Quote from: Jdo300 on August 17, 2007, 11:07:06 PM
Hi Eldarion,

I can answer that question right off the bat. That neo magnet you have for the core is overpowering ALL of the fields from the coils that you are applying. The whole point of the low voltage DC bias is to turn the 2D rotating magnetic field into a 3D vortex field but this also implies that the rotating field must be strong enough to influence the bias fied. Most Neo magnets have a B-field strength of over 2000+ gauss so there is NO WAY you could setup a vortex in a field that strong without having field coils of comparable strength.

So in other words, that big magnet is choking your whole TPU. If I were you, I would replace that magnet with something like a ceramic 5 magnet, whose field strength is much easier to perturb than the Neo.

God Bless,
Jason O

Jason,

Thanks for confirming my suspicions--I was afraid of that!  It is extremely difficult scrounge up a core that is even close to the correct parameters.

I was doing some poking around, trying to learn more about core materials, best materials for a given application, etc. and came across this page: http://www.w8ji.com/core_selection.htm  There's a lot of good information there--I came across this little gem: A low "turns count" is a good indicator the correct core size and core material is being used.

This is very important to keep in mind--more turns is not always better.  I was always under the impression that more turns meant more power transfer, better flux transfer, etc. but it looks like I fell into a common misconception!

Eldarion

Hey Eldarion,

Nice link there. I only understodd about half of what I was reading but it was quite informative.

@Everyone,

I found a simple way that we can monitor the voltage on the output coil for testing purposes. I checked around on eBay and there is a nice selection of PC interface multimeter's that we can use. So all we need to do (if we are using a programmed approach) is do frequency sweeps and  record via the multimeter the output voltage. This would allow us to automate the frequency tuning process, especially when fine tuning the phases.

http://search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=PC+multimeter&category0=

God Bless,
Jason O

picture of my ring.

just have to add the bias stuff.

@Jason,

QuoteI've still been doing some digging around for the perfect control circuit and I found what I believe to be the ULTIMITE IC for the job. It is called the AD9959 which is a 4-Channel 500 MSPS DDS
with 10-Bit DACs. Basically, you have 4 independent, synchronized sine wave generators that can potentially go up to 100MHz all in a single IC!!! Each channel is programmable which means we can use any microcontroller (doesn't matter how fast) to set the frequencies, amplitude, and phase shift for each channel!

Yes, I think this chip has been discussed quite a lot a few weeks back but you must have not seen the posts.
Soldering it does not worry me too much, its etching the PCB with such fine tracks that concerns me.
Re-work soldering can be done using a 20x microscope, 0.5mm solder wire, 0.4mm tip soldering iron.
I will see how I get on with the DDS 20 function gen., I may look at this route too.
Its programming a microcontroller to get it to work thats going to be the challenge.
But at the end of it you will have a unique bit of kit that cannot be bought off the shelf.
The sine wave output can be fed into a high speed comparator to give you a variable duty pulse.
Just vary the bias on the comparator to get the desired pulse width.
Looking at the number of people that are keen on using this chip then maybe its worth putting together all the bits to build it as a team effort - share the work of putting it together.

Regards
Rob

@Bob,

I drew up some pieces of wire, one end fed and two center-fed with 180 degrees phase shift.
It looks to me that the phasing is correct if the center-feed is differential, but as usual I am open to all
positive criticism.

The gray background shows adjacent end-fed wires, resp. adjacent center-fed dipoles.
The phasing here also appears to me to be correct (series-aiding or in-phase).

I am also floating an idea about a concept of a center-fed peripheral coil being energized through a balanced transmission line from the center electronics.  Although I have indicated a magnetically- and electrostatically-shielded electronics area, it is possible that RE will go through this as easily as it goes through 1-yard thick steel.  Another possibility is to put the FET driver next to the coils while keeping the differential pre-driver in the center - - or put both driver and pre-driver at the coil

Regards, Earl

Quote from: Bob Boyce on August 13, 2007, 11:00:44 PM
@ Earl
If you center feed like that, will you not be injecting 2 out of phase energies? Coil wind direction on the toroid, as well as which end of that coil is being fed, are factors here. E-field propagation through a winding is not instantanious, so it does matter a little bit which end is driven. If you reverse the wind, or reverse the direction of feed, while maintaining the same direction of rotation as per hemisphere, you would have to invert your potentials and swap from a positive E-field bias / negative primary E-field pulses, to a negatve E-field bias / positive primary E-field pulses. Since free electrons tend to outnumber free holes, you should expect to see a corresponding drop in collectable energy.
Bob

Quote from: Earl on August 12, 2007, 07:18:26 AM
Hi Bob,
[snip]
I had another idea, which I will float to you.  Since an antenna can be fed anywhere along its length, left side, right right, top side, bottom side, corner, or anywhere in between - with no effect on its radiation performance (yes, you must match impedance) why not the same with a catalytic coil?  By feeding it in the middle, just like any dipole antenna, and using a FET driver with differential output you get TWICE the excitation voltage for essentially no increase in complexity or cost.

Your comments on attached drawing?

Regards, Earl