The MFJ-916B duplexer is a series of inductance coils and capacitors that act
as a band-pass filter. Your MFJ duplexer can be used two different ways. The
duplexer combines the output of the HF/VHF transceiver and the output of the
UHF transceiver so that both transceivers can be connected to the same antenna.
The duplexer can also be used to separate HF/VHF transmissions from UHF
transmissions so that one transceiver can be connected to two antennas.
The MFJ-916B is designed for indoor use. If you use the MFJ-916B outdoors,
it should only be used for short periods of time under good weather conditions.