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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.

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Most large metal structures such as power lines towers are grounded, which should make them rather poor in functioning as receiving antenna. But there may be other effects that sometimes improve reception nearby such objects.

One mechanism by which large conductor can improve radio signal is the radio signal drives oscillations of electrons in the large conductor, which in some conditions can increase electric field strength at the corresponding frequencies. That's why touching a radio so often improves the sound - human body is a good big piece of conductor.

Optimal size and shape and positioning of such a body depends on the kind of radio signal one is seeking to detect. It is a broad topic of reception antennas. The simple kind of antenna is a dipole antenna - two insulated metal rods that are arranged in single line.

https://en.wikipedia.org/wiki/Dipole_antenna

Using more of these is possible to benefit from the effect you are asking about. The most encountered kind is so-called Yagi-Uda antenna, where the signal detected by dipole antenna is enhanced by other metal rods placed at special distances related to radiation wavelength, called reflectors and directors:

https://en.wikipedia.org/wiki/Yagi%E2%80%93Uda_antenna

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  • $\begingroup$ What about simple reflection enhancing the signal? Metal is a good reflector of em waves..On the veranda , I have improved the signal to my computer from the modem inside by using a large metal bowl close by. $\endgroup$
    – anna v
    Nov 21, 2020 at 5:29
  • $\begingroup$ Is the bowl oriented in such a way so that it works like a reflector dish? Or the orientation doesn't matter? $\endgroup$
    – Ján Lalinský
    Nov 21, 2020 at 12:55
  • $\begingroup$ I just had it upside down on the veranda table and moved it around to get the stronger signal,stainless steel bowl bowl lip diameter 30cm, 15cm deep. $\endgroup$
    – anna v
    Nov 21, 2020 at 14:32
  • $\begingroup$ Interesting, I wouldn't expect that to work that well. If the computer is near the bowl, the bowl can reflect some radiation towards the computer, but due to curved shape of the bowl it goes into all directions and at the position of the wifi module is weak compared to the primary wave. But I can believe it works, just no sure how. $\endgroup$
    – Ján Lalinský
    Nov 21, 2020 at 14:52

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