Clark,
The detection diodes in the K3 (and the LP100A wattmeter as well), do
not have a perfectly linear relationship vs. frequency response.
The LP-100A is quite good, but can be in error by as much as 5% (Larry
will not guarantee it closer, I have asked).
The K3 wattmeter can also have up to a 10% error in its readings (may
vary with frequency).
So the net of what I am trying to say is that at the 100 watt level, a
wattmeter reading between 90 and 110 watts is within the range of normal
expectations.
We have come to be "accuracy obsessed" since the advent of digital
displays. In the days of analog meters, there was always a region of
uncertainty due to the inability to read the needle on the meter to a
high degree of accuracy - parallax effects, the width of the needle, as
well as the inherent accuracy of the circuits the meter was indicating.
In todays world of digital displays, we assume that all displayed digits
are true and accurate, when in truth, only the first two digits of the
display are valid in an instrument that measures to a 10% accuracy.
73,
Don W3FPR
On 6/5/2016 6:49 PM, engineercm wrote:
Noticed today 20m output measured by LP100A was 90w when K3 wattmeter set to
100w. Same with 10m; other bands measured close enough. Updated firmware to
latest and performed Transmit Calibration. Calib:WM HP at 50w set to agree
with LP100A. In order to get 100w on LP100A, I have to crank the K3 output
so that it reads 110 on the internal wattmeter. Why? Slope effect of
internal WM?
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