I think you have a bad connector somewhere - I will guess there is a pl259 going into that choke balun - you may have a poorly made connection to the coax which shorts out at high power. I don't think Arcing to the tree would happen especially that abruptly.
Sent from my iPad On Nov 28, 2012, at 0:49, Ashton Lee <[email protected]> wrote: > So I am trying to get set up better on 160 meters. I now have two antennas up > (pretty well separated). One is an Alpha Delta DX A sloper hung in a tree > with a grounding wire led to a ground rod and small radial field. The other > is an inverted L on a good radial system of about 2000 feet in various > lengths of about 50 feet each as fit the yard. Both are resonant at about > 1.830 . > > The sloper loads fine all the way up to 1500 watts. The inverted L loads just > fine to about 700 watts and then causes the Alpha amp to fault out. I think I > am getting a sudden change in antenna impedance. The antenna is fed through a > 5 KW rated choke balun. The feed line exits the base between radials. I've > tried various feed line lengths, I've replaced every component in the system > except for the antenna wire. The antenna does climb along the branches of a > tall pine before L-ing outward at about 55 feet. I think the problem is worse > at night time when things are cold (and perhaps more humid). > > What I see on the amp is output power suddenly seem to surge to 2500 watts, > and reflected power jump from a few watts to over what the amp can read… then > in a flash the amp faults out. This all happens with only about 20 watts of > drive, so the amp can't actually be putting out 2500 watts unless something > very strange has happened. As I noted, using the other antenna all is good. > > I need to get the inverted L working since it seems to have substantial > receive gain vs the sloper, so I assume it will be equally better on transmit. > > All advice is welcome. Am I likely to be "arc-ing" to the tree branches? > Could the wire be the problem? Do inverted L's have trouble with full power? > The same wire worked fine for the last few years, but fed against a much > lesser radial field and run through a less dense, lower tree. > > I'll be trying everything I can think of tomorrow afternoon, starting by > trying to minimize contact with the tree branches. All suggestions welcome. > > 73 > KQ0C > Ash > _______________________________________________ > Topband reflector - [email protected] _______________________________________________ Topband reflector - [email protected]
