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Registered Member #1412
Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278
I always want to build VTTCs but don't have time to build one.I now decided to build it in the upcoming vacation and finally found all the parts.
I found two 8298/6146 (datasheet:
I had read this already but this coil seems to be different from other coil.If I hope I can learn something that can help me build the next VTTC,what circuit should I build? I also have read steve's page.
Some people says that if higher frequency is used,RF loose will increase.Is this true?
I planned to build a 500KHZ secondary using 6CM PVC pipe. is this ok?
I planned to use this tube to build my next VTTC.Any suggestion?
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
ummm... i'm not an expert on vttcs, but i don't think you can use that tube. vttcs use a vacuum triode, and usually have 5 wires. 2 filament, anode, cathode, and grid.
iv never built a vttc, so i couldn't say what your target resonant frequency is, or anything about rf losses, sorry
i would recommend( if your not sure about those tubes) to get a pair of 811a's or a similar triode. Steve Ward has a good design for those: VTTC 1 - Dual 811A
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
ben123324 wrote ...
ummm... i'm not an expert on vttcs, but i don't think you can use that tube. vttcs use a vacuum triode, and usually have 5 wires. 2 filament, anode, cathode, and grid.
.
The data sheet says it is a power triode. Have you looked at the schematic, Ben? (maybe the water cooling fittings confused you?)
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
Both those tubes should work fine for a fairly small VTTC. You wouldn't be able to use an MOT connected to main for either of these tubes as it supplies too much voltage but if you have a variac, it shouldn't be a problem. Even though the 6383 has a higher anode power dissipation, it requires water cooling which might be more work than it's worth. This tube can go up to microwave freqs so you may want to save it or something.
Higher freqs means there are more RF losses due to dielectric heating of the secondary and also at higher freqs, the skin effect may start to become significant and so you'd have higher resistive losses. RF losses are something to pay attention to when trying to improve your coil. If you just want breakout, pretty much anything is fine.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
@Myke, I think the data sheet said the 6383 will run at frequencies as low as 10 kHz. While the water cooling does create some extra problems, doesn't this mean it would be suitable?
(I'm new to VT technology, but I'm trying to learn. I'd be tempted to use the 6383 because it can dissipate more power, even though I'd need to 'rig up' a 12 volt bilge pump (£5 off Ebay if you don't already have a few knocking about) or something to cool it. Is there any other reason why it would be unsuitable?)
Registered Member #1412
Joined: Thu Mar 27 2008, 04:07PM
Location: Taipei Taiwan
Posts: 278
I bought a pair of 811 because more information is available on the internet.
I now get 8~10cm spark using MOT without level shift or voltage doubler.But plate turn orange after 10 seconds of running.
I also don't know what kind of capacitor to use.I originally use some red epoxy coated capacitor but I later found that ERO capacitors work better.Can I use CDE capacitors?(I cannot afford doorknob capacitor)
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Need help with my very first VTTC
