Newer clocks use the phase modulated signal: https://www.nist.gov/system/files/documents/2017/05/09/NIST-Enhanced-WWVB-Broadcast-Format-1_01-2013-11-06.pdf http

Newer clocks use the phase modulated signal: https://www.nist.gov/system/files/documents/2017/05/09/NIST-Enhanced-WWVB-Broadcast-Format-1_01-2013-11-06.pdf https://www.nist.gov/system/files/documents/2017/05/09/NIST-... If you have AM-based clocks, you might find that these work better. However, nobody advertises which module they're using, so it's kind of a crapshoot. I specifically bought a phase modulation WWVB receiver and it reliably receives the signal every night. I also have a random $7 clock from Amazon that pretty much synchronizes every night. Living in NYC, this is truly amazing to me; I never ever got the AM signal here.