Metal Detectors
... some applications it may be desirable to drive a small loudspeaker. Where this is the case the output at P3 could be connected to a small power amplifier. Because the design of the circuit is very simple it will tend to suffer from problems such as frequency drift. This is not always a serious probl ...
... some applications it may be desirable to drive a small loudspeaker. Where this is the case the output at P3 could be connected to a small power amplifier. Because the design of the circuit is very simple it will tend to suffer from problems such as frequency drift. This is not always a serious probl ...
Radio Station Setup and Electrical Principles
... Acts as open circuit at low frequency Acts as short circuit at high frequency ...
... Acts as open circuit at low frequency Acts as short circuit at high frequency ...
Manual - Qi Xuan
... C. Wiring and usage of power meter Power meter (wattmeter) is a moving coil instrument, whose current coil is connected to the load in series and the voltage coil is connected to the load in parallel. The correct wiring of power meter: one terminal of the current/voltage coil is marked by “*”. When ...
... C. Wiring and usage of power meter Power meter (wattmeter) is a moving coil instrument, whose current coil is connected to the load in series and the voltage coil is connected to the load in parallel. The correct wiring of power meter: one terminal of the current/voltage coil is marked by “*”. When ...
Inductor Lab (RL and LC circuits)
... 1. Simulate the circuit below. It is known as an LR circuit. L is the symbol for an inductor and R the symbol for a resistor. The mathematics used to describe this circuit is similar to that for the RC circuits we studied earlier. The voltage across an inductor is proportional to the change in curre ...
... 1. Simulate the circuit below. It is known as an LR circuit. L is the symbol for an inductor and R the symbol for a resistor. The mathematics used to describe this circuit is similar to that for the RC circuits we studied earlier. The voltage across an inductor is proportional to the change in curre ...
Document
... From Faraday’s law: a time varying flux through a circuit will induce an EMF in the circuit. If the circuit consists only of a loop of wire with one resistor, with resistance R, a current ...
... From Faraday’s law: a time varying flux through a circuit will induce an EMF in the circuit. If the circuit consists only of a loop of wire with one resistor, with resistance R, a current ...
Crystal radio
A crystal radio receiver, also called a crystal set or cat's whisker receiver, is a very simple radio receiver, popular in the early days of radio. It needs no other power source but that received solely from the power of radio waves received by a wire antenna. It gets its name from its most important component, known as a crystal detector, originally made from a piece of crystalline mineral such as galena. This component is now called a diode.Crystal radios are the simplest type of radio receiver and can be made with a few inexpensive parts, such as a wire for an antenna, a coil of copper wire for adjustment, a capacitor, a crystal detector, and earphones. They are distinct from ordinary radios as they are passive receivers, while other radios use a separate source of electric power such as a battery or the mains power to amplify the weak radio signal so as to make it louder. Thus, crystal sets produce rather weak sound and must be listened to with sensitive earphones, and can only receive stations within a limited range.The rectifying property of crystals was discovered in 1874 by Karl Ferdinand Braun, and crystal detectors were developed and applied to radio receivers in 1904 by Jagadish Chandra Bose, G. W. Pickard and others.Crystal radios were the first widely used type of radio receiver, and the main type used during the wireless telegraphy era. Sold and homemade by the millions, the inexpensive and reliable crystal radio was a major driving force in the introduction of radio to the public, contributing to the development of radio as an entertainment medium around 1920.After about 1920, crystal sets were superseded by the first amplifying receivers, which used vacuum tubes (Audions), and became obsolete for commercial use. They, however, continued to be built by hobbyists, youth groups, and the Boy Scouts as a way of learning about the technology of radio. Today they are still sold as educational devices, and there are groups of enthusiasts devoted to their construction who hold competitions comparing the performance of their home-built designs.Crystal radios receive amplitude modulated (AM) signals, and can be designed to receive almost any radio frequency band, but most receive the AM broadcast band. A few receive shortwave bands, but strong signals are required. The first crystal sets received wireless telegraphy signals broadcast by spark-gap transmitters at frequencies as low as 20 kHz.