Hi, Don. I suspected as much. Precision (number of digits) and accuracy (compared to a known standard) are very different. I guess it doesn't matter what the power level is except when running QRP where one must be below 5w. That's why I always adjust my power output to be 4.5 w just to be sure.
I'm sure you remember slide rules used in engineering schools before the pocket calculators came along in the 60's. I still have mine and when I look at remember some of my colleagues that would read to 5 digits from their "slip-stick". BTW: it was amazing to watch the K3 run through it's TX Calibration. After having the K3 for a few years, I'm still learning. What an amazing feat of engineering. Clark WU4B On Sun, Jun 5, 2016 at 8:37 PM, Don Wilhelm <[email protected]> wrote: > Clark, > > The detection diodes in the K3 (and the LP100A wattmeter as well), do not > have a perfectly linear relationship vs. frequency response. > The LP-100A is quite good, but can be in error by as much as 5% (Larry > will not guarantee it closer, I have asked). > The K3 wattmeter can also have up to a 10% error in its readings (may vary > with frequency). > > So the net of what I am trying to say is that at the 100 watt level, a > wattmeter reading between 90 and 110 watts is within the range of normal > expectations. > > We have come to be "accuracy obsessed" since the advent of digital > displays. In the days of analog meters, there was always a region of > uncertainty due to the inability to read the needle on the meter to a high > degree of accuracy - parallax effects, the width of the needle, as well as > the inherent accuracy of the circuits the meter was indicating. In todays > world of digital displays, we assume that all displayed digits are true and > accurate, when in truth, only the first two digits of the display are valid > in an instrument that measures to a 10% accuracy. > > 73, > Don W3FPR > > On 6/5/2016 6:49 PM, engineercm wrote: > >> Noticed today 20m output measured by LP100A was 90w when K3 wattmeter set >> to >> 100w. Same with 10m; other bands measured close enough. Updated firmware >> to >> latest and performed Transmit Calibration. Calib:WM HP at 50w set to >> agree >> with LP100A. In order to get 100w on LP100A, I have to crank the K3 >> output >> so that it reads 110 on the internal wattmeter. Why? Slope effect of >> internal WM? >> >> >> > -- 72, Clark WU4B QRPARCI #10815 SKCC #3892 Southeastern DX Club <http://www.sedxc.org> North Georgia QRP Club <http://www.nogaqrp.org> Kennehoochee Amateur Radio Club <http://www.w4bti.org> *"It is vain to do with more what can be done with less."* *Attributed to *William of Occam (1288 AD - 1348 AD) ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
