Chuck,
That is 5% of full scale with a recently calibrated slug.
Another way to look at that percentage of full scale is to consider a
200 watt slug. The error can be as large as 10 watts *anywhere* on the
scale. That is why I don't buy Bird wattmeters at hamfests unless it is
cheap enough to send to a calibration lab.
At least a digital wattmeter retains its accuracy as a percentage of the
reading - a very different specification. Yes, +/- 20% is up to 40
watts error at 200 watts, at 10 watts, the error is only 2 watts.
Many of the digital wattmeters like the Telepost LP100 can boast of 5%
accuracy because they are calibrated with NIST tracable instruments.
Elecraft does use the LP100 at many of the technician workbenches.
73,
Don W3FPR
On 3/19/2018 3:39 PM, hawley, charles j jr wrote:
Bird advertised and prints in the manual +/- 5% of full scale power. I remember
some digital meters ARRL tested a few years back that did not do that well. Are
your numbers something you experienced?
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