FM Telephone Bug
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FM Telephone Bug
Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range
is about 200 feet. It is extremely easy to build and is therefore a
good, useful beginner project.
Schematic
PARTS
R1 = 180 Ohm 1/4 W Resistor
R2 = 12K 1/4 W Resistor
C1 = 330pF Capacitor
C2 = 12pF Capacitor
C3 = 471pF Capacitor
C4 = 22pF Capacitor
Q1 = 2SA933 Transistor
D1, D2, D3, D4 = 1SS119 Silicon Diode
D5 = Red LED
S1 = SPDT Switch
L1 = Tuning Coil
Notes
1. L1 is 7 turns of 22 AWG wire wound on a 9/64 drill bit. You may need to experiment with the number of turns.
2. By stretching and compressing the coils of L1, you can change the frequency of the transmitter. The min frequency is about 88 Mhz, while
the max frequency is around 94 Mhz.
3. The green wire from the phone line goes to IN1. The red wire from the phone line goes to IN2. The green wire from OUT1 goes to the phone(s), as well as the red
wire from OUT2.
4. The antenna is a piece of thin (22 AWG) wire about 5 inches long.
5. All capacitors are rated for 250V or greater.
6. The transmitter is powered by the phone line and is on only when the phone is in use. S1 can be used to turn the transmitter off if it is not
needed.
7. If you have problems with the LED burning out, then add a 300 ohm 1/4W resistor in series with it.
is about 200 feet. It is extremely easy to build and is therefore a
good, useful beginner project.
Schematic
PARTS
R1 = 180 Ohm 1/4 W Resistor
R2 = 12K 1/4 W Resistor
C1 = 330pF Capacitor
C2 = 12pF Capacitor
C3 = 471pF Capacitor
C4 = 22pF Capacitor
Q1 = 2SA933 Transistor
D1, D2, D3, D4 = 1SS119 Silicon Diode
D5 = Red LED
S1 = SPDT Switch
L1 = Tuning Coil
Notes
1. L1 is 7 turns of 22 AWG wire wound on a 9/64 drill bit. You may need to experiment with the number of turns.
2. By stretching and compressing the coils of L1, you can change the frequency of the transmitter. The min frequency is about 88 Mhz, while
the max frequency is around 94 Mhz.
3. The green wire from the phone line goes to IN1. The red wire from the phone line goes to IN2. The green wire from OUT1 goes to the phone(s), as well as the red
wire from OUT2.
4. The antenna is a piece of thin (22 AWG) wire about 5 inches long.
5. All capacitors are rated for 250V or greater.
6. The transmitter is powered by the phone line and is on only when the phone is in use. S1 can be used to turn the transmitter off if it is not
needed.
7. If you have problems with the LED burning out, then add a 300 ohm 1/4W resistor in series with it.
Hertz- Admin
- Posts : 1822
Join date : 2010-08-12
Age : 43
Location : Cagayan De Oro City
Re: FM Telephone Bug
sir tanong lng po meroon ka bang circuit 2kilomers na fm transmeter jan.ung dito lng sa atin na bibili ung mga transistor
jhon martinez- AAA Battery
- Posts : 1
Join date : 2012-01-24
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