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Re: 3-1000z coil, more questions
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
Please view in a fixed-width font such as Courier.
| ./ )
| / )
o----o/. 0-o ) Plate Xfmr
| | )
| | )
| | +------o
| ./ | |
| / | |
o----o/. 0-o--- )-----o
| ./ | )
o---------------+ / | )
o/. 0-----+ ) Fil. Xfmr
Line in | )
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.
> ---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.