Terry you do not mention the lenght of your inverted L. However if it is end fed then it is unlikely to be exact 50 ohm. Then the length of coax gets important because it may do an impedance transformation.
What is happening is that your tuner works in a high impedance load and that means high voltages. Nothing wrong with your rigs / ATU, just the way the antenna has been set up. You may also find that you have RFI. You can try adding or shortening the coax lenght to see if it helps. 73, Marinus, ZL2ML G4MKP wrote: > > Problem on 80m SSB. > > > > I am experiencing what I can best describe as ATU Flashover on 80m SSB. > > > > Background - I have a K3 and Challenger 3 linear amplifier. Headgear is > the > Heil Proset plus. I can tune up the rig and amp to well in excess of 500W > without any problem. CW can be operated at full power without any > problems. > However, when I modulate the radio using SSB on 80m at anything above > approx > 275W, the SWR goes from 1:1 to infinity and I can hear the ATU flashing > over. It also occurs when modulating the radio using AFSK for RTTY > operation. Opening the ATU reveals arcing between the capacitor plates. > The > problem does not occur on any other band. > > > > Grounding - all equipment is individually wired to a central rf earth > point > which is connected to a buried copper earth rod. I have a further 4 copper > rods connected to the previously mentioned rod that are spread over a few > feet. > > > > Antenna - 80m inverted L with six radials spread over about 45 degrees. > > > > I don't have another rig at present to substitute. > > > > Any idea what's going on please? > > > > Cheers, > > > > Terry > > G4MKP > > > > > > > > > _______________________________________________ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > -- View this message in context: http://n2.nabble.com/ATU-Flashover-tp1345469p1345642.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
