Establishment of new facilities for WWVL and WWVB

Abstract

A brief report of the new facilities for standard radio broadcast stations WWVL and WWVB is appropriate here for two reasons. First, the organizers of the Symposium on the Ionospheric Propagation of VLF Radio Waves, to which this issue is devoted, graciously allocated a session of the Symposium for the dedication of the new stations. characteristics and accuracy of these broadcasts arc of clear interest as a tool in VLF and LF propagfLtion r esearch. Secondly, in this first issue of the new journal, R adio Science, it is pleasant to stress an example where radio propagation activities and radio standards activities combine so nicely to fall under the broader term, radio science. dedication of the e facilities to the public ser vice was made by A. V. Astin, Director of the National Bureau of Standards. An address, The Presen t Status of National Standard s for the Basic PhysicnJ Quanti ties, by R. D. Huntoon was part of the dedication sessio n. T echnical papers descrip ti \'e of the transmitLer design , the an tenna design, the frequency and Lime con trol system, and the staLion usefulness in proyiding standard frequencies and times were presented, and are listed by Litle elsewhere in this issue. Both stations are located near Ft. Collins, Colo. Station WliVVI.1 broadcasts at 20 kc/s with a design objecti\'e of 50 kw deli\Tered to the antenna and 1.5 kw radiated. Station vYWVB broadcasts at 60 kc/s with a design objective of 50 kw delivered to the antenna and 10 kw radiated, Frequency of both is normally held to within 2 parts in lOll of the United States Frequency Standard. Deviations from the stated frequency are published for users interested in the highest possible accuracy, Frequency control is realized by a 100 mile round trip servo loop between Ft, Collins and Boulder. carrier phases as recei\red at Boulder are compared with the phase of the working atomic frequency standard. Error signals, from both the 20 kc/s and 60 kc/s transmissions, modulate a 50 lI[c/s FM telemetering transmitter at Boulder. These signals are recovered at Ft, Collins and applied to a servo-motor driven resolver at the input of each transmitter. A significant feature is that long term phase coherence of the transmissions with the atomically controlled standards at Boulder is always m.aintained, even through transmitter outages. Each antenna consists of four guyed masts 400 ft high , placed in a diamond arrangement 750 ft wide and 1880 ft long. An insulated network of aluminum. cables is suspended from each group of four masts . A down lead is suspended from the center of the cable network. present computed radiating efficiency is 2.2 percent at 20 kc/s and 24.6 percent at 60 kc/s. operating schedule is to be con tinuous on both frequencies except for reguhLr maintenfLllce periods. Station IVWVL is operated on an experimental program of b roadcasts to facilitate VLF propagation and timing resefLrch, K eyed canier station identification in International Morse Code is used . Time signals on vVvVVB co nsist of seconds pulses of 5 cycles of 1000 cycle, double-sideband amplitude modula tion . On the beginning of ettch minute (,he pulse will be in creased to one-quarter second and on the beginning of eiLch hoUl' the pulse will be thl'eequarters of tL second in dura tion. Modulation of 500 cis is used to identify the stiLtion in In tema tioIliLl Morse Code. Following the s tfttiOll call letters will be ft letter, either M or P (standing for minus or plus), and a Lhree digit number. This informa tion gi \'es the rela t ionship of the carrier frequency to atomic frequency. For instance M 130 m.eans that the carrier frequency is lower by 130 parts in 1010 than the United States Frequency Standard, This offset is incorporated to enable clocks run by the broadcas t frequency to keep time approximating Universal Time which is commonly used over the world. number is broadcast because this figure changes nearly every year and could change more often. It serves as a reminder to the user that the full fLccuracy of the transmissions can only be realized with proper corrections. 60 kc/s signal is provided as a continentftl service of the National Bureau of Standards. 20 kc/s signal is largely experimental. Both signals are now used to steer radio station WWV wi th negligible degradation of accuracy.