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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Well, as some of you know, i build Steve Wards mini sstc. I decided that i was sick of having corona problems on the antenna, antenna arcs (happened once, for unknown reason because i forgot), instability, oscillations stopping or going crazy do to having a grounded object too close to the topload, so that the antenna would not pick anything up, and worrying about anything touching the antenna. So, i decided to switch to CT feedback.
Thanks to Tribologist for the CT. I used a CT made for the minibrute, with 2 or 3 windings (i am not sure what it would be considered) of high voltage wire from a flyback. I connected the primary windings, one to earth ground, and one to base of the secondary. After this, i took the secondary (this could be anywhere from 30-60 windings, probably more or less is possible) and connected on end to the ground of the driver, and the other side to a .1uf film capacitor and 10kohm 1/4 watt resistor in series, going straight to the 74hc14. Make sure your clamping diodes are good enough, as they will definitely be needed.
Turn ratio is something to be experimented with. More primary windings would be suggested, as this ensures good coupling/power transfer. As i learned on my last thread, do not leave the CT unloaded, as it can arcs over internally, and it will heat up badly. Mine did not arc over, but it did heat. I will include a video in my sstc project thread, so keep your eyes peeled. If i remember, i will let you know on this thread.
What the CT improved, was all of the above mentioned problems with the antenna. The spark length stayed about the same, but all in all, i would say it is much better than the antenna. there is just much less to worry about. Also, i can touch the topload with a grounded object, and the arcs do not decrease in thickness, and the oscillations are very stable.
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