I wrote an article for NCJ on just such a project. Mine was a 6x2 with lockout
logic to prevent connecting both radios to the same antenna, and it also has an
LED display that indicates antennas in use/available. You can certainly adapt
it to a 4x2... email me off list for questions. Incidentally, this system is
still in use in my shack!
An Antenna-Switching System for Multi-Two and Single-Multi
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