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In radio engineering and telecommunications, standing wave ratio (SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. Impedance mismatches result in standing waves along the transmission line, and SWR is defined as the ratio of the partial standing wave 's amplitude at an ...
RadioShack (formerly written as Radio Shack) is an American electronics retailer that was established in 1921 as an amateur radio mail-order business. Its original parent company, Radio Shack Corporation, was purchased by Tandy Corporation in 1962, shifting its focus from radio equipment to hobbyist electronic components sold in retail stores.
An SWR meter does not measure the actual impedance of a load (the resistance and reactance), but only the mismatch ratio. To measure the actual impedance requires an antenna analyzer or other similar RF measuring device. For accurate readings, the SWR meter itself must also match the line's impedance (typically 50 or 75 Ohms).
Cross-needle SWR meter on antenna tuner. It is a common misconception that a high standing wave ratio (SWR) per se causes loss. [3] A well-adjusted ATU feeding an antenna through a low-loss line may have only a small percentage of additional loss compared with an intrinsically matched antenna, even with a high SWR (4:1, for example). [21]
An amateur radio station may be operated under the call sign of the owner of the station (if they are near the controls), or the call sign of the person operating the station as a guest. In some countries, special call signs might be made available for clubs, and are frequently used at a club station established for use of the club's members.
The 10-meter band was allocated on a worldwide basis by the International Radiotelegraph Conference in Washington, DC, on 4 October 1927. [2] Its frequency allocation was then 28-30 MHz. A 300 kHz segment, from 29.700–30.000 MHz, was removed from the amateur radio allocation in 1947 by the International Radio Conference of Atlantic City. [3]
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By then computers were 35% of Radio Shack sales; the Model 100 was the world's best-selling notebook computer, while Tandy was the leading Unix vendor by volume, selling almost 40,000 units of the 68000-based, multiuser Tandy Model 16 with Xenix, [17] [23] and began selling all computers using the Tandy brand [24] because, an executive admitted ...