On Sat, 7 Feb 2009 02:38:36 -0800 (PST) AD6XY <m.j.wil...@rl.ac.uk> wrote: > > It is a common misconception that Bird Thrulines are a always accurate. > > They are good when operated into a matched load and when the signal does not > have a high harmonic content. If there is reflected power you need to make a > correction. If there are harmonics, even if at a low level, the sensor can > read much higher power than is actually present, even into a well matched > load. Bird Slugs can become damaged, mechanically or electrically and I have > even come across ones with the wrong label. > > So, I dispute any claim of accuracy of a power meter just because it is a > good make. All power meters can on occasion give incorrect readings. > > The Bird 43 claims 5% of FSD accuracy. On a 250W slug an error of 12W. 180W > could, within the meter specification be 170W. Then the 250H slug also has a > frequency response. > > To the problem in hand: > > The low pass filtering in the K3 should prevent any over-reading being the > harmonics, unless there is a problem in the filters and assuming there is > not a mis-match, we have to assume this power is real. > > Specs indicate approx 18A at 13.8V, which is 250W input for 100W output. To > get 170W or even 180W output is possible, but I think the PA is unlikely to > be linear or long lived if used in this state. If the K3ALC is not working > the PA may well develop this much power. I would re-visit the power > calibration using the K3 utility. If that fails there is probably a fault. > > A linear amplifier designed for SSB will normally be capable of much more > power than it's linear specification. Quite possibly double on the lower > bands where the efficiency may be higher. While the amplifier can produce > that power, the device may not survive the extra thermal stress. > > Mike ******************************************************************************
Mike OC, Many, many thanks for a logical/definitive explanation!!! Appreciated it greatly! Jim/ee S/N 2406 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
