I have a watch (Casio G-Shock GW-M5610 ) which can synchronize itself to radio time signals. In my area it uses DCF77 tower, which transmits 77.5 kHz (approximately 3868.3 m wavelength) signal:
The DCF77 station signal carries an amplitude-modulated, pulse-width coded 1 bit/s data signal. The same data signal is also phase modulated onto the carrier using a 512 bit long pseudorandom sequence (direct-sequence spread spectrum modulation).
The quality of reception in my area is moderately bad so I routinely synchronize my watch when I go outside. I have noticed that the best reception and fastest synchronization is achieved by standing in a somewhat open place near (at a distance of a few meters) large metal installations like street light pole or a particular high steel frame tower which hosts local store electrically-illuminated sign. However, I was unable to conclusively separate effects from standing in an open place and standing near large metal objects.
I'm interested if large metal objects improve radio reception near them, what's the mechanism and what are the optimal dimensions and shape of a metal object to improve radio reception of a particular wavelength when standing nearby.