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Registered Member #1642
Joined: Sun Aug 17 2008, 11:36PM
Location: Black Canyon City
Posts: 96
Thought you guys might get a kick out of this; It's a high level (plate modulated) VTTC powered by a pair of 304tl's @ Jim @ has done a fabulous job constructing the web page which now includes Schematics and Wiring Diagrams of the actual 304TL modulator! The output blows the doors off of "standard" MOSFET designs, which are normally FM modulated. Although the parts I used may be somewhat hard to find these days, I don't see any reason one can't use a car stereo bass amplifier to do the same thing using MOSFET design and a large filament transformer (6.3 volts or 12.6 volt to 120 volts AC) to do the same thing. I know of someone who has just done this, and his results are incredible. "Talk Power" is where it's at using plate (or buss) modulation. Simple rules are that the modulator needs to have about 60% of the total power input to the RF deck; so for a 500 watt tesla coil, you would need about 300 watts of audio. Peak to Peak envelope power causes the sparks to really "jump" on hard hitting audio; truly fascinating.
Registered Member #4603
Joined: Wed Apr 25 2012, 07:33PM
Location: Austria
Posts: 159
Thats a nice setup. 60% of the RF power for audio just to modulate a grid!? That would explain the low audio output of my coils... I will change that...
Registered Member #1642
Joined: Sun Aug 17 2008, 11:36PM
Location: Black Canyon City
Posts: 96
FYI: It's PLATE MODULATION, not grid. The modulator xfmr goes between the B+ source and the plate of the coil...relatively simple. Same principle as the "CQW" stuff, you're varying the input to the plate with audio from a series connected xfmr.
Registered Member #4603
Joined: Wed Apr 25 2012, 07:33PM
Location: Austria
Posts: 159
Ahh okay. Sorry. That explains the high power of the modulator... "THIS is the modulation transformer, professionally rewound on a 2.2 kVA core by the original builder" I was wondering what that thing costs
But why plate modulation? Whats the advantage towards grid modulation?
Registered Member #1642
Joined: Sun Aug 17 2008, 11:36PM
Location: Black Canyon City
Posts: 96
The Peak Envelope Power (PEP) available from plate modulation is 4X the nominal input power compared to grid modulation, I think that's why the flames "jump" considerably higher than normal FM or grid modulated coils.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Well it is really cool, no doubt about it... but I think that screen or suppresor modulation (with a suitable tube) would require about 1/3 of the components and total weight
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Plate Modulated Tesla Coil (VTTC)
