LONG RANGE FM TRANSMITTER ELECTRONIC DIAGRAM

LONG RANGE FM TRANSMITTER ELECTRONIC DIAGRAM

This circuit works optimally by adding RF amplifier and antenna. Here is the schematic diagram :

Parts list :

•     Diode D1 : BB109
•     Resistor R1 : 10k ohm
•     Resistor R2 : 100k ohm
•     Resistor R3 : 180k ohm
•     Resistor R4 : 4K7
•     Resistor R5 : 15k ohm
•     Resistor R6 : 68 ohm
•     Resistor R7 : 470 ohm
•     Resistor R8 : 39k ohm
•     Resistor R9 : 10 ohm
•     VR1 : 47k ohm
•     VR2 : 22 ohm
•     Capacitor C1-C3, C8 : 0.1 uF
•     Capacitor C4 : 4.7 pF
•     Capacitor C6 : 0.01 uF
•     Capacitor C7 : 5.6 nF
•     Capacitor C9 : 100 pF
•     Transistor T1: BF494
•     Transistor T2:2N3866
•     Trimmer VC1-VC2 : 50p
•     L1 : 4 round 20 cables SWG in plastic with 8mm diameter
•     L2 : 2 round 24 cables SWG
•     L3 : 7 round 24 cables SWG in plactic with 4mm diameter
•     L4 : 7 round 24 cables SWG in ferrid bead

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FM Transmitter Bug Circuit

Circuit Diagram 

Notes:

 This small transmitter uses a hartley type oscillator. Normally the capacitor in the tank circuit would connect at the base of the transistor, but at VHF the base emitter capacitance of the transistor acts as a short circuit, so in effect, it still is. The coil is four turns of 18swg wire wound around a quarter inch former. The aerial tap is about one and a half turns from the supply end. Audio sensitivity is very good when used with an ECM type microphone insert

  

Author: David, radio_david@yahoo.com
Source http://www.electronics-lab.com/

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FM remote Encoder Decoder

The
remote systems given here uses FM for the transmission. IC1 RF600E and
its associated components form the encoder circuit. Pins 1 to 4 forms
the switch inputs of IC1. When each push button switch is pressed a
corresponding code will be generated at the pin 6 which is the data
output pin. The encoded signal available at pin 6 is buffered using the
transistor Q1 and the fed to the input of a general purpose FM
transmitter module (M1). Such FM transmitter modules are very common in
the market now.

The decoder
system comprises of the IC2 RF600D and its associated components. Pins
17, 18, 1 and 2 are the digital data output pins of RF600D
corresponding to the input switches S1 to S4 of the encoder/transmitter
circuits. The digital data output pins 17,18,1 and 2 are asserted low
when the relevant inputs S1 to S4 on the IC2 RF600E are asserted. M2 is
a general purpose FM receiver module which receives the transmitted
code and feds it to the data input (pin 9) of the IC2. Switch S1 can be
used to select between latching and momentary digital output function.
In latching mode digital output pins (OP1 to OP4) are only asserted
for the corresponding transmit signal. In latching mode the output
state is changed on each corresponding transmit signal. The learn
switch S5 is used to enter the decoder IC in to the “learn mode”. Learn
operation using push button switch S5 is as follows. 1) Press and release the push button switch S5. 2) The status LED D2 will glow when S5 is pressed and will remain ON when S5 is released. 3) Operate the encoder/transmitter once. 4) The status LED D2 will become OFF. 5) Operate the encoder/transmitter again. 6) The status LED will start flashing. 7)
When the flashing of status LED stops, the encoder will be successfully
taught to the decoder and the transmitter/encoder will now operate the
receiver/decoder system. Up to seven encoder/transmitters can be
learnt to each RF600D.Pin 3 of IC2 is the transmitter low battery
indicator output and pin 11 is the serial data output.

Circuit diagram.


Notes.

• Assemble the circuit on a good quality PCB.
• The ICs can be operated from anything between 2V to 6.6V.
• Switches S1 to S5 are miniature push button switches.
• S6 can be a miniature two way switch.
• Transmit LED D1 will glow whenever the encoder is transmitting.
• The power supply must be properly regulated and ripple free.
• I recommend using batteries for powering the circuit.
• Go through the datasheets of RF600E and RF600D before attempting this circuit.

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