I bought a radio adapter fitting that allows you to put your backup handheld VHF (Icom, SH or Uniden, plus others?) on your boats 8' 6db aerial in the event of an electrical or main radio failure. Probably should more than double the handhelds effective range in an emergency situation (though I don’t know how to personally test this).
The fitting is SMA (male) to PL259 (F)
[not all that easy to find but I've seen them all as one]
Alternative is to buy 2 adapters [readily avail] and put them together
BNC (F) to SMA (M) and BNC (M) to PL259 (F)
Parts are often avail on ebay and well under $20,
Keep the fitting taped near the end of your aerial wire and hope it never needs to be used.
Chris