Evert wrote: 2) Can this amplifier be tuned for 1 hour on a dummy with full output at any band without any semi-irreversible side effects?
---------------------------------- If you mean at the rated output for 100% duty cycles modes, 40 watts out, the answer is Yes. But I'd not try it at 100 watts. The 100 watt spec assumes you are running SSB or CW that has a much, much lower duty cycle, so the average power output remains 40 watts or less. Several years ago I helped test the VCO stabilization mod and needed to temperature-cycle the K2 as in normal heavy use. I did that be transmitting into a dummy load for periods of 1/2 hour to 1 hour, occasionally longer. I ran the K2 at 100 watts and keyed it in CW, using a repeating CW memory to keep it running. The internal air temperature between the KPA100 and main K2 PCB got up over 50C (120F). The KPA100 heat sink was too hot to hold my hand on it. Since the intent was to simulate very heavy use of the rig in a real situation, I did not provide any ancillary cooling. I did that dozens of times. No problems were encountered. I did not run those tests on various bands, so I can't speak to any significant temperature differences. But there are some slight differences in efficiency. Does your KPA100 make a full 100 watts output on all bands? If not, there might be a problem with your output filter on one or more bands that is reducing the efficiency more than it should. That would produce excess heat as well. If you are getting full rated output, I'd expect that any differences noted are normal. Be sure to tighten your final PA transistor mounting screws after several hours of operation as described in the manual. That ensures you maintain the intimate mechanical contact needed for efficient heat transfer. It only needs to be done once. I think my screws took about 1/2 turn after the rig was run in for several hours, then they remained "snug". As others have pointed out, there is exit cooling cleverly hidden between the fins on the KPA100 heat sink at the forward end. So if you use the heat sink to keep your coffee cup warm, don't spill any! 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
