Dick, Thanks, this is exactly the kind of clarification I was looking for. Now, if you or someone says this was described in the manual I will be ashamed and embarrassed. I already knew about the higher power at lower bypass SWR. But, I did not realize the lower power at higher bypass SWR.
phil PEH's iPad On Jan 23, 2013, at 9:58 AM, Dick Dievendorff <[email protected]> wrote: > 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
