solid wire.
> I use a 400uH commercial variometer in series with my main loading
> coil for tuning. This single layer solenoid coil is wound with Litz
> wire and the spacing is about 1.5 wire diameter.
> The main loading coil is wound on plastic fencing material formed
> into a cylinder. It was not possible to maintain a one wire spacing
> so I compromised and wound the coil in 'bunches' of 10 windings.
> A lot of effort goes into the design of professional LF coil design,
> to reduce adjacent wire proximity while retaining a managable small
> size as can be seen in the design of the Decca transmitter coil
> formers (hopefully, more will be reveilled when I can figure it out).
> Fairly complex coil design articles appeared in early publications,
> which described basket and honeycomb winding patterns.
> I will try to get some of this into the next edition of the LF Book -
> the main problem is the illustrations!
> Regards, Peter, G3LDO