Sri Fred. I stumble around over all the K's, A's, P's et cetera myself. It's most maddening when I do it writing a manual :-)
RISING INPUT SWR TO KPA500: The fact that the SWR into the KPA500 rises with time is puzzling. That surely suggests something is changing as it heats up. However, from my experience and the comments I have seen from others, the KPA500 does *not* provide a 1:1 match to the K3 on 10 meters. Mine is 1.7:1 on 10, 1.4:1 on 6 and 12 meters and 1.1:1 or better on all of the other bands. I've not worried about it since the K3 only provides low-level drive RF to the amp anyway. I can't say if the SWR changes through steady use. Shoot, I've not had time to get on the air in over six months, and haven't worked 10 in a much longer time. KAT500 MIS-TUNING: A single "click" suggests that the KAT500 was shifting to a memorized tuning configuration or changing antennas, either of which would show a high SWR to the amp of course. But that would happen only if you changed frequency at the K3. Is that possible? Can you repeat the event? I know that you sort of did the next day, but how about if you try it immediately after the KAT500 tunes with full power running. What is the SWR into your antenna feed line? (You can see that using the Utility program.) Any chance something in the antenna system is changing on ten meters? 73, Ron AC7AC -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Fred Jensen Sent: Sunday, December 09, 2012 1:49 PM To: Elecraft Reflector Subject: Re: [Elecraft] KPA500 - SWR into K3 On 12/8/2012 7:57 PM, Ron D'Eau Claire wrote: > Well, putting the KAT3 in operation will "correct' whatever is causing > the high VSWR in the KPA500 by providing a conjugate match, but when > the KPA500 is in Standby it passes the K3 output through to the > KAT500. Now the input to the KAT500 is no longer the same value it was > with the KAT3 bypassed so it needs to retune too. Too many K's, P's, T's and A's. :-) Let's start over. 1. Original config on *all* bands was: KAT3=BYPASS, KPA500=OPER, KAT500=tuned [all segments, all bands, all applicable antennae for each band]. 2. In original config, SWR seen by K3=1.1:1 max, often 1:1. SWR seen by KPA500=whatever the KAT500 could produce, always below 1.5:1. All this is as expected. 3. Still in original config, I started ARRL 10 CW and after awhile noticed K3 SWR=1.5:1 and wondered if something had gone south in the KPA500 input circuit. Note: KAT3 is still in bypass, SWR seen by KPA500 is still 1.1:1 where it was when I started on 10M. 4. Posted a question to the list, Gary offered: "Put KAT3 in AUTO, do ATU TUNE on the K3, put KAT3 back in BYPASS. When I did this, three things happened: a) I heard the KAT3 tune, and I heard a quick relay noise from the KAT500 [not the amp], as if it *too* was adjusting. b) The SWR seen by the K3 went to 1:1 c) The SWR seen by the KPA500 was now off scale, and it faulted. 5. I then did a TUNE cycle on the KAT500, and SWR seen by KPA500 went back to 1.1:1 where it had been. SWR seen by the K3 [i.e. looking into the KPA500] remained 1:1. <digression>When I did all of the above, I was somewhere between 28000 and 28050. It was late afternoon Sat, contest activity was waning, and I ended the day without going above 28050. This AM, there was contest activity up to about 28075 or so. The first time I tried transmitting in that segment, I had to do a TUNE cycle on the KAT500, which is even more puzzling since I had already done it in that segment and the KAT500 had memorized it.</digression> I understand your reply, that's not what puzzles me: -- With KAT3 in BYPASS, is the K3 not looking directly into the input impedance of the KPA500? SWR seen by K3 should be 1:1 [or very close]. It wasn't, that's what started this puzzle in the first place. -- Obviously, I can use the KAT3 to minimize the SWR seen by the K3 ... shouldn't have to but I can. And yes, that has side effects should I go to low power with KPA500 in STBY. Remember though, after doing the ATU TUNE on the K3, *the KAT3 went back to BYPASS*. -- If "BYPASS" on the KAT3 really means what it says, the sequence: "KAT3 AUTO, ATU TUNE [on K3], KAT3 BYPASS" should do nothing to the original issue ... 1.5:1 seen by the K3 ... but it did, just like Gary said it would. -- Regardless however, messing with the load seen by the K3 should not affect the load provided to the KPA500 by the KAT500, but it seems it did. -- Why would doing ATU TUNE [on K3 feeding the amp] cause the KAT500 to do anything? I've checked all the K's, P's, T's, and A's in the above and I'm convinced I got them all right. You have to read carefully. :-)) I haven't figured out how to repeat the issue since I don't know how to get the KAT3 back to whatever it was doing in BYPASS when this all started. 73, Fred K6DGW - Northern California Contest Club - CU in the 2013 Cal QSO Party 5-6 Oct 2013 - www.cqp.org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
