Bob, The scale calibration --is-- compressed to the right of center, --not-- to the left as you state, making the left portion expanded and easier to read.
73! Ken - K0PP On Sun, Aug 23, 2015 at 2:14 PM, Bob McGraw - K4TAX <rmcg...@blomand.net> wrote: > > This seems to have things really screwed up. Yes, the Bird 43 is a 5% of > F.S. accuracy instrument. The Bird 43P is somewhat less accurate, > although 5% F S with carrier, and more like 8% F S or so in peak mode. > In measuring a 100 watt radio with a 100 watt F S slug would seem to be > most accurate. Total accuracy decreases as the indicated value > approaches the left side of the scale. Now using a 250 watt slug to > measure a 100 watt radio, the earlier states that most accuracy is to the > left of center, which by the way, is the compressed side of the scale. > This makes no sense as the scale markings are much more difficult to > approximate. In fact the most accurate area is to the right of center > toward full scale is the expanded scale which is where the highest > accuracy actually occurs. With a 100 watt radio and a 100 watt F S slug > the error is +/- 5 watts at 100 watts. Using a 250 watt element and > measuring 100 watts near center scale the error is more like +/- 12.5 watts > or 5% of the F S value. > > If one measures the same power source with identical elements and gets > different results, they should refrain from buying ham fest elements for > indeed the elements are not identical. To wit, I purchased 3 new 100 watt > elements and 3 new 2500 watt elements. They all give identical results +/- > the width of the pointer. I don't buy ham fest Bird elements as I find > they are junk and not worth the brass they contain. > > And remember, Bird 43 instruments are calibrated for only a 50 resistive > load. Any other load being used leaves one with a "best guess" situation > as to actual power. > > 73 > Bob, K4TAX > K3S s/n 10,163 > > On 8/21/2015 11:48 PM, Wes (N7WS) wrote: > So by your "logic" it would be best to measure one Watt using a 100W >> element. >> >> On 8/21/2015 8:03 PM, Ken G Kopp wrote: >> >>> Bird accuracy is specified to be +/- 5% of meter full scale ... a 100W >>> element would be a poor choice to measure a 100W output level. Take a >>> look >>> at any Bird's meter scale. It's not linear and can be read with the most >>> accuracy to the left of center scale. A 250W element is much better for >>> measuring 100W. >>> >>> Wanna chase your tail? Measure the same power source with identical Bird >>> elements...... >>> >>> Don's method is better, but all methods are obviously subject to the >>> accuracy of the final indicating instrument. >>> >>> FWIW ..... >>> >>> 73l >>> >>> >>> >> ______________________________________________________________ >> 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 >> Message delivered to rmcg...@blomand.net >> >> >> >> > > ______________________________________________________________ > 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 > Message delivered to kengk...@gmail.com > ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
