Thanks, everyone for the helpful hints. Some additional information: This installation is brand new. The antenna has been up only a month or so. Tuner and Balun even less. Coax is newly run, and I've deliberately avoided sharp bends. I purchased the KPA500 in December, so all of this QRO is new for me (in this century at least!) I am running through a surge protectors from Alpha Delta. I will double check is is not the 200W versions! Hmmm, now that I think of it, maybe that's it??? Will check after coffee!
Any tips on how I would detect/locate any potential arcing? I do understand the nature of the antenna and the potential wide range of impedances possible with this multi-band setup. - I'm going to scan it at the balun this morning with my AIM 4300 for starters. Oh, and check/bypass the surge protector too! Thanks again, 73 de K1AY Chris On Sat, Feb 24, 2018 at 7:44 AM, Victor Rosenthal 4X6GP <[email protected] > wrote: > Just to add to all the possibilities, there could be an arc at the balun. > Most authorities suggest a 1:1 balun with a setup like this. As you know, > the impedance seen at the balun will vary all over the map, depending on > the band and the length of the 600-ohm line. > > I've calculated that the voltage that appears at that point in my somewhat > similar setup is as high as 7 kV when I'm running 1200 watts on one > particular band. A 1:1 balun designed for tuner use (e.g., one like this: > <https://www.dxengineering.com/parts/dxe-bal050h10at> or this: > <https://www.dxengineering.com/parts/dxe-bal050h11ct> > would be suitable. > > 73, > Victor, 4X6GP > Rehovot, Israel > Formerly K2VCO > http://www.qsl.net/k2vco/ > > On 24 Feb 2018 07:42, Chris Hallinan wrote: > >> Greetings from southwest Florida. >> >> My KPA500 is kicking out with REFL HI warning (high SWR). But here is the >> strangeness. My setup is K3->KPA500->40' coax->MFJ 600W remote tuner -> >> 4:1 >> balun -> open wire feedline to 80-meter doublet. In words, I have a >> remote >> autotuner feeding an 80-meter doublet fed with 600-ohm open wire line. A >> Balun Designs 4:1 balun provides the interface from the open wire line to >> the tuner. >> >> With the autotuner tuned at low power, the SWR shows 1.5:1 on my KPA500 >> and >> external SWR meter. As I run the power up to 300, 400, 500 watts, >> somewhere in there all of a sudden the SWR instantly jumps off the scale, >> into the red LEDs on KPA500, and it faults. It's as if the SWR were >> dependent on power. >> >> Even stranger, when I back the power off to say 250 Watts, holding key >> down >> the SWR is stable in the green (<1.5:1), but when I key it at CW rates, >> the >> SWR bounces into the red on every dit and eventually faults, when at >> steady >> state key down it never leaves the green zone! >> >> I fear it is the tuner falling over, but it should be able to handle the >> power. I see this on all bands from 80-20. >> >> Operating into my 20-meter resonant vertical, with no tuner, everything >> works fine. >> >> Any ideas or hints on how to correct this? >> >> Thanks, >> >> Chris >> 73 de K1AY >> >> >> -- Life is like Linux - it never stands still. ______________________________________________________________ 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]
