Flat Coils (II)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>


> > I may well miss the point here, but I know how to measure Fo of a
>>flat coil and I can explain it to someone else. I can even measure Fo
>>for a slinky.  :)

	Electrical, or mechanical?
	If MEchanical, transverse or longitudinal?

> > I don't know how to make a flat secondary coil.  :(

	Carefully.
	One might consider the comments earlier about 'coreless'
	construction, held together by sealer.

> The latter is easy as, for example, in the case of the spider-weave
> coil which is wound around a slotted form, with the windings passed
> between the slots to support them.  Coils such as this were used in the
> "early days of radio", both because they had a neat appearance and
> because they were supposed to have low distributed capacitance.  I'm not
> sure about the latter, but have such a coil which I wound many years
> ago.  It's about 6" inside diameter, 18" outside diameter, and has an
> inductance of several millihenries.  Q in the 50 kHz region is fairly
> poor.  I know where it is and will try to dig it out and measure it.
 
> Spirals of flat conductors were used among other things because they
> were reasonably compact and it was easy to vary the coupling between two
> of them by sliding them apart or hinging them and moving them as pages
> are opened in a book.  Suspect that appearance was a factor too, as they
> are much harder to make than the solenoidal coils which were used at the
> same time.

	...and i suspect flat coils cool better.  Not significant in
	receiving, can be an issue in transmitting... 
	
> As for any "magical properties" I can only speculate.  As a confirmed
> skeptic I have a strong opinion, but as has been pointed out, "a closed
> mind".
> 
> > Happy day,
> > Ralph Zekelman
> 
> Ed