Some 60 years ago I was a young engineer and ham. Semiconductors were in
a very basic form, diodes and NPN and PNP transistors. Our solutions
back then tended to be very simple.

This afternoon I gave some thought to to the problem of voltage drop due
to an inline diode. Why can't we get a small SPST relay and put a diode
in series with the coil. Then wire the +12 volts through the SPST
contacts. If the polarity of the input was correct the relay would pick
and the full 12 volts would be applied to the radio. What am I missing?

73,

Jim Campbell
W4BQP since 1953