Video Wireless Transmitter

To design and build a wireless transmitter that works over the FM frequency and allows the transfer of a video/audio signal over a certain distance to an FM tuner.  Click on this image to enlarge   In this fast-paced world, there is little time for inconveniences and a greater need for portability and adaptability. The idea for an Audio/Video transmitter stems from this need. There may have been times when you've wanted to hook up your VCR from one room to another television set in another room. But that would have entailed that you first unhook all kinds of wires and plugs from the primary TV set; carry the VCR to the next TV...

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Tube Li Amplifier

The unit is powered directly from the 120 volt AC line, with no power transformers. Filaments are wired in series, with the total adding up to 117 volts (35 + 35 + 35 + 12). The 35W4 forms a half-wave rectifier, which is filtered by a three-stage RC network. The B+ for the output stage plates and screens are taken from the second capacitor, and the B+ for the preamp and phase inverter from the third capacitor in the filter.  The input signal to the amplifier is applied directly to the volume control pot, from whence it passes through a variable high-pass filter (the "Treble" control). When the wiper is set to minimum, response is approximately...

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Rain Detector Using Transistor

  This rain detector will give you a heads-up the instant it starts to rain, hopefully giving you time to close windows and bring in possessions.  click on this image to enlarge The battery-powered circuit draws virtually no current when the sensor is dry and the current consumption is low when the buzzer is activated so a couple of AA cells will last a long time. Alternately, a molded power supply with a simple voltage regulator to drop the voltage to 3 volts could be used. The circuit is basically a handy flasher circuit that operates well on only 3 volts using ordinary silicon transistors. When the circuit is triggered, the...

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