Don,
Can't argue with this. A long time ago a wise engineer said: "Never
believe the last digit displayed". He was talking about the newly
released 3 and 4 digit equipment display. Today it's almost as you say.
Believe the first two.
There are some exceptions to this rule. HP equipment (at least the
older stuff) would only digitally display the number of truly believable
significant digits. For example, their counters would not display all
available digits but just those one can real. So there are exceptions
to all rules of thumb.
One has to know their measuring gear characteristics to know what to
believe.
73 de Brian/K3KO
On 6/6/2016 0:37 AM, Don Wilhelm wrote:
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?
______________________________________________________________
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]
