At high signal levels coming from the antenna, overloading can occur. A poorly dimensioned RF preamplifier can be completely overloaded or mirror frequencies occur at a distance of the double intermediate frequency, i.e. a station falsely appears a second time on the dial and can even mask a weak desired signal.
With high quality receivers, the radio frequency amplification can be reduced using the RF Gain control, but additionally an attenuator can often be activated, which attenuates the signal by 10 - 20 dB close to the antenna input.
More simple sets have a LOCAL / DX switch, often near an external antenna input; in the LOCAL position, the attenuator is effective.
In case of a questionable mirror frequency reception, the attenuator can be switched on or the LOCAL position selected, if the station then disappears, you receive a „ghost signal“.