ghosting is a common problem in tv reception caused by interference of a reflected signal.
aerials and amplifiers must be impedance matched to the coaxial cable, typically 75 ohms.
whenever a mismatch occurs in the interconnection between coaxial cable and some other element, part of the signal is reflected back.
next is a possible situation where whenever the distance between the antenna and the amplifier is rather big, the use of a good coaxial cable and perfect connections are needed to guarantee an acceptable picture free of ghosting.
apart of this feature, there is the option of the mrd (margin raising device) that performs as a built-in preamplifier into the junction box thus ensuring the best matching between antenna and amplification.
this option can be used since the first time the antenna is installed because it only works when it is powered, being null its influence without powering.
in other words, the mrd has no effect on the received signal when it is off but it works as the best preamplifier when it is on: