(2 Availble) The MFJ-916B duplexer is a series of inductance coils and capacitors that acts 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. $20.00 shipped. Pay Pal Preferred.