Amplitude Modulation (AKA AM) was the first modulation type to impress audio on an RF carrier. Prior to this, information was transmitted via on/off keying of a continuous wave transmitter using Morse code or some equivalent. 1. Low level modulation. The modulation is developed in the first stage RF section, then amplified by subsequent stages to
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full power. Simple and easy to implement, especially for mobile transmitters and SSB installations. Disadvantages come from the need for linear amplification through all the stages requiring class A or AB amplifiers and does not reproduce wide band AM well. 2. Doherty modulation. William Doherty came up with an ingenious way to use a low level linear modulator with good to excellent efficiency. Under full carrier, no modulation conditions, the carrier tube is generating the RF carrier and the peak tube is mostly cut off (very little current). When modulation is applied, the peak tube then begins to conduct, the output of this tube is combined with the output of the carrier tube through a 90 ° LC network, which is the same as 1/4 wave length transmission line. The effect of this is to lower the output impedance, thus allowing the carrier tube to modulate 100 percent. 3. High level or plate modulation. The RF and Audio sections are developed separately with in the transmitter, then combined in the final stage of the transmitter. Older systems used a modulation transformer. Advantages are all the amplifiers can be run class C or greater, which reduced electrical consumption and power supply requirements. Much higher power levels are achievable with this design. These transmitters also reproduce wide band audio much better than low level modulated units. They are also extremely rugged. Disadvantages are the system requires...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
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The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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