Ok, so the main circuit is a super regenerative receiver.
The variable capacitor to tune it is maybe OK.
What frequency is this receiver intended to work at?
The sketch of the variable capacitor infers something out of a broadcast receiver, be aware that if the receiver is intended for VHF, the capacitor will be too large if it came out of a long/medium wave radio.
But, the "varicap diode"!
What you have sketched looks like another varable capacitor, which is fine if you are trying to put a small capacitor in parallel with a large capacitor to give a "fine tune" or "band spread" tuning control.
But a varicap diode it is not.
Varicap diodes look much like othe diodes, a small cylinder with a wire out of each end, (OK there are variations on this, but lets keep it simple for now).
You could use a varicap diode in the position shown, but the circuit would be a bit more complex than shown in your diagram.
What are you trying to achieve?
Jim GM3ZMA