We've seen the same issue with the KX3 for years... B.
On Thu, Jun 11, 2026 at 12:03 PM <[email protected]> wrote: > Send Elecraft mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > http://mailman.qth.net/mailman/listinfo/elecraft > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Elecraft digest..." > > > Today's Topics: > > 1. KAP1500 High SWR wen unkeying with FT8 (Ac9c) > 2. KAP1500 High SWR wen unkeying with FT8 (Andy Durbin) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 11 Jun 2026 12:48:31 +0000 (UTC) > From: Ac9c <[email protected]> > To: "[email protected]" <[email protected]> > Subject: [Elecraft] KAP1500 High SWR wen unkeying with FT8 > Message-ID: <[email protected]> > Content-Type: text/plain; charset=UTF-8 > > Hi All - I'm new the this list after recently purchasing a used KPA1500. > The KPA1500 has been working well on 6M with my IC7300. Last night it > started indicating High SWR at the end of FT transmission when unkeying the > amp.? The SWR of the antenna is 1.3:1 and the amp is fine during from keyup > of each transmission up until the radio unkeys the amp.? I'm using the RCA > to RCA keying line from the IC7300 to the KPA1500. Any ideas? > Mike Taylor AC9C > > ------------------------------ > > Message: 2 > Date: Thu, 11 Jun 2026 15:30:20 +0000 > From: Andy Durbin <[email protected]> > To: "[email protected]" <[email protected]> > Subject: [Elecraft] KAP1500 High SWR wen unkeying with FT8 > Message-ID: > < > ph0pr10mb7062df5a5a756e133d55a9b38c...@ph0pr10mb7062.namprd10.prod.outlook.com > > > > Content-Type: text/plain; charset="iso-8859-1" > > I had a problem with high SWR when unkeying a TS-590S used with KAT500 and > KPA500. It was a challenging investigation. > > I found that, due to the failure of an electrolytic capacitor, my TS-590 > was emitting a short burst of RF on a completely spurious frequency when it > was unkeyed. The failed capacitor changed the rise time of a TX/RX > switching signal and resulted in an unintended oscillatory loop. > > The spurious frequency was way off the frequency to which my antenna was > tuned so I received a high SWR indication. > > I'd suggest you use appropriate tools to examine the frequency of the > amplifier RF drive signal for the TX/RX transition. > > 73, > Andy, k3wyc > > > > > > ------------------------------ > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > http://mailman.qth.net/mailman/listinfo/elecraft > You must be a subscriber to post. > Elecraft web page: http://www.elecraft.com > > End of Elecraft Digest, Vol 266, Issue 6 > **************************************** > ______________________________________________________________ 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 Message delivered to [email protected]
