Sorry I hit Send too soon --,the 5% error with a 250 watt slug is 12.5 watts - if the wattmeter has been recently calibrtrated. So a reading of 25 watts can have an actual; power between 12.5 and 37.5 watts! This is with one of the most highly respected wattmeters -- when the power is lower than 50 watts, you can do better with simple measurement tools. 0 I prefer using the RF voltage developed across a 1% 50 ohm dummy load to give me a more accurate power reading than any analog power meter I have found.
Please take my comments in context - they are limited to a 50 ohm environment and are quite dependent on the precision of the dummy load. If I want an approximation, I will use the words provided by my word processor, but if I want to be exact, I will use the dictionary 73, Don W3FPR On 12/9/2011 8:15 PM, Don Wilhelm wrote: > Mike. but 5% of full scale for a 100 watt slug is 5 watts. That is > exactly the point being made. The error is a percentage of the Full > scale reading, and not a percentage of the actual reading. > > A 250 watt slug can have an error of 37.5 watts - whether the power > reading is at 10 watts or 50 watts > al that can be concluded it that there is some power output - the > number displayed by the meter cannot be relied on if the power is > significantly lower than the power ratting of the slug . > > 73, > Don W3FPR > > On 12/9/2011 7:11 PM, Mike wrote: >> 5% of 50 watts is not 5 watts. >> >> 73, Mike >> >> On 12/9/2011 10:32 AM, Eugene Balinski wrote: >>>> From what I understand, the meter is rated at 5% of the >>> **full scale** rating according to Bird. Full scale >>> rating, is the rating on the slug. >>> >>> That would mean that for a meter with a 100W slug, your >>> accuracy is +/- 5W (5%). So, if your wattmeter is reading >>> 50W, the actual RF power could actually be 45 or 55 W.... >>> >>> 73 >>> K1NR >>> >>> >>> On Fri, 09 Dec 2011 09:08:55 -0500 >>> Mike<[email protected]> wrote: >>>> Wait. >>>> >>>> Using a 100W slug, if you get a reading of 100 watts, the >>>> real power would be between >>>> 95 and 105 watts, right? >>>> If you get a reading of 50 watts the real power would >>>> fall in a range of less than 45 >>>> to 55 watts? >>>> >>>> Not if the 5% at full scale is the best accuracy. Or did >>>> I misunderstand what you said? >>>> >>>> 73, Mike NF4L >>>> >>>> >>>> On 12/8/2011 11:59 PM, Eugene Balinski wrote: >>>>> The accuracy of Bird elements is typically +/- 5% of >>>> the >>>>> full scale value. For a 100 W Slug, that is +/- 5 >>>> Watts. >>>>> So theoretically speaking, with 5W in, and 0 >>>> registered >>>>> on the meter, the meter is still within its rated >>>> accuracy. >>>>> Additionally on the model 43 meter, there is meter >>>> scale >>>>> end compression. To get the most accurate reading, one >>>>> would want to have the 5W reading at the middle of the >>>>> meter range, which means that one would want a 10W >>>> slug. >>>>> Unfortunately I do not believe that Bird makes a 10W >>>> HF >>>>> slug any more. Perhaps they need an Elecraft W2 ?? >>>>> >>>>> 73 >>>>> K1NR >>>>> >>>>> >>>>> On Thu, 8 Dec 2011 16:47:27 -0600 >>>>> Nate Bargmann<[email protected]> wrote: >>>>>>> From my experience, trying to measure 5W with a 100W >>>>>> element leads to >>>>>> very inaccurate readings. The Bird is most accurate >>>> when >>>>>> the reading is >>>>>> as near to full scale as possible. That means a 5W HF >>>>>> element (is that >>>>>> even available?) would be ideal provided no more than >>>> 5W >>>>>> is put through >>>>>> the meter. A 10W element would be less accurate but >>>>>> provide a safety >>>>>> margin for the meter. Even better would be to have >>>> both >>>>>> elements and >>>>>> use the 10W one to get in the ballpark and the 5W one >>>> for >>>>>> a final check. >>>>>> >>>>>> 73, de Nate N0NB>> >>>>>> >>>>>> -- >>>>>> >>>>>> "The optimist proclaims that we live in the best of >>>> all >>>>>> possible worlds. The pessimist fears this is true." >>>>>> >>>>>> Ham radio, Linux, bikes, and more: http://www.n0nb.us >>>>>> >>> ______________________________________________________________ >>>> 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 >>> --------------------------------------------------------------------- >>> Web mail provided by NuNet, Inc. The Premier National provider. >>> http://www.nni.com/ >>> >> ______________________________________________________________ >> 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 > ______________________________________________________________ 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
