Products & Services
FM Telephone Bug
Apr 21 2010 12:17
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| 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.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.Parts:Part Total Qty. DescriptionR1 1 180 Ohm 1/4 W ResistorR2 1 12K 1/4 W ResistorC1 1 330pF CapacitorC2 1 12pF CapacitorC3 1 471pF CapacitorC4 1 22pF CapacitorQ1 1 2SA933 TransistorD1,D2,D3,D4 4 1SS119 Silicon DiodeD5 1 Red LEDS1 1 SPDT SwitchL1 1 Tuning CoilMISC 1 Wire, Circuit Board |
