This project is a simple 2-transistor VHF power amplifier, with about 16dB gain, and requires no tuning or alignment procedures. Wideband techniques have been used in the design and the circuit is equipped with a "lowpass" filter to ensure good output spectral purity. The project has been designed for assembly on a single-sided printed circuit board. The circuit is specifically designed to amplify the output of 7mW to 10mW WBFM transmitters (wide band) to a final level of 250mW to 300mW.
Posted on Saturday, September 11, 2010 • Category: Headphone Amplifiers
The small AF amplifier Suitable for laptops and MP3 players. IT may be powered from the PC (Game or USB) or AC adapter.The basis of the amplifier is an integrated circuit TDA2822M. With this circuit you can build an amplifier with output up to 2x 1 W. This high power circuit is only able to supply at peak times, when excited, would be permanently unable to work. Involvement of the amplifier is to figure 1. The input signal passes through frequency-dependent volume control on the divider. Frequency-dependent divider produces frequencies around 100 Hz, with a positive influence on the subjective sound quality when using small speakers. IO is the involvement of manufacturers' recommendations. The amplifier output can connect speakers with an impedance of 8 ohms (or greater), or headphones. IO supply voltage can be in the range of 1,8 to 15 V. The low supply voltage power amplifier is very small, at high supply voltage and load speakers with low impedance circuit may be a little overheated. With 8 ohm speakers are suitable voltage in the range of 6-9 V. I used to supply voltage 5 V, which are derived from the game port. Voltage of 5 V can be obtained even from the keyboard connector, PS / 2 port and USB. A better option is a network adapter, there are no problems with earth loops.
Posted on Saturday, September 11, 2010 • Category: FM Radio / Receivers
The communications between commercial aircraft and the ground can be interesting, amusing and sometimes even disturbing. However radios that receive the approximately 220MHz to 400MHz band commonly used for aircraft (both military and commercial) are not easily found. And scanners can be complicated, large and expensive. With an easy to build circuit such as this one, everyone can enjoy listening in on these conversations.
Posted on Friday, September 3, 2010 • Category: FM Transmitters
5W PLL Stereo FM Transmitter features PLL synthesized drift free operation with high quality BH1415 chip. 5W RF output power is achieved with 2SC1971 6W transistor in the output stage. Front panel digital control comes with LED display and case is made high quality aluminum. The board features EMI filtering on audio and power inputs and comes with Microphone and Audio inputs. Once transmitter is turned on it starts broadcasting with previously selected frequency. Overall this 5W PLL Stereo FM Transmitter provides professional broadcast audio quality and rivals commercial broadcasts.
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