Re: 3-1000z coil, more questions

["Finn Hammer" <f-hammer-at-post5.tele.dk> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Ross!

I noticed on your schematic, that you are aware of the need to turn the
filaments on, before applying plate voltage.

Here is a clever arrangement of 2 DPST switches, ensuring that no matter
switch is thrown first, the filament transformer is sure to get the
juice first.

  Please view in a fixed-width font such as Courier.


                          ./
                          /
                   o----o/.   0------------o
                   |      ./               )
                   |      /                )
                   o----o/.   0-o          ) Plate Xfmr
                   |            |          )
                   |            |          )
                   |            |   +------o
                   |      ./    |   |
                   |      /     |   |
                   o----o/.   0-o--- )-----o
                   |      ./        |      )
   o---------------+      /         |      )
                        o/.   0-----+      ) Fil. Xfmr
                        |                  )
    Line in             |                  )
                        |                  )
   o--------------------o------------------o


Hope you will find it usefull.
Cheers, Finn Hammer

(Who snipped this arrangement from Sound Practices Vol.2 #1 )

Tesla list wrote:
> 
> Original poster: "Ross Overstreet" <ross-o-at-mindspring-dot-com>
> 
> Hi Malcolm (and gang),
> 
> I measured the wire diameter at 0.021" with a micrometer.  I guess
> experimental results of 400Hz and a theoretical of 375 isn't too bad
> (6.25%).  I'm just spoiled since my previous coils came out so close...
> 
> As the schematic indicates, I wanted to try filtered DC for the 1st mode of
> operation because I eventually want to audio modulate it and I think the ion
> motor trick is neat.  I'm not completely sold on DC and could just as well
> start out with AC or level-shifted.
> Are there logical reasons why I should try one before the others?  Maybe
> straight AC because it has less components?
> 
> I'm still reading the responses and trying to process all the info...
> 
> David - I have about 12 of the panasonic MMC's laying around.  I'll make a
> single string out of 'em and get the C down around 4.6nF.  That will drop my
> primary turns down to around 13.5.  The primary tank DOES have to oscillate
> at the same freq as the secondary, right?!?
> 
> I'm making the grid coil so that it can easily slide up or down the primary
> former to adjust coupling.
> 
> Thanks for the help!  Hope I'm not wearing on anyone's patience with this
> thread b/c there are more questions to come.  I'll try to put up fresh pics
> every major step in the construction to keep things from getting too boring.
> 
> Seeya,
> Ross
> 
> ---Ross wrote---
> > 1.  My secondary is 4" x 23 5/8", wound with 0.021" magnet wire, and has a
> > measured resonant freq of 400 KHz.  (This is surprising b/c Medhurst &
> > Wheeler predict it to be 375 kHz)
> 
> ---Malcolm replied---
> How many turns are actually on it? The 0.021" is the copper
> diameter, not the outside diameter of the insulated wire.