Lasersaber strikes again. A joule thief king ?

[TinselKoala]

Hi TinselKoala,
In your video clip, I saw had a ferrite core horizontal oscillations-holding television old. . .
Difficult I found, that can replace the coil with others? . . .

Thanks

The coil is a "loopstick variable inductor". I see that they are getting hard to find. I guess I'm going to have to visit my supplier tomorrow and buy out his stock!

But I think you can make your own. Just take a piece of ferrite for the core, and wind around 100-200 turns of Litz wire on it to make around 9 milliHenry inductance, for the innermost coil. This will be the one with the LEDs across it. Then wind another coil of a single layer of thicker magnet wire on top of that, 20 turns. This is the "magic" coil that does the interesting things. I think it needs to be connected "backwards" in the schematic. Then on top of the whole thing wind another 100 turns or so of thinner magnet wire. This is the coil that is connected to the Collector on one end and the Base Resistor and the Cap (or other supply) + on the other end. 
I think this should work, if you can't find an actual loopstick. If you can figure out some way to pull your ferrite core in and out of the coils, all the better.

[TinselKoala]

Somebody should buy these! I can't afford it.... but these appear to contain the magic Latvian ferrite....

http://www.ebay.com/itm/30-tunable-input-heterodyne-coil-inductor-ferrite-core-crystal-radio-restoring-/141318715946?pt=Vintage_Electronics_R2&hash=item20e7407a2a

[havuhung]

Hi TinselKoala,
yes, I will try to test with a small piece of ferrite rod and can be moved in a paper tube.

Thank you

[Acca]

 Off topic about radio signal amplification using a ferrite loop antenna...

TinselKoala

If you are not familiar with the russian ferrite rods they are very inexpensive  from
the UK..  first link below..


Loop antenna is strange....ferrite rod is

"How can it be stated that an already radiated electromagnetic 'wave' propagates
with an associated transverse magnetic 'field', when electromagnetic radiation is
know to not be a stream of electrons (current) travelling at the speed of light,
whilst additionally, at no point along the 'wave' is there any circuit through which
charge can circulate or flow in order to generate a magnetic field?"

answer ? below:

"Thus the ferrite rod has never been the 'antenna' energising the coil, because it
has always been the antenna coil energising the ferrite rod! 
Electromagnetically radiated radio-frequency photons energise electrons within
the coil;  electron activity constitutes circular charge flow around the coil;  this
generates an alternating electro-magnetic field within the ferrite rod;  which
subsequently energises and aligns the unpaired electron spin gyros within the
ferrite.  Hence a ferrite rod does no more than concentrate the alternating
magnetic field, as generated by photon induced electron flow within the coil, into
aligned electron spins within the ferrite, and via its concentrating permeability, 'Q'
magnifies the voltage transduced by the coil with an improved circuit efficiency
through phase shifted oscillation of resonant energy exchange . "


"extracted and written by Graham Maynard, of UK"

http://www.rapidonline.com/Electrical-Power/100mm-Ferrite-Rod-Aerial-88-3098

http://www.zen22142.zen.co.uk/Media/fsi.htm

http://www.youtube.com/watch?v=iqYZcRXCGxM

http://www.youtube.com/watch?v=qWSqvb9NdLo[/font][/font]

[TinselKoala]

That's pretty neat, but also pretty expensive and heavy.

I've been using a "slinky" spring toy thing for an antenna for my Australia Radio crystal set. It works great! And it's 'tunable' by how much you stretch it out.