Re: re-post of double-tapped primary

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Jonathon,

On 27 Jun 01, at 16:41, Tesla list wrote:

> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> 
> I had an idea, for easy changing of coupling. What if, say you had a
> 15-turn pri. and tapped it at 10. Why couldn't you build a 20 turn pri.,
> tap the outer turn at 5 in from the out side (actually 15) and the inner
> tap at 5 from the inside. then, when ever you wanted to change the
> coupling, you would just move both taps at the same time, and you could
> still change how many turns you have. It would look like this:
> 
>     | | | | *| | | | | | | | | | | *| | | | | O
>             outer tap          inner tap       secondary
> 
> Jonathon

It would work to a degree but it's as well to remember that the inner 
turns have less inductance than the outer turns so you may find slow 
detuning as the taps are moved in until you are at the point where an 
extra turn needs to be added to get back to the original inductance.
    It would work famously with a helical primary. Same difference as 
raising and lowering the secondary in increments of the same height 
per turn. Nice idea.
  
Regards,
malcolm