Hi, Phil. Although the KAT500, like most tuners, will attempt to find a match whenever it can, it protects itself from the very high voltages and currents that can appear on internal components when the match is poor. We rate the tuner for 500 watts at 10:1 SWR. When you use an antenna that shows 17:1 SWR (the "untuned" or "bypass" VSWR), the ATU measures the forward power and computes the power it can safely handle with the high mismatch. It's less than 500 watts. You should be able to operate safely at 250 watts or so with that high a bypass VSWR. If you exceed the ATU's safety values, it should illuminate the red FAULT led, make a fault log entry, and put the ATU into BYPASS at the next opportunity. It should also interrupt the amplifier key line.
Dick, K6KR -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Phil Hystad Sent: Wednesday, January 23, 2013 8:48 AM To: [email protected] List Subject: [Elecraft] KAT500 Performance Clarification 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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
