I strongly suspect you have a common mode problem. These can be very frequency dependent.
Read: http://audiosystemsgroup.com/RFI-Ham.pdf especially the section on common mode chokes. There is a cookbook near the end for band specific chokes. For more details on the math read: http://fermi.la.asu.edu/w9cf/articles/balun.pdf I'd also recommend you take out the 4:1 transformer. Good luck jim ab3cv On Tue, Jan 8, 2013 at 8:06 PM, Ron W3ZV <[email protected]> wrote: > At least I'm pretty sure its an RFI problem. I have a K3, KAT500 and the > KPA500 connected as recommended with Elecraft DB15HD cables. The antenna is > a 120ft. doublet fed with ladder line to a 4:1 balun and 10ft of coax to > the KAT500. I have a comment point ground to a ground rod six foot from the > shack. I have operated the amp at 400+ watts from 80m to 6m. The only band > that gives me a problem is 12m. When I am operating at 400 watts ssb, the > amp will fault with a high swr indication within 5 to 20 seconds. > Immediately prior to the fault the swr on the amp display was 1.2:1. > Reducing power to below 300 watts seems to avoid the problem. > > Assuming the consensus is that this is RFI, what would be the most likely > suspect? Coax cables in/out? DB15HD cable? Power cable? What's the easiest > way to diagnose and correct the problem? Thanks > > Ron W3ZV > > > > > ______________________________________________________________ > 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
