[Elecraft] KXPA ATU Operation

[maxwelltl at aol.com]

I think I am having some issues with my KXPA 100, possibly the ATU.  Could someone please verify or refute these findings? Here is what I am seeing:


1) 25W and SWR LEDs linger on for 1.5 to 2 seconds after key up. They just stay on, then fade, flicker, and finally go out.


2) The ATU seems to tune about .1 to .2 SWR units below the KX3 ATU.  It doesn't seem to be as fast either and struggles more to get a good match.


3) The AMP switches out during a tuning cycle. I am seeing about a 1.5 second delay in switching the amp back in after tuning.  If I tune and then immediately transmit, I sometimes get caught transmitting at the tuning power level with the amp switched out.  There is a distinct click when the amp switches back in.  Perhaps a relay is hanging up.


4) I am seeing instances in which the amp will tune with an SWR of 1.2 and if I operate at low powers the LEDs on the amp indicate this low SWR.  However, when I turn the power up to 30+ watts, I am getting erratic SWR indications in the 2-3 range on the amp LEDS.  The display on the KX3 still shows 1.2 but the LEDs and the KXPA100 utility show the higher SWR as the last SWR.  The power out seems to fluctuate with the higher SWR indications also.  It is like the ATU is dropping tune at higher powers.


I am wondering if maybe I have some RF getting into the control cables.


Tom/AE5QB