The Shakespeare 4357-S Diplexor
is a great device to permit
the VHF antenna
to provide service
to the VHF
receiver / transmitter and service
to the AM / FM receiver.
It is an unpowered, passive device that inserts between the VHF and the VHF antenna
that splits-out and routes the AM / FM band to the radio
white providing normal operation to the VHF radio
This diplexor was installed by the factory on my boat and has been providing terrific service and utility. I have retained usage of this diplexor, even after upgrading both my VHF and my stereo.