Increasing the Modulation Depth of the WWVb Time Code to Improve the Performance of Radio Controlled Clocks
John P. Lowe, Ken C. Allen
The National Institute of Standards and Technology radion station WWVB has officially changed its broadcast format. As of January 1, 2006 the WWVB braodcast signal has increased the depth of the time code modulation to improve the performance of commercial radio controlled clocks in low signal strength areas. The increase in modulation depth effectively appears to a matched-filter receiver as if the transmitted power has increased by 2.0 dB, thus extending the coverage area where WWVB controlled clocks will work properly. This is demonstrated by an amplitude shift keyed (ASK) analysis. The results given by this analysis do not depend on the noise level or the bit error rate (BER).
and Allen, K.
Increasing the Modulation Depth of the WWVb Time Code to Improve the Performance of Radio Controlled Clocks, Proc. 2006 Freq. Cont. Symp, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50349
(Accessed December 9, 2023)