On Feb 18, 2012, at 5:43 PM, Don Wilhelm wrote: > Rick and all, > > Look for something in the antenna system that is arcing over above the > 80 watt level (or whatever level the problem starts). Check every > junction in your antenna system. Your workaround may be OK, but the > real fix may increase your antenna efficiency.
That's where I first started. I replaced the ancient twin lead with new open wire. No change. I replaced the 4:1 balun with a new 1:1 balun. No change. I replaced the coax to the balun. No change. I inspected the center insulator, that's a block of quarter inch PVC with everything separated at least two inches. I checked the end insulators. They look fine and they are tied to Dacron line. The ONLY thing I didn't change is the antenna wire ;-) The antenna is in free space with the closest object being the antenna mast a foot away. What did stop the problem is changing rigs (to a TS-440) or changing the antenna tuner (to the Palstar). What's in common with the problem? The K3. > > The other situation that will cause "bad behavior" above a certain power > level (and on a particular band) is common mode RF coming in from the > antenna and its feedline. The SWR sensing circuits may "go crazy" in > the presence of too much RF voltage. In this case, the use of common > mode chokes at the antenna, and possibly at other points along the > feedline may be what it takes to "tame the beast". Now that sounds like a possibility. Ken WA8JXM ______________________________________________________________ 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
