[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
VTTC - optimal primary coil
Original poster: "Herwig Roscher by way of Terry Fritz <twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de>
I am running a VTTC, driven by a power tetrode. Plate voltage is 10
kV filtered DC. Secondary coil is wound onto a 4" form.
In order to find the "best" tank circuit configuration, I wound several
8" primary coils:
70 ÁH, 116 ÁH, 127 ÁH, 640 ÁH and 1100ÁH
After having tuned the system carefully in each configuration, I
found the results of the first 3 coils to be lousy. With the 2 other
coils I gained the same 17" discharges and I am assuming, that
this is, what I could expect.
To my surprise it was not possible, to find the "optimal" coil
inductance. With the help of list members I came to the following
If the impedance of the tank circuit was not extremly low, its
influence on the output power is low. The impedance, seen by the
plate, mainly is the reflected impedance of the load. The
impedance of the tank circuit itself becomes infinity at its natural
Different tank capacitances (necessary to keep the system in tune)
did not affect the performance either (bang size).
Varying the coupling between primary and secondary coil from 0"
to 2.3" (secondary above primary) had no visible influence neither
on the length of the discharges nor on the volume of the plasma
ball. Length of the 1100 ÁH coil is 4".
While tetrodes have higher plate resistances than triodes when
operated in A-mode, plate resistance is not an important factor
when operated in C-mode. Here the tube is driven into plate current
saturation and acting as a switch.
Any comments/critics are very welcome.