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It looks like a super regenerative receiver:
https://www.youtube.com/watch?v=qvpvn6T5PBQ&t=143s
Without the capacitor the circuit wouldn't oscillate. If you put the correct capacitor between the collector and emitter it will create a negative AC resistance on the collector.
With noise and negative resistance the LC tank will resonate, and the amplitude of the oscillation will increase.
In super regenerative receivers there is an other oscillation which is called "quenching". Quenching is when a slower circuit or the RF oscillator itself stops its own RF oscillation from time to time.
It creates a very good sensitivity for the receiver, because at the building up of a new RF oscillation period the received signal is added to the noise of the RF oscillator, and the building up is exponential!
So, for example if the received signal is an AM signal, and the momentary amplitude of this wave is a bit higher, the oscillation will build up much faster, and reaches higher power before the next stop.
It works with wideband FM signals too, in that case it works like a slope detector which is regenerative.
About how the quenching works you can read more from this paper, page 3:
https://www.smarterworld.de/fileadmin/media/whitepaper/files/MCA481wp_Low_costembedded_receiver.pdf[/QUOTE
OOh man thank you very much, but still i dont understand, capacitor betwen collector and emitter act like voltage divider? the capacitor he makes me very complicated circuits
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I agree that it is a super regen crappy FM tuner. It is too simple to be a real FM tuner.
where did you find me here man;-; rely this capacitor make me very complicated circuits, help me
"work" means what particularly?but i think this work also without capacitor between collector and emitter, i simulate
OOh man thank you very much, but still i dont understand, capacitor betwen collector and emitter act like voltage divider? the capacitor he makes me very complicated circuits
i read one articul over super regenarative oscillator, but i dont know wich value of capacitor c1 and c5 to put
The value of C1 determines its ability to "ground" the base of the transistor at radio frequencies.
The value of C5 determines the squegging frequency. For an FM tuner you do not want the squegging frequency too low to beat with the 19kHz pilot tone or beat with the 23kHz to 53kHz stereo sidebands or with the 67kHz storecast music sidebands. But you want the value of C5 to bypass R3 at the radio frequency.
Are you making a tuner for the FM broadcast band at around 100MHz?
Did you try it with the capacitor values shown on the schematic you found and the similar schematic I found?