Circular of the Bureau of Standards no. 573:

Abstract

The National Bureau of Standards is engaged in fundamental and applied research in physics, chemistry, mathematics, and engineering. Projects are conducted in fifteen fields: electricity and electronics, optics and metrology, heat and power, atomic and radiation physics, chemistry, mechanics, organic and fibrous materials, metalliu'gy, mineral products, building technology, applied mathematics, data processing sys¬ tems, cryogenic engineering, radio propagation, and radio standards. The Bureau has custody of the national standards of measurement and conducts research leading to the improvement of scientific and engineering standards and of techniques and methods of measurement. Testing methods and instruments are developed; physical constants and properties of materials are determined; and technical processes are investigated.

The Development of Loran-C navigation and timing

“…However, an increase in surface refractive index will also increase the lapse rate (rate of decrease in refractive index with height) and this will tend to decrease the propagation time of the LF signal. A possible means for resolving the effects could be related to the fact that a surface refractive index change does not affect the signal amplitude, but a change in lapse rate does affect the amplitude of the signal One instance where the groundwave theory, as worked out by Johler, Kellar, and Walters (1956), may relate to the temporal effects is: the change in phase predicted for a given change in lapse rate is greater for a low-conductivity path than for a high-conductivity path.…”

“…The subscripts m and s identify the master and slave signals. This equation is based on the theory given in NBS Circular 573 (Johler, et al, 1956), but the a corrections have been added to allow additional path parameters that are not considered in the Circular.…”

“…The effect of the dielectric con stant is calculable but is of only very minor practical importance at low frequencies. The phase of the low-frequency groundwave has been evaluated by Johler et al (1956) in NBS Circular 573. This publication has served as the basis for virtually all Loran-C phase calculations even though only a smooth, homogeneous earth is considered.…”

“…The propagation times were computed in accordance with NBS Circular 573 (Johler et al 1956), "Phase of the low radio frequency ground wave". Secondary corrections for paths of mixed conductivity were computed by a method given by Millington (Millington and Isted, 1950).…”

“…Three sets of time-difference curves based on NBS Circular 573 (Johler et al, 1956) were computed for each of the crossings (conductivities of 0.0005, 0.001 and 0.005 mhos/m) were used. The measured values, plotted to the best scale, were super imposed on the computed curves for the best overall fit.…”