Radio clocks are vulnerable to signal loss and spoofing regardless if it is GPS, cellular, or HF. If the time accuracy is critical, then the time signal should

Radio clocks are vulnerable to signal loss and spoofing regardless if it is GPS, cellular, or HF. If the time accuracy is critical, then the time signal should be delivered by wire to device, especially indoors. Wall clocks should have a manual way to set the clocks given there has never been a guarantee to receive the WWV signal. If expense is the concern along with wireless capability, then an integrated 2.4GHz SoC could be used that costs pennies; https://www.beaglesoft.com/radsynreceiver.htm https://www.beaglesoft.com/radsynreceiver.htm appears to cost hundreds.