Most radio-synchronized clocks these days listen to WWVB, which is a narrowband digital-mode broadcast on 60 KHz long-wave. If you can receive it reliably (and I struggle to here in Virginia), it’s much easier to decode.
WWV regular AM broadcasts are on the usual 2.5, 5, 10, 15, and 20 MHz. But we’ve been in a low part of the 11-year sunspot cycle for the past half decade, and HF propagation is limited. But only older radio-synchronized products use those broadcasts.
I have a Marathon wall clock that has never synced properly yet.
Rick “need to make an antenna for it, but a 60 KHz antenna ain’t that easy” Denney