I have had similar problems with swr trips on my KPA500, only after several transmissions on some bands. By a process of elimination it was traced to a toroidal voltage heating up in an external coupler. It came on suddenly after about 5 minutes of transmissions, and came good after a few minutes to cool. Replacing the toroid with a larger one cured the problem.
"Ron D'Eau Claire" <r...@cobi.biz> wrote: > Hi Dave: I thought you said it happened after you sent CQ+Call a few > times. When a core heats to its Curie temp, the inductance change happens > "instantly". You are right - if it happens instantly when you hit the key > it is not heating. Something is breaking down. > > 73, Ron AC7AC > > -----Original Message----- From: Elecraft > [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Dave Cole Sent: > Saturday, May 13, 2017 10:39 AM To: elecraft@mailman.qth.net Subject: Re: > [Elecraft] Strange SWR change on 20 at > > I added the SWR meter... My actual SWR jumps instantly up about1 SWR > unit... I believe it is a bad connection on the Challenger where the main > antenna connects to the 20 meter tuning stub... > > Just sort of surprised me to see a second person with the exact same issue > is all... SWR change is instant, so it is not heating... Happens at 30 > watts, or 1 KW... Time for a rebuild. > > 73s and thanks, Dave NK7Z http://www.nk7z.net > > On 05/13/2017 10:07 AM, Dave Cole wrote: > > Hmmm... I am having the exact same issue... My SWR changes after a few > > transmissions, then returns... Up until now, I have been suspecting my > > antenna... Time to add an external SWR bridge between the tuner and > > antenna as a permanent thing... > > > > 73s and thanks, Dave NK7Z http://www.nk7z.net > > > > On 05/13/2017 09:07 AM, Terry Brown wrote: > > > I recently started using my horizontal loop that is about a full > > > wavelength on 80, for 20 meters. I took down my yagi as we are > > > moving; drat! My Horizontal Loop is at 40 ft. height and fed with > > > 450 window line into a 4:1 voltage balun with about 15 ft. of coax to > > > rig. > >> > >> > >> > > > I am running 100 watts through my KXPA100. I tune a frequency in the > > > CW portion of 20 to about 1.2 :1 and start sending CQ. After about 3 > > > to 4 3x3 CQ's,, the SWR goes off the charts and power drops to zero. > > > I can retune the antenna and the process repeats itself. 20 meters > > > is the only band affected. > >> > >> > >> > > > I am wondering if I am having RF problems in that part of the 20 meter > > > bands This only occurs on 20 meters. The Amp is grounded, but the KX3 > > > is not bonded to the Amp. > >> > >> > >> > > > I would appreciate any advice. > >> > >> > >> > > > Thanks and 73's, > >> > >> > >> > > > Terry de N7TB > >> > > > ______________________________________________________________ > > > 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 Message delivered to > > > d...@nk7z.net > >> > > ______________________________________________________________ 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 Message delivered to d...@nk7z.net > ______________________________________________________________ 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 Message delivered to r...@cobi.biz > > ______________________________________________________________ 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 Message delivered to > gro...@planet3.freeuk.co.uk > > -- Brian Duffell Yarm England ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
