VTTC – The Beginning

This will be my second coil, when I finish building it !

The vacuum tube coil uses a very large Russian radio transmitter valve in place of the spark gap in the standard coil. It runs as a self controlled oscillator, continually charging and discharging the tank capacitor into the primary coil. They use three coils, the primary coil, the feedback coil which controls the rate of oscillation and the secondary coil. They run at lower voltages and much higher frequencies than spark gap coils and produce shorter, spiky discharges from a much smaller topload.

+++Primary Coil+++

25 Turns 2.5mm copper cable wound on a 15cm former.

+++Secondary Coil+++

1000 turns of 0.315mm enammelled copper wire on a
68mm pvc former.

+++Feedback Coil+++

20 Turns thin wire on the same former as the primary coil,
mounted 1cm below,

+++Power Supply+++

2.1kV 1300W Microwave oven transformer
12v 12A transformer for Vacuum Tube Heater Supply
Standard line filter at transformer supply, earthed to RF ground
68uF Power factor correction
275v MOV accross supply

+++Tank Capacitor+++

1880pF 20kV Ceramic capacitor rated at 60kVAr

+++Control Box+++

Standard line filter at input, earthed to supply ground
275v MOV across supply outputs
Variac power control
Input ‘Live’ and ‘Ready to fire’ warning lamps
Output voltage and current meters
Key operated safety switch
Two simultaneous press-to-fire buttons and a long extension lead !!

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