La Crosse Technology Weather Station Instruction Manual page 12

If the tower icon flashes, but does not set the time or the DCF tower does not appear at all, then please take note of
the following:
Recommended distance to any interfering sources like computer monitors or TV sets is a minimum of 1.5 - 2
meters.
Within ferro-concrete rooms (basements, superstructures), the received signal is naturally weakened. In extreme
cases, please place the unit close to a window and/ or point its front or back towards the Frankfurt transmitter.
During nighttime, the atmospheric disturbances are usually less severe and reception is possible in most cases.
A single daily reception is adequate to keep the accuracy deviation below 1 second.
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