[Elecraft] Fix for K3 frequency shift on 2 meters when using K3EXREF option with K144XV

[Wayne Burdick]

Some users of the K3EXREF (external reference lock option) have  
reported a small, periodic frequency shift on 2 meters. This occurs  
only if a K144XV module with PLL lock module is also installed, and  
the external 10-MHz reference is connected.

There's a simple fix for the frequency shift. Instructions can be  
found on our K3 mods page:

     http://www.elecraft.com/K3/k3_app_notes.htm

73,

Wayne
N6KR