This small, easy installation allowing you to listen to on the FM band (88-108 MHz) while what is happening around him in a very clear and precise.
FM Transmitter Operation:
The assembly is built based on an oscillator-type COLPITTS that modulates an electret microphone.
The transistor T1 (BC550) serves as both amplifier and oscillator signal BF HF.
The transmission frequency is adjustable through C4 (2-22 pF), which allows to calibrate the transmitter to the desired location on the FM band.
Fig.1 Schematic electronic assembly
Fig.2 PCB across a given copper side mounting
MOUNTING
solder the resistors, capacitors (except the adjustment will be mounted with the latest electret microphone), the self and the transistor.
* L1 consists of six turns of enamelled copper wire wound on 7/10ème mm of the tail of a forest of 4mm.
The choke L1 must be made with special care under penalty of malfunctioning assembly. (Unable to calibrate in the FM band).
Fig.3 Diagram of installation of components
The volume of the assembly of your choice can be installed in a case containing the battery or be hidden in a small package. The switch is mounted either on the front of the housing or within such a small package.
LIST OF INGREDIENTS
R1 = 15 kOhm
R2 = 100 ohms
R3 = 100 ohms
C1 = 100 nF milfeuil
C2 = 220 pF ceramic
C3 = 220 pF ceramic
C4 = 2-22 pF adjustable
C5 = 4.7 pF ceramic
T1 = BC 550 NPN
L1 = Self (see text)
M1 = Micro electret
S1 = SPDT
START
1) Set an FM receiver on an unoccupied frequency.
2) Turn the transmitter on.
3) Adjust the capacitor C4 in order to capture the receiver the signal from the transmitter.
4) After setting approached refine playing on the set C4 and the FM receiver to get the best sound quality possible.
(The setting of the receiver can be pushed in order to increase the sensitivity to listen to the soft sounds).
The antenna was carried out on the circuit board, which allows to avoid disturbing the oscillator.
We noted a consumption of 6.5 mA and our test allowed us to determine a range for about a hundred meters.
FM Transmitter Operation:
The assembly is built based on an oscillator-type COLPITTS that modulates an electret microphone.
The transistor T1 (BC550) serves as both amplifier and oscillator signal BF HF.
The transmission frequency is adjustable through C4 (2-22 pF), which allows to calibrate the transmitter to the desired location on the FM band.
Fig.2 PCB across a given copper side mounting
MOUNTING
solder the resistors, capacitors (except the adjustment will be mounted with the latest electret microphone), the self and the transistor.
* L1 consists of six turns of enamelled copper wire wound on 7/10ème mm of the tail of a forest of 4mm.
The choke L1 must be made with special care under penalty of malfunctioning assembly. (Unable to calibrate in the FM band).
Fig.3 Diagram of installation of components
The volume of the assembly of your choice can be installed in a case containing the battery or be hidden in a small package. The switch is mounted either on the front of the housing or within such a small package.
LIST OF INGREDIENTS
R1 = 15 kOhm
R2 = 100 ohms
R3 = 100 ohms
C1 = 100 nF milfeuil
C2 = 220 pF ceramic
C3 = 220 pF ceramic
C4 = 2-22 pF adjustable
C5 = 4.7 pF ceramic
T1 = BC 550 NPN
L1 = Self (see text)
M1 = Micro electret
S1 = SPDT
START
1) Set an FM receiver on an unoccupied frequency.
2) Turn the transmitter on.
3) Adjust the capacitor C4 in order to capture the receiver the signal from the transmitter.
4) After setting approached refine playing on the set C4 and the FM receiver to get the best sound quality possible.
(The setting of the receiver can be pushed in order to increase the sensitivity to listen to the soft sounds).
The antenna was carried out on the circuit board, which allows to avoid disturbing the oscillator.
We noted a consumption of 6.5 mA and our test allowed us to determine a range for about a hundred meters.
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