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Registered Member #333
Joined: Mon Mar 20 2006, 06:02PM
Location: Czech Republic
Posts: 45
I also tried an experiment with bottom feedback VTTC on 3 of my existing secondaries but the result vas very poor. It always started to oscillate but it can olny glow small glowing tube or do up to 1mm sparks to ground object. I can notice that bigger secondary resulted to worse performance. But it would be expectable that on lower frequencies the bottom feeded TC resonator would have too high impedance compared to tube - less efective power transfer.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
I forgot to post here :P. I tried this with a large secondary with 350khz resonant freq, and the results where somewhat good. Almost as long of sparks as regular primary/feedback coil without tuning :P. I used an 811A.
Also i tried this on a quite small secondary with about 8.2mhz resonant frequency power by an 833C without voltage doubler (fullwave rectified actually and smoothed) The sparks where about an inch long, and of course where extremely hot. The plate would get red in only 10-20 seconds though!
Registered Member #333
Joined: Mon Mar 20 2006, 06:02PM
Location: Czech Republic
Posts: 45
Arcstarter wrote ...
I tried this with a large secondary with 350khz resonant freq, and the results where somewhat good.
Wow, so it seems that I made some mistake somewhere (but I don't know what because of this circuit is extreme simply :). The only difference was that I used different triode Telefunker RV239 because LD50 was lying on the table at work. But it's not problem to bring more power (GU-81M + MOT with doubler :). I tested on 3 of my secondaries with f0: 330kHz, 2,15MHz and 2,5MHz.
Could you please tell me some deteils about your setup? - what kind of feedback you used? grid antenna or feedback coil? how many turns and where located FB coil? - what power supply did you used for the tube and what value of RF-stop choke? - what spark length you reached? on such secondary it shouldn't be problem to get ~30cm with MOT power - schematics? ;)
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Small dirty VTTC from scratch done in one hour
