I recently transplanted some guts from a radio controlled clock

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I recently transplanted some guts from a radio controlled clock and stuck it in anohter clock that's in an awkward place and often gets forgotten. The ultimate goal is to stick a solar cell in the clock and just leave it to exist. Unfortunately, the clock I transplanted the guts into is all metal, so the radio controlled parts are having troubles pulling the signal. I read about passive resonant loop antennas that you could make and just stick in your attic, and field concentrator antennas that you put behind/near the clock itself to help the signal.
The clock itself has a thin wire looped and waxed around a ferrite rod. in the back of the clock module. What can I do to try and beef up the signal? How would I go about calculating and making those antennas?