FM Transmitter
Here is the schematic, PC board example, and parts position for a low controlled FM transmitter. The scope of the transmitter when running at 9V speaks the truth 300 feet. Running it from 12V expands the reach to around 400 feet. This transmitter ought not be utilized as a room or phone bug.
Schematic
| C1 | 1 | 0.001uf Disc Capacitor | |
| C2 | 1 | 5.6pf Disc Capacitor | |
| C3,C4 | 2 | 10uf Electrolytic Capacitor | |
| C5 | 1 | 3-18pf Adjustable Cap | |
| R1 | 1 | 270 Ohm 1/8W Resistor | 270 Ohm 1/4W Resistor |
| R2,R5,R6 | 3 | 4.7k 1/8W Resistor | 4.7K 1/4W Resistor |
| R3 | 1 | 10k 1/8W Resistor | 10K 1/4W Resistor |
| R4 | 1 | 100k 1/8W Resistor | 100K 1/4W Resistor |
| Q1, Q2 | 2 | 2N2222A NPN Transistor | 2N3904, NTE123A |
| L1, L2 | 2 | 5 Turn Air Core Coil | |
| MIC | 1 | Electret Microphone | |
| MISC | 1 | 9V Battery Snap, PC Board, Wire For Antenna |
L1 and L2 are 5 turns of 28 AWG lacquer covered magnet wire twisted with an inside distance across of around 4mm. Within a ballpoint pen functions admirably (the plastic tube that holds the ink). Uproot the structure in the wake of twisting then introduce the loop on the circuit board, being mindful so as not to curve it.
C5 is utilized for tuning. This transmitter works on the typical telecast frequencies (88-108MHz).
Q1 and Q2 can likewise be 2N3904 or something comparable.
You can utilize 1/4 W resistors mounted vertically rather than 1/8 W resistors.
You may need to sidestep the battery with a .01uf capacitor.
A radio wire may not be needed for operation.
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