Radio receiver

The inherent noise fluctuations of a radio receiver usually determine the weakest signal strength that can be measured with a radio telescope. The statistical nature of noise radiation is such that statistical fluctuations are proportional to the noise power itself. Furthermore, the average of N independent measurements of the noise power is Va times more accurate than a single measurement. Noting that a single independent measurement can be made in the minimum time interval /dv, we see that the maximum number of independent measurements that can be made in time t vs, tdv. Thus, the sensitivity equation for an ideal receiver is given by 

Earth-based radio observations of the planets have limitations which affect certain types of measurements. These limitations include (1) the inability to obtain spatial resolution on scales of a few meters or less, (2) restrictions on the viewing geometry of the planets, (3) limitations set by the opaqueness and variability of the terrestrial atmosphere, (4) the intrinsic faintness of the radio emissions from planetary bodies, and (5) interference from manmade radio noise. The opacity of the terrestrial atmosphere varies with frequency. The atmosphere is opaque at frequencies lower than about 5 MHz due to the terrestrial ionosphere. Attenuation due to the atmospheric gases, water vapor, and oxygen affects the centimeter, millimeter, and submillimeter bands, but observations are possible 

In the future, we expect to see many more radio astronomy spacecraft experiments. Spacecraft experiments will allow the submillimeter spectral range to be observed without hindrance from the terrestrial atmosphere. Planetary spectroscopy in the submillimeter spectral range is expected to reveal new information about the upper atmospheres of the planets. The ESA ROSETTA spacecraft 

---

In 1916, Alexanderson made another important contribution to radio broadcasting when he unveiled his tuned radio receiver, which allowed for selective tuning. It quickly became an integral part of radio broadcasting. 

The main fields of application for this battery chemistry include portable TVs, radio receivers, lamps, flashlights, electric shavers, barrier lightning, instruments, batteries for portable rechargers, emergency power supplies, small refrigerators, power sources for tourists, hunters, geologists, shepherds and so on. Parameters of some batteries, assembled from the modules, are summarized in Table 4. 

Radiations outside the ultraviolet, visible and infrared regions cannot be detected by conventional photoelectric devices. X-rays and y-rays are detected by gas ionization, solid-state ionization, or scintillation effects in crystals. Non-dispersive scintillation or solid-state detectors combine the functions of monochromator and detector by generating signals which are proportional in size to the energy of the incident radiation. These signals are converted into electrical pulses of directly proportional sizes and thence processed to produce a spectrum. For radiowaves and microwaves, the radiation is essentially monochromatic, and detection is by a radio receiver tuned to the source frequency or by a crystal detector. 

As the protons fall back to the lower energy state, the same radio frequency that was absorbed is emitted. This can be measured with a radio receiver. This phenomenon is known as proton nuclear magnetic resonance ( H NMR). 

If vibration is applied both through the cantilever tip (at frequency heterodyne detection. The AFM tip detects the oscillating force at the difference frequency cot — cos, very much like a heterodyne radio receiver. This technique is known as heterodyne force microscopy (HFM Cuberes et al. 2000). Once again, the tip-surface force non-linearity plays a critical role. The low-frequency beating oscillation carries information on the phase of the original high-frequency oscillations. 

A further impetus for commercial battery development came with the introduction of domestic radio receivers in the 1920s, and an equivalent growth has been seen over the last 30 years with the development of microelectronics-based equipment. Today, it is estimated that annual battery production totals 8-15 units per head of population throughout the developed countries of the world. 

SEMICONDUCTORS. Materials and devices known as semiconductors have been the backbone of the electronics industry for many years. Semiconductors did not enter the industry in a major way, however, until several years after the vacuum tube (valve) had been well established. In terms of perspective, it is interesting to note that at least one. semiconductor device predated the vacuum tube in the early days of radio communication. This was the then familiar galena crystal and accompanying whisker used in early crystal set radio receivers. 

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... 

Filters based on this principle made from PZT ceramic have been widely used in the intermediate frequency stages of FM radio receivers. More stable units suitable for telecommunication filters are made from single-crystal LiTa03 and quartz. 

This can be compared to answering the question How is a stereo system made with the words By plugging a set of speakers into an amplifier, and adding a CD player, radio receiver, and tape deck. Either Darwinian theory can account for the assembly of the speakers and amplifier, or it can t. 

The spectrometer is a radio receiver, and we change the frequency to tune in each nucleus at its characteristic frequency, just like the stations on your car radio. Because the resonant frequency is proportional to the external magnetic field strength, all of the resonant frequencies above would be increased by the same factor with a stronger magnetic field. The relative sensitivity is a direct result of the strength of the nuclear magnet, and the effective sensitivity is further reduced for those nuclei that occur at low natural abundance. For example, 13C at natural abundance is 5700 times less sensitive (1/(0.011 x 0.016)) than H when both factors are taken into consideration. 

If R is small, then Q0 is large. Equation (9.2.51) also applies to radio receivers, whose "tank" circuit which can be analyzed as a single RLC circuit. 

We then detect the energy given out when the nuclei fall back down to the lower energy level using what is basically a sophisticated radio receiver... 

Radio-bridge — A bridge circuit similar to the - audio-bridge except the signal source produces frequencies in the radio frequency range (e.g., 50 kHz-50 MHz) and a radio receiver (or even an oscilloscope) is used to determine the condition of null. 

While performing their regular tasks, Dunmore, together with Lowell, experimented at the laboratory in devising apparatus for operating a radio receiving set by alternating current with the hum incident thereto eliminated. The invention was completed on Dec. 10, 1921. Before its completion no instructions were received from and no conversations relative to the invention were held by these employees with the head of the radio section or with any superior. 

Born in St. Louis, Missouri on October 9, 1899, Ralph Shriner was the oldest of the two children of George B. Shriner and Edith Barnett Shriner. His father worked as an agent for the railroad for some years. Ralph and sister, Ruth, attended public schools in St. Louis. During the summers, Ralph worked on his Uncle Al s farm in Cuba, Missouri, in the Ozarks, southwest of St. Louis. His uncle also owned the Ford Model T dealership, and one of Ralph s jobs was to go to the freight yard with his cousin Jim, assemble the cars, and drive them to the sales yard. Thus, Ralph learned to drive at the tender age of 12. Uncle Al also became the owner of the local telephone company, after it went bankrupt, and Ralph and his cousin Jim became the line repairboys, learning how to fix the phones, climb the poles, and maintain the wires. In his teens, Ralph built his own radio receiver and transmitter and became a ham radio operator. He was active in the Boy Scouts, became an Eagle Scout, and later served as a scoutmaster. 

Walter Haus Schottky (1886-1976) received his doctorate in physics under Max Planck from the Humboldt University in Berlin in 1912. Although his thesis was on the special theory of relativity, Schottky spent his life s work in the area of semiconductor physics. He alternated between industrial and academic positions in Germany for several years. He was with Siemens AG until 1919 and the University of Wurzburg from 1920 to 1923. From 1923 to 1927, Schottky was professor of theoretical physics at the University of Rostock. He rejoined Siemens in 1927, where he finished out his career. Schottky s inventions include the ribbon microphone, the superheterodyne radio receiver, and the tetrode vacuum tube. In 1929, he published Thermodynamik, a book on the thermodynamics of solids. Schottky and Wagner studied the statistical thermodynamics of point defect formation. The cation/anion vacancy pair in ionic solids is named the Schottky defect. In 1938, he produced a barrier layer theory to explain the rectifying behavior of metal-semiconductor contacts. Metal-semiconductor diodes are now called Schottky barrier diodes. 

---