Looking at the specifications for the KX3 on page 51 of the manual, it says
that "Sensitivity decreases gradually below 1.5MHz due to protective
high-pass filtering", and in the installation manual for the KXAT3 it says
that "The KXAT3 also includes an automatically tuned filter for the AM
broadcast band that tracks the VFO, improving image rejection for signals in
the 0.3-1.0 MHz range."
So, it would seem to me that it's a good idea to leave the KXAT3 inline, but
that the receiver is going to be less sensitive the lower in frequency that
you go and that in some cases it may be better to switch out the KXAT3 to
avoid any additional losses through the filter, as long as large local (or
maybe not so local...)signals are not going to cause you a problem.
----- Original Message -----
From: "Jim - W6VAR"
Sent: Thursday, October 24, 2013 11:41 PM
Subject: [Elecraft] KX3 General Coverage
>I noticed when listening to AM broadcast stations that receive sensitivity
> drops, but when I go to the ATU and set it for Not-Installed, the signal
> strength gets much stronger.
> Should I "uninstall" the ATU whenever I'm listening to general coverage or
> is there a way to disengage the circuitry that seems to attenuate these
> signals when we are in the general coverage area?