Amplifier radio

In 1919, he made history with yet another of his inventions when his multiple-tuned antenna, antistatic receiver, and magnetic amplifier were used to transmit the first two-way radio conversation. This great event took place 900 miles out to sea, between the Trans-Atlantic Marconi Company station at New Brunswick and the steamship George Washington, with President Woodrow Wilson on board as a witness. 

The invention of the germanium transistor in 1947 [I, 2] marked the birth of modem microelectronics, a revolution that has profoundly influenced our current way of life. This early device was actually a bipolar transistor, a structure that is mainly used nowadays in amplifiers. However, logical circuits, and particularly microprocessors, preferentially use field-effect transistors (FETs), the concept of which was first proposed by Lilicnficld in 1930 [3], but was not used as a practical application until 1960 [4]. In a FET, the current flowing between two electrodes is controlled by the voltage applied to a third electrode. This operating mode recalls that of the vacuum triode, which was the building block of earlier radio and TV sets, and of the first electronic computers. 

Power supply, x-ray tube, constant-potential, 245, 246 full-wave, 244, 245 half-wave, 244, 245 radio frequency, 149 three-phase, 246 Pre-amplifier, use, 60, 243 Precision, 266... 

Optical parametric oscillator (OPO, see 20) is the real equivalent to the radio frequency shifter however OPO can be replaced by a simple addition of a local oscillator (e.g. laser) through a beam splitter. Multiplication takes place at the level of detectors. For sake of S5mimetry, detectors can be placed at both output of the beam splitter, the intermediate frequency is then the output of the differential amplifier. 

Now today, we have found about a hundred different masers in space and some lasers. The difference between a maser and a laser is of course only in the wavelength. But there are some astronomical systems where infrared is getting amplified. Now as has been pointed out, amplification in interstellar space doesn t involve resonances, but it does involve stimulated emission. You know, somebody could have seen these interstellar masers in the radio regions of the spectrum many years ago. Anybody who used the radio technology of 1936, and looked up into the sky, could have detected this water frequency. They didn t bother to look, but it was there all the time. So now we know, lasers have been there for billions of years. Masers have been there billions of years. So that s another way we might have discovered them, but we didn t. Now I emphasize this to indicate that we need to search, we mustn t be too confined by what we think is going to work, we ve got to explore. 

In 1948 William Bradford Shockley (1910-1989), who is considered the inventor of the transistor, and his associates at Bell Research Laboratories, Walter Houser Brattain (1902-1987) and John Bardeen (1908-1991), discovered that a crystal of germanium could act as a semiconductor of electricity. This unique property of germanium indicated to them that it could be used as both a rectifier and an amplifier to replace the old glass vacuum tubes in radios. Their friend John Robinson Pierce (1910-2002) gave this new solid-state device the name transistor, since the device had to overcome some resistance when a current of electricity passed through it. Shockley, Brattain, and Bardeen all shared the 1956 Nobel Prize in Physics. 

Barium titanate has many important commercial apphcations. It has both ferroelectric and piezoelectric properties. Also, it has a very high dielectric constant (about 1,000 times that of water). The compound has five crystalline modifications, each of which is stable over a particular temperature range. Ceramic bodies of barium titanate find wide applications in dielectric amplifiers, magnetic amplifiers, and capacitors. These storage devices are used in digital calculators, radio and television sets, ultrasonic apparatus, crystal microphone and telephone, sonar equipment, and many other electronic devices. 

Apparatus. All electrical resistances were measured with an electrolytic conductivity bridge (Leeds and Northrup model 4666) which was constructed according to specifications set forth by Jones (28) and described by Dike (29). The audio-frequency source was a General Radio Co. type 1311-A audio oscillator used with the frequency regulated at 1000 Hz and the output at about 5 V. The detector circuit consisted of a high-gain low-noise tuned amplifier and null detector (General Radio Co. type 1232-A) and an oscilloscope (Heathkit model O-ll) ... 

So little current flows across a glass electrode that it was not practical when discovered in 1906. One of the first people to use a vacuum tube amplifier to measure pH with a glass electrode was an undergraduate, W. H. Wright at the University of Illinois in 1928, who knew about electronics from amateur radio. Arnold Beckman at Caltech invented a portable, rugged, vacuum tube pH meter In 1935, which revolutionized chemical instrumentation.16... 

In the conventional NMR experiment, a radio-frequency field is applied continuously to a sample in a magnetic field. The radio-frequency power must be kept low to avoid saturation. An NMR spectrum is obtained by sweeping the rf field through the range of Larmor frequencies of the observed nucleus. The nuclear induction current (Section 1.8.1) is amplified and recorded as a function of frequency. This method, which yields the frequency domain spectrum f(ai), is known as the steady-state absorption or continuous wave (CW) NMR spectroscopy [1-3]. 

Fiber optic systems are more economical than their alternatives—copper wire, radio relay, and satellite. The regeneration of signals sent on copper cables is necessitated at several mile intervals, whereas tile distance on optical fibers can be. over a thousand miles by using optical amplifiers approximately every 50 miles. 

In terms of antique radio technology, this radiometer with an RF amplifier leading to a square-law device is a tuned RF receiver which was the state-of-the art in 1929. The modem superheterodyne circuit for radio receivers with ampflication and filtering at an intermediate frequency (IF) was used by the COBE DMR, but the primary advantage of a superheterodyne receiver over a... 

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