[Elecraft] KAT500 Performance Clarification

[Phil Hystad]

Gang, I was surprised last night when I got a descent low SWR tuning my 80-meter (ladder-line fed into 4:1 balun) dipole on 160 meters.  I have had the KAT500 for a couple of months and I never bothered trying it on 160 meters because on all previous attempts with other manual tuners I have failed to get a good match.

But, last night, just as a lark, I switched up to 160 meters and gave the KAT500 a try.  Sure enough it found a match of 1.05:1 at 1900 KHz with the Bypass VSWR reading about 17:1.  Given I have most of the transmission line in lower-loss ladder line helps with the losses to the antenna with that high bypass SWR.

This was at 100 watts out from the K3.  Now, I decided to give a try with the KPA500 in-line at about 475 watts and the best I could get is about 4:1 tuned SWR.  Now, I am not quite sure I understand the dynamics of the KAT500 with higher power.  This is what I did.  I tuned at 20 watts to the 1.05:1 SWR (bypass was ~17:1).  At 100 watts, my LP-100A was still reading about 1.1:1 SWR.  But, when I turned on the KPA500 (switched out of standby) the reading was roughly 4:1 with a fault on the KPA500.  Question, how does the higher power affect the match of the KAT500.  I understand how higher power might stress the KAT500 with maybe arcing or something but I don't understand why the match actually changed unless that higher power caused some change in the KAT500 capacitor or inductor components.


73, phil, K7PEH