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Spy Bug FM Transmitter
Posted on Monday, October 29, 2018   •   Category: FM Transmitters

Spy Bug FM Transmitter

This tiny 88-108Mhz FM transmitter bug measures just 10mm x 17mm in size and as you can see in the photos the biggest components are just the microphone and the battery. You can use a small microphone from an older cell phones, they are small in size and have an excellent sensitivity. For an effective power supply the 9V battery (Duracell) is excellent and allows several hours of battery life, but if you want to have a smaller size it is better to use 2 or 3 lithium cells like the 2032 used in PCs. The circuit works well from 3 to 12V, the maximum range is obtained with 12V and a piece of 40-60cm cable as an antenna.




Simple FM Radio Bug
Posted on Monday, September 10, 2018   •   Category: FM Transmitters

Simple FM Radio Bug

In the mid 1970s large numbers of small FM transmitters, operating in the FM radio broadcast band (88-108 MHz) appeared on the market. It started with a self-build kit from the Danish manufacturer Jostykit that allowed everyone to build a small FM transmitter for a few Euros. Such transmitters generally consist of a single transistor oscillator with a simple resonance circuit, sometimes with an extra transistor that is used as audio pre-amplifier. The image shows a few examples that were available in European electronics shops in the mid 1970s. The transmitter shown here was built in the mid-1970s and measures just 1 x 2 cm. When properly built, it may have a range of several kilometers.




1 Watt FM Transmitter
Posted on Wednesday, July 11, 2018   •   Category: FM Transmitters

1 Watt FM Transmitter

This is a simple, portable transmitter operating in the 88-108 MHz FM band. You may use it to run your own private neighborhood radio, just replacing the microphone capsule with a male audio jack connected to your pc or MP3 player. You may also use this as a spy transmitter, but be reasonable in that case. It's rated for 1 Watt, so you can listen to it even from a few kilometers, with a good antenna and not too much obstacles in the way.




PCM2707 USB DAC Soundcard
Posted on Tuesday, June 19, 2018   •   Category: Audio DAC

PCM2707 USB DAC Soundcard

The following is a simple USB DAC Soundcard. It uses PCM2707 that incorporates USB interface to communicate with the computer and audio DAC all in one chip.




Dual Adjustable Power Supply
Posted on Saturday, May 26, 2018   •   Category: Power Supplies

Dual Adjustable Power Supply

This project is a solution to power up most of devices or projects requiring dual (+/-) adjustable power supply. The circuit is based on LM317 positive and LM337 negative voltage regulators. LM317 series of adjustable 3 terminal regulator is capable of supplying in excess of 1.5A over a 1.2V to 30V DC output range, due to TO3 package of IC and large heat sink the power supply can handle maximum load current.




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