470-580 MHz UHF TV Transmitter

TV transmitter circuit is working on the UHF channell, 470-580 MHz frequency channel 21-34. This transmitter can radiate as far as 30-100 meters by using a cable 10-20 cm.

TV transmitter requires supplies voltage of 9-15 Volt. However, you can also use a 9v batteries.

This is an important thing to remember for building of the tv ransmitter circuit is that the dimensions of coil size to match the frequency of the desired work. The value of the spindle is making coil as follows:
L1, L2 = 3 Turns, diam. 3mm, 0.5mm wire
L3 = 2 Turns, diam. 3 mm, 0.5 mm wire


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VHF Video Transmitter for Camera

This is a simple video transmitter that can radiate as far as 50 meters. This video transmitter can be used with the camera as a source. You can view them on VHF channel analog TV. Supply voltage to the transmitter can use 9V battery.

Transistor components that are used for a video transmitter is BC548 or you can use another type of transistor BF199. Meanwhile, other passive components used SMD type. For winding coil L1 is 5 Turns 8 mm in diameter and use wire AWG 0.3-0.5 mm.

Once you up the circuit this video transmitter, antenna use as a cable along the 50 cm. To determine the frequency of work, turn the trimmer capacitor 22 pf accordance with the frequency that you want.

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Audio Limiter/Compressor for Electret Desk Microphones

This electronic circuit is audio limiter compressor specifically designed to use with very low-cost electret desk microphones. Overcomes the heavy attack/decay problems with diode rectifier VOGAD circuits.

A TL074 IC was used with a dual supply of +/-5v Note the lack of rectifier diodes in the feedback loop, instead the circuit uses high gain BC848(smd BC108) This uses the full wave rectifier effect to give a non-linear compression level avoiding the worst of the 'pumping' normally noticed with discrete diodes. R38 sets the compression level/bias point to suit the hfe of the selected transistor. Note Q2 is a P channel Junction FET eg J176.

Source: http://www.g8ajn.tv/projects.htm

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