Radio WC6W wrote:
> Does anyone on the group happen to know of an algorithm that would
>generate the angular spacing of the Bird wattmeter scale markings?
>
> The square root of the value is close... but, not exactly correct.
Paste this function into Excel:
I = 30 * (-7.378E-12W^6 + 2.547E-09W^5 - 3.407E-07W^4 + 2.248E-05W^3
- 8.188E-04W^2 + 2.692E-02W - 2.749E-05)
where I = meter current (uA)
W = power (on a 0-100W scale)
That polynomial is Excel's best fit to a table of measured meter
readings (W) versus DC current (uA). (Some terms are probably
negligible, but Excel doesn't care and we don't need to either.)
I used that function in Excel to generate a set of angles for the major
scale points, which were then fed into AutoSketch... manually, slowly
and painfully... to draw a scale for a completely different meter.
Come to think, why don't I e-mail that function to WB6BLD and ask him to
incorporate it into his meter-scale drawing program?
http://mywebpages.comcast.net/tonne/
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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