[Elecraft] How to get K3 SUB frequency readout on main

[Guy Olinger, K2AV]

How do I get the K3 to put the SUB RX S-meter *and* frequency readout on the 
main RX. It's as if I hit BSET and then something else.

I know this can be done because I just stumbled into it and can't figure how 
to get it back.  This is really what I want when listening on sub RX and AUX 
RF input to lower BC bands.  It allows me to see the frequency readout down 
to Hz. This is useful for listening to AM using wide LSB or SSB to keep out 
splatter from channel up or down.

I had it but can't reproduce it....

73, Guy.