Simple audio transmitter
This transmitter showed good quality of transmitted music, so I recommend starting with this circuit.
As practice has shown, an assembled generator on one transistor cannot stand in one place, without an additional cascade, the frequency constantly drops when you raise your hand or apply voltage. I used the transmitter within one room, so I didn’t, they’ll use an additional cascade. As you can see, this generator uses two transistors, which allows you to keep the frequency stable. The varicap was excluded from the scheme; in my opinion, it did not play a significant role.
Supply voltage 6 volts. Current consumption is 0.2 ampere. Range 88-107 MHz.
The frequency goes down when it supplies voltages up to 3.7 volts, so I recommend including a 5-volt voltage stabilizer “7805” in the circuit; such stabilizers are found on FM transmitters and on the DVD board. I installed a diode to increase the voltage.
Light-emitting diode also helps the generator remain more stable. This generator does not react to foreign objects or when you raise your hand, unless of course we hold it by the antenna.The power supply uses a transformer for a voltage of 9 v, ampere 0.2. Diodes IN4007, you can of course IN4004, IN4001. Electrolyte at 3300 uF. And it is imperative to bypass each diode with a 10n capacitor, otherwise it will produce nasty noise.
You also need to connect a 10n capacitor between the case and the plus.
The length of the antenna is about 35 cm, the range to a mobile phone with obstacles is 60 m. Also, you don’t need to connect a helical antenna, it worsens the efficiency, range, broadband, and if you connect it to a socket, a hum will appear from the alternating voltage. Those who used such antennas were deeply mistaken. GOOD LUCK TO ALL RADIO AMATEURS AND RADIO AMATEURS.
As practice has shown, an assembled generator on one transistor cannot stand in one place, without an additional cascade, the frequency constantly drops when you raise your hand or apply voltage. I used the transmitter within one room, so I didn’t, they’ll use an additional cascade. As you can see, this generator uses two transistors, which allows you to keep the frequency stable. The varicap was excluded from the scheme; in my opinion, it did not play a significant role.
Supply voltage 6 volts. Current consumption is 0.2 ampere. Range 88-107 MHz.
The frequency goes down when it supplies voltages up to 3.7 volts, so I recommend including a 5-volt voltage stabilizer “7805” in the circuit; such stabilizers are found on FM transmitters and on the DVD board. I installed a diode to increase the voltage.
Light-emitting diode also helps the generator remain more stable. This generator does not react to foreign objects or when you raise your hand, unless of course we hold it by the antenna.The power supply uses a transformer for a voltage of 9 v, ampere 0.2. Diodes IN4007, you can of course IN4004, IN4001. Electrolyte at 3300 uF. And it is imperative to bypass each diode with a 10n capacitor, otherwise it will produce nasty noise.
You also need to connect a 10n capacitor between the case and the plus.
The length of the antenna is about 35 cm, the range to a mobile phone with obstacles is 60 m. Also, you don’t need to connect a helical antenna, it worsens the efficiency, range, broadband, and if you connect it to a socket, a hum will appear from the alternating voltage. Those who used such antennas were deeply mistaken. GOOD LUCK TO ALL RADIO AMATEURS AND RADIO AMATEURS.
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