Another new trick for FM launch

At present, most of the transmitters that are widely introduced use capacitive three-point oscillation circuits, and their frequency stability is not high. In addition, many beginners are limited by the theory and practical experience of high-frequency circuits. too much. Although the crystal oscillator circuit is stable, the circuit is relatively complicated and the frequency deviation is small, which cannot meet the requirements for music. Here I introduce a highly stable transmitter that can meet the requirements of amateurs.
Find a VCD radio frequency modulator. This modulator is a separate shield box on many VCDs. The input terminals are + 5V power supply, video, audio, and shell grounding. Because the general modulator works in the 8-10 channel, the frequency is higher, and the actual production should be properly handled: find the oscillation coil in the modulator and replace it with a coil with a larger inductance to reduce the frequency. The author used a medium lmm enameled wire, which was formed by winding 7 turns on a + 5mm rod, with a frequency of 107.5MHz. In order to improve the effect, the video can be partially disconnected to reduce interference. Then replace the audio part capacitors with tantalum capacitors or other high-quality capacitors, and an excellent transmitter will come to an end.
Because the circuit adopts Dingkobitz oscillation, its stability is much improved compared to the capacitor three-point type, coupled with its almost drip-proof shield, the frequency is quite stable. No matter touching the antenna with your hand or touching other metals, you don't feel the frequency run away from the radio. The only drawback is that the output power is small. But adding an appropriate power amplifier, I believe it will not be difficult for fans, and then add a beautiful shell to it, you can enjoy the radio-level music.

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Another new trick of FM launch-high stability transmitter

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2.5MM Wire To Board Connectors

2.5MM Wire To Board Connectors.

Connectors can be classified into three basic types: line to line, line to board and board to board. These three types of connections are not entirely different. There are two reasons for this type of overlap. First of all, the design of the same connector only needs to be redefined after slightly changing the connection mode, that is to say, it becomes a new design scheme that can be applied to another type of connection mode; secondly, a cable can be installed with a line to line connector at one end and a line to board connector at the other end during assembly, for example, the appearance of class 5 I / O connector is the most common one See for example. If we avoid the fuzziness of this kind of connection, it will provide an effective basis for connector classification.

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