[Elecraft] KX1 Voltage

[mvamis at wavecable.com]

On page 62 of the manual, right side top, it states:

"You can connect any 7-14 V DC power supply or battery to 
J1, although you should use the minimum recommended 
voltage (8 V) when possible..."

Why does Elecraft recommend that the KX1 only be run with 
8 volts? That's even less that a new set of Lithium 
batteries would produce.  Any comments?

Matt - K7OE