Help me understand a scheme

[alfedorov]

Hi everybodyes!

I inherited the device. This is an iron box. Inside there is a vacuum tube, a choke, a coil, a capacitor, high-voltage power.

At the top of the box there is a copper needle, it is isolated from the box by a fluoroplastic plate. When the device is turned on, the copper needle lights up.

I drew a rough outline.

On the box there are two handles. One changes the resistance, the other changes capacitors.

I put the dipstick on the box from the oscilloscope and looked at the signal.
Packs of high-frequency pulses with a frequency of 25 MHz are coming.
The bursts of pulses are interrupted at a frequency of several kHz. The interruption time is regulated by two handles on the box.

The discharge shape is regulated by handles and depends on the frequency of the interruption time.

Can you please tell me how this scheme works?

[Mads Barnkob]

There is no doubt that you have a tube oscillator, but there is one thing that makes me wonder.

The grid leak circuit, the two adjustable knobs for capacitance and resistance, they will adjust how many electrons are allowed to pass from cathode to anode, so negative charges on the grid will block the electrons, but as it is connected to the enclosure, this is either floating, grounded or picking up some induced charges from the discharge into the enclosure...

I only built the class C Armstrong oscillator that has a dedicated feedback circuit to drive it. http://kaizerpowerelectronics.dk/tesla-coils/kaizer-vttc-i/

[alfedorov]

I learned that this scheme is called a "super-regenerator". The coil to which it is connected is a "basefeed"  https://highvoltageforum.net/index.php?topic=177.0

But more my knowledge is not enough.

PS. But positive charges on the grid do not block the electrons, but rather facilitate their passage.

[Mads Barnkob]

Oops what a blunder It is true, electrons are blocked with a negative charge on the grid.

I still think that it uses the enclosure as feedback antenna for driving the grid at the basefed circuit resonance.

[AndreiRS]

I just don't know, but for some reason I thought about microwave ovens which have on side of the HV transformer connected to it. Maybe that helps your theory in some way.