Tnx, John! An exercise that I've yet to find the time to do is to put the balun (or external tuner) inside a well insulated enclosure and then measure the temperature rise. (Something like a tightly closed Styrofoam box.) It's possible to get a good idea of how many watts of dissipation are needed to do that, hence how much power is being lost. The power can be calculated or, for the more empirically-minded, a resistor in the enclosure can be heated with a known DC power to produce the same temperature rise curve without RF present.
Of course you can lose 1/2 to 3/4 of your RF in the balun and the other station may not notice. After all, that's only about 1/2 to 1 "S-unit" at the receiver. Just intuitively, I'd be astonished if that balun heating was caused by anywhere near 50 to 75 watts of power being dissipated! The QRP community has a saying, borrowed from Ben Franklin of kite-flying fame (among other exploits). They say "a dB saved is a dB radiated". Or, as another sage put it, "lose a dB here and a dB there often enough and pretty soon you're talking serious losses!" I certainly live by the rule that it's good sense to avoid unnecessary losses wherever it's practical to do so, and not to panic over those losses that are unavoidable. After all, to paraphrase another sage, "...a little RF goes a long way..." Ron AC7AC -----Original Message----- Just passing along some information that might be of interest. I have the K3 with the auto tuner built in. My antenna is a Cobra Ultralite fed with ladder line. I can switch between a Johnson Matchbox and a BL2 balun/KAT3 to feed the antenna. I previously had adjusted the feedline length so that the Matchbox would find a 1 to 1 match on all bands 80 through 10 including 30, 17, and 12 meters. I have received many good signal reports on all bands with either matching system. I brought home an Omega temperature monitor and put the thermocouple inside the core of my BL-2 balun (set to a 4 to 1 ratio). I just had a 30 minute QSO on 20 meters with the K3 set to 100 watts. The balun temperature started out at 74 degrees. By the time the QSO had ended, the temperature was up to 120 degrees, a 46 degree increase. The same kind of thing happened on 40 meters. I have not yet tried another band. Signal strengths on both ends were 569 to 579. I once did an A/B comparison at 10W on several bands with the KAT2/BL2 vs. the Johnson Matchbox and there was no real difference on the other end. That was very subjective, though. The balun loss may or may not be that noticable on the other end. Happy 4th of July. 73, John W2XS -- View this message in context: http://www.nabble.com/BL2-Balun-Heating-tp18285067p18285067.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 _______________________________________________ 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
