Old Tom wrote: For this to work well I would expect the wave receiver to have to be well clear of anything that could detune it (metal!) or shield it (walls, floors etc).
It is surprisingly rugged, flexible, resilliant and also picks up 60 kHz like a dream.
Ok, best not under a power line, - next to a micro wave switched on, but even inside a sturdy building with a window behind bars on the south it still syncs in the mountains just above Málaga to both Mainflingen and Anthorn.
The only thing one needs to respect is put the two antennae; the wave receiver and that in the watch, in parallel. Forget all the rest.
There is a limit to the range though. In Europe it is the Canary isles; that is about the limit with the Citizen gadget, but that is hardly reason for complaint