Help on Barkhausen Kurz tube oscillator

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neazoi

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Hello,
I have build this oscillator and it works ok https://commons.wikimedia.org/wiki/File:Barkhausen_Kurz_PC88.svg

I have made a small modification (attached). I basically included two RFC chokes on the filament pins to block any RF passing through the filaments to the PSU.
In old phillips books I have seen that these chokes always exist there.

Is my thought about these RFCs added right?
 

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  • myOSC.bmp
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FvM said:
Now the oscillator is missing the RF ground.
Click to expand...

No part of the tube is connected to the RF ground, as far as I understand. The RF ground (coaxial cable ground) is connected directly to the chassis and the chassis is connected to the 0V point, not the tube cathode directly.

See the phillips book oscillator, they use chokes at both filament pins. This is another type of oscillator though.
 

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Last edited:

The question is how you extract the RF. The latest link has an inductive coupler, it doesn't need a ground. Your circuit however does.
 
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    neazoi

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FvM said:
The question is how you extract the RF. The latest link has an inductive coupler, it doesn't need a ground. Your circuit however does.
Click to expand...

Ah, we cross-posted.
No part of the tube is connected to the RF ground, as far as I understand. The RF ground (coaxial cable ground) should be connected directly to the chassis and the chassis is connected to the 0V point, not to the tube cathode directly.

I may be wrong though. Maybe I should leave L4 out and use just L3? But then will L3 do any good at all??

Also, would a DC blocking capacitor help at Fo, to prevent DC from reaching any potential post amplifiers? Should I try 1pf or so for 1-3GHz?
 
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