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single frequency TRF vacuum tube receiver design

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neazoi

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Hello I design a simple receiver for dcf77 using ECC86 tubes and ferrite loop antenna
Here is my design of the amplifiers.
Can you spot any errors?
 

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betwixt

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You probably want to put some negative volts on the control grids, either by really applying negative or by putting resistors in the cathodes. The negative has to be relative to the cathode so you can achieve it by making the cathode a few volts positive while keeping the grids at ground potential.

I would suggest you are extremely careful with screening when dealing with such high gain and you might need a 'neutralizing' circuit on each stage (a kind of negative feedback) to keep it stable. When you put a tuned circuit in the grid and in the anode, the internal capacitance between electrodes can be enough to make it oscillate. A four stage oscillator would be a nightmare to debug !


Brian.
 
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