Re: [K2] Remote KPA100 Bias Current Adjustment

Posted by Brian - N5BCN on May 12, 2011; 3:35am
URL: http://elecraft.85.s1.nabble.com/K2-Remote-KPA100-Bias-Current-Adjustment-tp6350558p6354410.html

Hi Don,

Perhaps against my better judgement, I adjusted the bias current of the KPA100 in the KAT100-2 remoted from the K2.  Now I'm thoroughly confused! :-(

The current measurements of the KPA100 in the K2 make sense to me:
Power < 11 W, Current ~ 380 mA
Power > 11 W, Current ~ 520 mA
Power > 11 + Fan on Lo, Current ~ 565 mA
Add 400 mA for the bias current, and you get a target of ~965 mA.


The current measurements of the KPA100 in the KAT100-2 remoted from the K2:
Power < 11 W, Current ~ 88 mA
Power > 11 W, Current ~ 229 mA

This makes sense to me because the KPA100 is providing power to the KAT100-2 now, which apparently draws a lot less current than the K2 plus options.

Here's what doesn't make sense to me:
Turning on the fan now that it's in the KAT100-2 does not increase the KPA100's current draw at all, but it makes the current draw of the K2 go up!

The only connection between the K2 and the KPA100/KAT100 is the data cable connecting the RS-232 ports.  Is this data cable providing current to power the fan?!  If so, how do I factor all this into figuring out a target for the bias current adjustment?  Do I add 400 mA to the 229 mA value and be done with it?

Thanks for straightening me out!!

73

N5BCN - Brian