Are you running your K3 tuner into the amp? If so, shouldn't' the amp be giving the radio a nice match to start with? Are you running a tuner after the amp as well? If you are running the K3 tuner, turn it off. Is this on the exact same frequency or are you switching between the cw and ssb portions. What freq is the antenna tuned for?
_____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of G4MKP Sent: Friday, October 17, 2008 8:47 AM To: [email protected] Subject: [Elecraft] ATU Flashover 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: [email protected] 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
