A Radio Yardstick

Radio Record, Volume III, Issue 46, 30 May 1930, Page 26

A Radio Yardstick

FUNCTIONING with an exactness of better than one- part in 1,000,000, a radio yardstick has been designed by the American Bureau of Standards . for measuring the frequencies or wayelengths of the 600 broadcasting stations, 16.000 amateur stations, and other radio transmitters existing in America. It will detect broadcasting stations that are wabbling, or straying from their assigned wavelength, and it means improved reception to the estimated 10.000,000 listeners in the United States. This new radio yardstick consists of four miniature transmitters. The heart of the instrument is the quartz erystal or mineral, which acts as a governor of.the transmitters. Heretofore these slabs of minerals have been cut in dise or other shapes, but here they take the form of rings. as Tests have shown that ring-shaped | crystals are least subject to variations of temperature and therefore are more constant and precise as governors of radio wavelengths or frequencies. The erystal governors are aa protected from moisture and e

variations by inclosing them in a:"ell jar, at a pressure slightly below atmospheric, Also they are covered by a shell of aluminium. with a wall one inch thick. The wall holds a heater and a thermostat element.