In message , Roy Lewallen
writes
N connectors don't have any dielectric in the mating region, so the pin
diameter would have to be made smaller for a 75 ohm impedance. Maybe N
connector incompatibility issues have morphed into misconceptions about
BNCs. I don't think I have any 75 ohm N connectors (assuming such
things exist) to look at.

That certainly explains why the diameter of the 75 ohm N pin is much,
much less than the 50 ohm. The two are certainly not mateable.

I must admit that, in the back of my mind, I'd occasionally wondered why
- and now, after over 46 years of successfully not getting them mixed up
too often (at work, it was a hanging offence to put a 50 ohm male in a
75 ohm female), all is clear! I don't know why it never dawned on me.
I'm fully familiar with the difference between the BNCs.
--
Ian