Phil, With each LED representing 100-watts on the 2KW scale, it may be of some help to go from 10% to 5% in accuracy, but in the case of the W2, the display resolution is limited to 50-watts in between mid power ranges (e.g., 250-watts) but a display of 200-watts with two LEDs showing may actually mean 151 watts or 249 watts.
50-watts is mid-way between any two LEDs at the 2KW range and I'm making an assumption that levels less than any 50-watt range (e.g., 240-watts) will result in the preceding element being lit which shows 200-watts. If it's more than the mid point (e.g., 260-watts) then the next LED should be lit. So, at the low-end of the W2's range at say the 200-watt level, the meter can at best resolve to only 50/200 = 25% and seemingly 100/200 = 50% at worst (using the 149W to 249W example). I don't want to confuse resolution with accuracy but the two parameters go hand-in-hand. That said, I see no real benefit of going from 10% to 5% in accuracy when resolution deficiencies can easily mask the error in accuracy. I may be completely wrong with the manner in which the W2 resolves, so someone set me straight if my assumptions aren't correct. You asked the question about what it takes to achieve better accuracy. You may want to read N8LP's excellent article in QEX from a few years ago, along with articles from Warren Bruene, Roy Lewallen, John Grebenkemper, and others who have published on the accuracy subject. Paul, W9AC ----- Original Message ----- From: "Phil Hystad" <[email protected]> To: "Elecraft" <[email protected]> Sent: Wednesday, December 09, 2009 7:51 PM Subject: [Elecraft] W2 Questions >A few questions about the W2 meter: > > 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. > Is this full scale accuracy and if so is half scale possibly more accurate > or is this the most accurate the meter is likely to be. I am not even > sure if it makes a difference for full scale or half scale for a digital > meter so that part of my question may be moot. > > 2. What does it take to achieve an accuracy better then 5 % (for > example), and is it possible to achieve an accuracy of 1 % or better? I > am curious as to where the money needs to be spent in achieving such > accuracy. Is it in the directional coupler? > > 3. I am thinking that the company that can build the best receiver on the > market (the K3) can also build the best meter. So, would Elecraft > principles consider a future super-accurate, best on the planet, amateur > radio RF/SWR power meter? Oh, I think a current meter would be cool too. > > And, I know that having meter accuracy is of little importance in ham > radio but there is some kind of deep seated quirk in me that wants > accuracy just for the heck of it. Certainly 5 % is achievable, right? > > 73, > phil, K7PEH > ______________________________________________________________ > 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 > ______________________________________________________________ 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
