k7fm wrote:
>The Bird should be appreciated for what it is - a very handy piece of
>portable test equipment.
>
Agreed.
>What is good about it is that it is repeatable.
>
Do you have any evidence to back that up?
I don't have any to say whether you are right or wrong, but just
wondering how you conclude that.
>With repeatability, you can calibrate each particular unit and particular
>slug to much greater accuracy.
>
Any idea how accurate?
>It is important to remember that the Bird is a package of compromises.
>
Yes, and a pretty good set of compromises.
>Home calibration is not that difficult. For example, we can use our
>calibrated signal generator
>
What part is calibrated - frequency, or power level? The former is
possible to do very accurately quite easily at home, but the latter is not.
>to provide a reference point, then use precision
>dividers (compensated for frequency of course) to measure the voltage. A
>calibrated signal generator and a scope can also be used for reasonably
>precise calibration - then make up a calibration chart for each Bird element
>on any desired frequency.
>
I'm not sure I follow your suggested technique, but scopes are not
normally much better than a few percent on the Y-axis, which since the
errors are squared for power, I can't see that being particularly good.
And what's is 'precision divider compensated for frequency'?
Sorry, I still think Calorimetric methods are the only ones that
amateurs can use, without access to expensive and calibrated test kit.
--
Dr. David Kirkby,
G8WRB
Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/
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