# Time and frequency users' manual, Volume 13

George Kamas
Department of Commerce, National Bureau of Standards, Institute for Basic Standards, Time and Frequency Division, 1977 - Frequencies of oscillating systems - 210 pages

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Page 22 - That the functions of the bureau shall consist in the custody of the standards; the comparison of the standards used in scientific investigations, engineering, manufacturing, commerce, and educational institutions with the standards adopted or recognized by the Government; the construction, when necessary, of standards, their multiples and subdivisions; the testing and calibration of standard measuring apparatus; the solution of problems which arise in connection with standards; the determination...
Page 158 - The second is the duration of 9, 192, 631, 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium- 133 atom (13th CGPM, 1967).
Page 96 - E — Theory El. A direct (unidirectional) current is one which does not reverse its direction of flow. An alternating current is one which reverses its direction of flow periodically. Two reversals, one in each direction, constitute a cycle. The number of cycles per unit of time is the frequency. Thus, 60 cycles per second means 120 reversals per second. E-2. The transformer for supplying ac power to the rectifier consists of a primary winding or coil and one secondary winding. The secondary winding...
Page 26 - ... frequency differences. Terms like high, low, and offset should be avoided. Since the algebra speaks for itself, it should be used with a minimum of additional terms. 3. 1 EXPRESSING FREQUENCY DIFFERENCE (IN HERTZ, kHz, MHz, ETC.) The actual frequency of a source is indicated by the lowercase letter, f. (Refer to the glossary at the end of this book for a further explanation and definition.) A subscript can be used to identify the particular frequency source; eg, fc for an oscillator designated...
Page 118 - In figure 6.16, the most significant digit of the minutes set is (1 x 40) + (0 x 20) + (0 x 10) = 40; the least significant digit of that set is (0 x 8) + (0 x 4) + (1 x 2) •*• (0 x 1) = 2. Thus, at the beginning of the frame, UTC was precisely 42 minutes past the hour. The sets for hours and days reveal further that it is the 18th hour of the 258th day of the year. The UT1 correction is -0.7 second, so at the beginning of the frame the correct time on the UT1 scale was 258 days, 18 hours, 41...
Page 117 - WWVB time code is generated by shifting the power of the 60-kHz carrier. The carrier power is reduced 10 dB at the beginning of each second and restored to full power 200 milliseconds later for a binary zero, 500 milliseconds later for a binary one, and 800 milliseconds later for a reference marker or position identifier. Certain groups of pulses are encoded to represent decimal numbers which identify the minute, hour, and day of year. The binary-to-decimal weighting scheme is 8-4-2-1 with the most...
Page xii - In addition to staff members of the Time and Frequency Division of the National Bureau of Standards, material and comments have been supplied by other government agencies, manufacturers, and individuals.
Page 175 - Q value of 10 . Atomic collisions as well as the simultaneous action of the light and the microwave signals on the same atom cause frequency shifts of the order of 10~9. These frequency shifts depend strongly on the composition, temperature, and pressure of the buffer gas and on the intensity of the light. As a result, rubidium gas cells vary in their resonance frequency by as much as 10"^, depending on the particular setting of the frequency shifting parameters during manufacture.
Page 90 - BCD group is derived by multiplying each binary digit times the weight factor of its respective column and then adding the four products together. For instance, the binary sequence 1010 in the 1-2-4-8 scheme means (1 x 1) + (0 x 2) + (1 x 4) + (0 x 8) = 1 + 0 + 4 + 0 = 5, as shown in the table. If fewer than nine decimal digits are needed, one or more of the binary columns may be omitted. In the standard IRIG-H code, a binary 0 pulse consists of exactly 20 cycles of 100-Hz amplitude modulation (200...