On Tue, 17 Apr 2018 04:17:33 -0400, George Cornelius wrote:

+AD4 Also, I wrote that you might need an antenna tuner for an external
+AD4 antenna, but this just seems to clip on directly, so that's a good sign.
+AD4 Otherwise I was going to guess that the receiver had inductive antenna
+AD4 impedance compensation, varying by band, and building just a series
+AD4 capacitor substitution box that went by decade from 50pf to 50nf might
+AD4 compensate for that in order to work with an antenna of design impedance
+AD4 of, say, 50-300 ohms.

Most portables have an untuned high impedance connection to the whip
antenna. Basically just coupled to the gate of a FET.

A high input impedance input is good enough for a rod antenna. The
antenna is electrically short at SW frequencies and the +ACI-ground+ACI half of
the antenna is whatever capacitive coupling the radio can get to the rest
of the world.

An antenna tuner would be helpful because the untuned input stage is
going to overload first on the strongest signal, which is likely a local
BCB station.