On Sun, Aug 23, 2015 at 4:36 PM, Ken G Kopp <[email protected]> wrote:
> 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 > Easier to read, perhaps, but less accurate. To read 100 W with the highest accuracy, you have to use a 100W slug. (period). 73, geo - n4ua > > On Sun, Aug 23, 2015 at 2:14 PM, Bob McGraw - K4TAX <[email protected]> > 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:[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] > >> > >> > >> > >> > > > > ______________________________________________________________ > > 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] > > > ______________________________________________________________ > 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] > ______________________________________________________________ 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]
