Galena. Lead ore deposit[edit] Galena deposits are found worldwide in various environments.[3] Noted deposits include those at Freiberg, Saxony;[1] Cornwall, The Mendips, Somerset, Derbyshire, and Cumberland, England; the Madan, Smolyan Province, Rhodope Mountains, Bulgaria; the Sullivan Mine of British Columbia; Broken Hill, Australia and the ancient mines of Sardinia.
Galena also occurs at Mount Hermon in Northern Israel. In the United States, it occurs most notably in the Mississippi Valley type deposits of the Lead Belt in southeastern Missouri,[1] and in the Driftless Area of Illinois, Iowa and Wisconsin. The economic importance of galena to the early history of the Driftless Area was so great that one of the towns in the region was named Galena, Illinois. Parabolic microphone. Parabolic microphone used at an American college football game.
A parabolic microphone is a microphone that uses a parabolic reflector to collect and focus sound waves onto a receiver, in much the same way that a parabolic antenna (e.g., satellite dish) does with radio waves. Typical uses of this microphone, which has unusually focused front sensitivity and can pick up sounds from many metres away, include nature recording, field audio for sports broadcasting, eavesdropping (for example, espionage), and law enforcement. Parabolic microphones are generally not used for standard recording applications because they tend to have poor low-frequency response as a side effect of their design. This is a direct result of the physical laws that govern sound waves.
Parabolas only focus waves with a wavelength much smaller than the diameter of the parabola. Sound-powered telephone. A sound-powered telephone is a communication device that allows users to talk to each other with the use of a handset, similar to a conventional telephone, but without the use of external power.
This technology has been used for at least six decades for both routine and emergency communication on ships to allow communication between key locations on a vessel even if power, including batteries, is no longer available.[1] A sound-powered phone circuit can have two or more stations on the same circuit. The circuit is always live, thus a user simply begins speaking rather than dialing another station. Sound-powered telephones are not normally connected to a telephone exchange. Operation[edit] The microphone transducer converts sound pressure from a user's voice into a minute electrical current, which is then converted back to sound by a transducer at the other end. Usage[edit] SkyWaves Home Page. Xtalset101. Copywrite 1997, 1998 - Alan R.
Klase - All rights reserved. Welcome to Crystal Set Design 102. It is assumed that you've already completed the 101 level course elsewhere, and know, at least, something about electronics in general and crystal radios in particular. If not, hit the books. The stuff in your public library will get you started. My approach is to build crystal radios out of quality vintage radio parts. In a crystal set, all the audio power that arrives at your ear drum came from the distant transmitter. SINGLE TUNED SETS These improvements result in a better than average crystal radio. THE TWO-CIRCUIT RECEIVER There are several way to implement variable coupling in the two-circuit set.
The primary inductance will want to have a maximum value of about 500 uH to reach down to 530 KHz. Crystal radio. Boy listening to a modern crystal radio The rectifying property of crystals was discovered in 1874 by Karl Ferdinand Braun,[5][6][7] and crystal detectors were developed and applied to radio receivers in 1904 by Jagadish Chandra Bose,[8][9] G.
W. Pickard[10] and others. Crystal radios were the first widely used type of radio receiver,[11] and the main type used during the wireless telegraphy era.[12] 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.[13] After about 1920, crystal sets were superseded by the first amplifying receivers, which used vacuum tubes (Audions), and became obsolete for commercial use.[11] However they continued to be built by hobbyists, youth groups and the Boy Scouts[14] as a way of learning about the technology of radio.
History[edit] Schakelingen - Kristal radio. KRISTALRADIO. Www.kristalradio.nl - Algemeen. Hoe Is De Radio Onstaan? Beperkte chronologische volgorde van markante gebeurtenissen in verband met de historische telecommunicatietechniek Geboorte van William van Gilbert. in 1600 beschreef Gilbert in zijn boek “Die magnete", diverse lichamen, die na wrijving, lichte voorwerpen kunnen aantrekken.Hij geeft aan deze aantrekkingskracht de naam elektriciteit.
Dit woord is afgeleid van het Grieks elektron, dat amber betekent. Hij bouwt ook de eerste elektroscoop, waarmee elektrische verschijnselen kunnen worden waargenomen. Hij overlijdt in 1603. Otto von Guericke maakt de eerste elektriseermachine. 1650 : Comenius voorspelt: er zal een tijd komen, waardoor het mogelijk zal worden met vrienden te spreken op een afstand van meer dan 1000 mijl. Halley bestudeert het aardmagnetisme, en tekent de eerste kaart met declinaties. De Engelsman John Gray ontdekt dat er geleiders en niet geleiders zijn voor statische elektriciteit. De geboorte van de Fransman Charles Augustin de Coulomb. Van Musschenbroek.