Simple FM Transmitter
The following is a design for a very simple fm transmitter. It
also can be used as a bug or wireless microphone.
Construction Info
Using the following values this transmitter can be used on
frequncies between 30 and 110 MHz. The mic is a magnetic mic for all
three version. Although Electric mics may be more useful as a bug.
To build for the 30-40 MHz range:
L1 - .445uH Inductor with ferrite core. 8.5 turn, MC120 case TOKO coil.
C1 - 15-20 pF trimmer capacitor
C2 - 10-15 pF trimmer capacitor
ant.- 38" wire
To build for the 40-50MHz range:
L1 - .358uH Inductor with ferrite core. 7.5 turn, MC120 case TOKO coil.
C1 - 15-20 pF trimmer capacitor
C2 - 10-15 pF trimmer capacitor
ant.- 37" wire
To build for the 90-100 MHz range:
L1 - .317uH Inductor with ferrite core. 6.5 turn, MC120 case TOKO coil.
C1 - 5.6 pF capacitor
C2 - 3.3 pF capacitor
ant.- 20" wire
Make sure that C1 and C2 are NPO type capacitors so the device will
have some frequency stability. Other frequencie ranges can be obtained
by changing the values of L1, C1 and C2.