Keith asked: My K2 will not give more than a few watts out on 40 meters when driving my antenna. Into a dummy load it gives full power. On 30 meters with a different antenna the rig is fine. I wondered if it was a problem with the rig but I saw some other things that make me think it's an antenna problem. The antenna is a ground mounted vertical fed with 30 feet of RG-213 to a Heath manual tuner in the garage. From there, RG -8x takes the signal all the way to the shack. I go to the garage with my MFJ analyzer and adjust the tuner for a match on my operating freq. I did this and got a 1:1 match at 7040. I then went to the shack and confirmed the same SWR at the rig. Hook up the rig, key it and the SWR meter shows very high SWR. Rig is generating hardly any power out. Recheck with the analyzer and SWR is fine. Hmm. I'm thinking the issue is power related. Could it be that my antenna system has a problem that only shows up when you hit the system with a few watts and doesn't show when the analyzer hits it with milliwatts? Last night I tried it again and noticed the resonant frequency had shifted from 7.040 to 9 MHz. I think it is time for an antenna / tuner / coax review.
------------------------------------------ By getting consistently good output into a dummy load, it looks like you've eliminated the K2 as the likely source of the problem. I'd suggest you check the connector at the rig end. Problems like this tend to be associated with whatever it is you are changing to make it appear and disappear, and that seems to be associated with moving that cable at the rig end between the analyzer and the K2. The same is true for when you saw that resonant frequency jump. That much of a shift would account for the jump in SWR. Look for exactly what you touched to make that change happen. Perhaps a bad connection in one of the coax connectors? For example, one time I suddenly saw a "problem" with my K2/100 going from normal operation to "high current" and shut-off when the resettable fuse opened! I was about to tear into it when my own advice popped into my head and it gave some thought to what I had been doing. I had made some cabling changes between the rig and my external ATU. Sure enough, the PL-259 to the ATU was very loose. It worked some of the time but then the heating by the RF current or a tiny movement caused by something would make the connection open and the K2 was looking into a very high SWR and would shut down. Tightening the connector fixed the problem <G>. It is possible for a problem like yours to be power related. The RF current flowing through a bad connection can cause heating and resistance changes that don't show up at low powers or a partial short at a high voltage point in either the tuner or antenna can cause that to happen. It can be band-specific too, since RF current and voltage levels at various parts of the antenna and tuner circuit change with the band. The only thing to do there is to start working toward the antenna. Try connecting your rig directly to the tuner in the garage with a different piece of cable and see if the problem appears there. Ron AC7AC _______________________________________________ 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
