1.5V FM transmitter circuit, 88-108MHz using transistors

These are four 1.5V FM transmitter circuit (low volt)  which use transistor and a few parts, without PCB but easy to build for output 88-108MHz or 90-100MHz, more circuits below

FM transmitter 88-108MHz using two transistors and 1.5V battery

This is also the 88-108 MHz FM transmitter circuit that use 1.5 volts battery power supply source and use two-transistors so easy to builds and small size circuits.

Figure 1 the schematic diagram

Figure 2 the components layout

The coil-L is 8 turns of 22 swg wire wound with a inside diameter air core of about 5mm. Then stretch the coil to width of 9 mm.
And to tap out to the antenna at 3 turns.

You can use all transistor number : 2SC461, 2SC784, 2SC785 instead of 2SC183 transistor and 2SC668, 2SC77 for 2SC185.

Then adjust the all current of this circuit by Stretching or shrinking the coils and adjustable TC (trimmer) to have the current approximately 3mA the frequency in 88-108 MHz range.

98-100MHz FM transmitters using one transistor and 1.5 volts battery

This is the small FM transmitters using one transistor and 1.5 volts battery as power supply, in 98MHz to 100 MHz FM frequency range.

The coil-L is 8 turns of 18 swg wire wound with a inside diameter air core of about 5mm. Then stretch the coil to width of 9 mm. The T1 use the OUT PUT transformer of small RF receiver. If can not find the transistor number 2SC838. Use 2SC458, 2SC461, 2SC784, 2SC1815 instead. Should adjust the total current of the circuit. Using finger kickoff to stretch or shrink coil. Measure the current with the meter to about 2-3 mA. Frequencies are in the range 98-100MHZ.

Note:
R1____10K_______0.25W Resistor
R2____100 ohms_____0.25W Resistor
T1____Transformer, Primary : 8 ohms, Secondary: 1.2K
SP1____8 ohms Speaker

FM transmitters, 90-100MHz using two transistors and low voltage

Today lets to see the simple FM transmitters,90-100MHz that use two transistors, apply power supply with 1.5V battery

The coil-L is 8.5 turns of 22 swg wire wound with a inside diameter air core of about 5mm. Then stretch the coil to width of 9 mm.

Figure 1 The schematic circuit diagram

To tap out to the antenna at 3 turns (from input voltage) then adjust the all current of this circuit by Stretching or shrinking the coils and adjustable TC (trimmer) to have the current approximately 3mA the frequency in 90-100 MHz range.

Figure 2 the components layout connection

If can not find the transistor number 2SC838. Use 2SC458, 2SC461, 2SC784, 2SC1815 instead. Should adjust the total current of the circuit. Using finger kickoff to stretch or shrink coil. Measure the current with the meter to about 2-3 mA. Frequencies are in the range 98-100MHZ.

Figure 3 Real connection the components

Note:
R2 = 3K___0.25W___Resisters
R3 = 15K___0.25W__Resisters
C3 = 0.001uF 50V Ceramic capacitor
Q1,Q2 = 2SC838 transistors___ 2SC458, 2SC461, 2SC784, 2SC1815 instead.

1.5V FM transmitter using a varicap diode and two transistors

This circuit is a 1.5V FM transistor circuit that use also two transistors like others circuit before. But this circuit is special that we use a varicap diode.

Figure 1 is a schematic diagram

– This circuit use the varicap diode number: SD111 or will use number 1S553, 1S85 instead.

– The both transistors will be used the 2SC838 or this circuit use many number : 2SC458, 2SC460, 2SC461, 2SC784, 2SC785, FCS9016, FCS9018.

-The coil-L is 7 turns of 22 swg wire wound with a inside diameter air core of about 5mm. Then stretch the coil to width of 12 mm.

Figure 2 the really components connection

– Adjust total current of this circuit we will stretch or shrink until the coil current of 2mA frequencies in the range of 90-100 MHz.

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Apichet Garaipoom

I love electronics. I have been learning about them through creating simple electronic circuits or small projects. And now I am also having my children do the same. Nevertheless, I hope you found the experiences we shared on this site useful and fulfilling.