I recently acquired a National NC-125 receiver with no speaker. What is the
impedance of the matching speaker that National used to sell for it? Is
there a clear downloadable schematic available? I downloaded the operating
manual from bama, but the schematic and parts placement diagrams aren't very
clear.

73,
Bob AD3K

The NC-125 has a 3.2 ohm output - but you can use 4 ohms, 8 ohms. There is
not much difference. The audio quality of the NC-125 is "communications"
quality, so the speaker does not matter much.

Basically, any old radio speaker ought to work. I expect 95% are just the
right impedance.

Colin K7FM