last night I discovered something about atomic reception which seems to contradict a thesis I read a few times in this forum - i.e. that the radiowaves can only enter a G-Shock through the dial - according to what I observed, this cannot be true.
Here's what happened:
- 1st I need to mention that I live only ~200 km away from Mainflingen, where the german DCF77 longwave transmitter is located, so my Casios *always* sync regardless of where I put them in the house, with the one exception of very bad weather
- yesterday I attached Maratac Elite straps to my new Pro Trek PRW-2000 (see: https://forums.watchuseek.com/showthread.php?t=323254 ) - because the straps were quite stiff and uncomfortable, I decided to strap the watch around a plastic bottle with skin lotion (which is roughly wrist-shaped) for a while to pre-bend the watchband
- to my suprise the Pro Trek did not sync that night (it always synced perfectly before)
I did some testing with manually initiated timesyncing today and here's what I found out:
- both my Casios (see sig) with radio reception synced fast (2-3min) when placed in any position at the same spot where the Pro Trek strapped to the bottle would not sync
- both Casios snyced when worn on the wrist and held at the above mentioned position (signal strength level 3!)
- both Casios did not snyc when strapped to the plastic bottle and facing roughly north-east (that's where the DCF77 transmitter is)
A plastic bottle with skin lotion is radiowave-proof.
Obviously the longwave signal does not enter through the dial only but also through the back and it can be blocked.
I don't quite understand why simple skin lotion  in a plastic bottle has this effect and wearing the watch on your wrist does nothing to disrupt the reception.
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