P1 act as condenser microphone volume level. For FM, coil will be small. Use thin gauge enamel magnet wire. the diameter of coil will be a couple mm: use ink tube from pen to form, and try 8-12 turns. Small inductance coils make for much guess work.
Components List
R1=220K
R2=4.7K
R3,R4=10K
R5=100ohm C1,C2=4.7uF Electrolytic
C3,C4=1nF
C5=2-15pF
C6=3.3pF Q1=BC547C
Q2=2N2219A
P1=25K
MIC=Electret Condenser Type
