Multiband Antennas in Receive Mode
By Muliband I mean antennas that are resonant on more than one band at the same time. This includes nearly all beams which may be the only exception because they exhibit gain and front to back ratios.
Normal wire antennas that use traps, special impedance matching devices like the Windom, or other schemes that allow multiband operation without the need for an antenna tuner, are systems that qualify as multiband antennas being considered here.
While it can be convenient to change bands without need to change antennas we need to realize that such a system allows the receiver to be bombarded by signals from multiple bands in addition to allowing the transmitter to operate without need for antenna tuning.
Is this a problem? Maybe not, but it raises questions about the efficiency of a multiband antenna system. At the very least, such an antenna is far more susceptible to picking up unwanted signals and other noise when compared to a system using an antenna tuner.