[Amps] Bird Element Calibration?

[David Kirkby]

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/