[Elecraft] K3 voltage reading

[Scott Ellington]

On Nov 17, 2010, at 9:26 AM, Don Wilhelm wrote:

>  The K3 display reads the voltage after 
> the protective diode,


I don't think so, but correct me if I'm wrong.  The measured voltage appears to come from 12PA through a 4:1 voltage divider, which produces V12SPA, on the KPAI03 board.  The only internal components I see between the 12 V power connector and the measurement point are the 0.005 Ohm shunt on KPAI03 (R3), and RFC6 on the RF board.  The drop across R3 would be 0.1 V at 20 A.  I don't know the resistance of RFC6, but I suppose it could account for another 0.1 V drop.

73,

Scott K9MA




Scott Ellington
Madison, Wisconsin
USA