Note, see this page for comparative data on this coil as a 2 or 3 coil system.
I got to thinking about what else could be done with DRSSTC technology. I got to thinking about how much the coil arcs to the primary and strike rail, and how much of a nuisance it is. I then began thinking about the magnifier and the fact that it can *efficiently* move the output arcs some distance from the driver, no more risk there now! There is of course more complications with setting up a magnifier since you have more coils, but I think I can handle it. I did some quick pspice simulations of a DRSSTC magnifier to get some feeling for tuning. Pspice suggested I would need to tune the whole thing slightly higher than the original resonant frequency of my old secondary. Well, this just isn't so in reality. I'm tuned a full turn lower than usual and could use some more! This is just a test after all, so my next try will have more turns available.
So I quickly threw together a test with my DRSSTC-3 and an old secondary I had on hand to be used as the "Driver". The driver coil (or secondary) is 4.5"x10" of 24awg magnet wire topped off with a 8"x1.5" toroid to prevent corona (I actually don't think its a problem at this power level). The "resonator" (tertiary or 3rd coil) is the DRSSTC's original secondary, 4.5"x11" of 30awg winding with a 12"x2" toroid on top. Below are some pictures of the setup, not too exciting, just thrown together for now as a test (I have plans for something larger in the future). While I'm not technically the first to build a DRSSTC magnifier, I'm probably one of the first to get desirable results from it. By simply increasing the coupling between my driver coil and primary to the point of flash over and tuning the primary as low as it can go, I have achieved about 36" sparks so far which is about where it maxed out as a 2-coil system. So far the only thing I have gained is the extra isolation (the output sparks are well away from the driver). There might be more performance to be had if I can further increase K as well as get the proper tuning needed (higher K demands the primary operate at a lower frequency), I'm not advocating that magnifiers are more efficient, but there might be some benefit (though I have yet to see it).
And finally, pictures! There was a lot of sunlight getting into my room, so the sparks are a bit washed out. Good enough for now... sparks are sparks! The toroid center is 24" above the ground plane, the metal target is 31" away. Some of the strikes down to the clip lead are a good 35" or so.
I took some time to refine the original lash-up. Here are some pictures of the finalized construction of this magnifier. Note how I can revert to a 2-coil system in a matter of minutes!
The lower level electronics.
My trusty CT, calibrated against a pearson wideband CT.
New primary setup. Taller PVC support in the center allows for greater control of coupling.
I built a nice stand and a new toroid for the resonator, new toroid is 3"x16".