On Jul 17, 2006, at 3:00 AM, Tom W8JI wrote:
>
>> Well, I stated what I have used for measurement, and I
>> realize that the Bird
>> and Nye Viking are not a Hewlett Packard. I can accept
>> that both meters may
>> be off by 10%, even though their accuracy is supposed to
>> be about half of
>> that.
>
> One thing I have learned doing RF measurements almost every
> day for 30 years or more is RF measurements are tougher to
> do than most imagine.
>
> The accuracy of a Bird 43 meter, when properly calibrated
> and used, is + or - 5% of full scale anywhere on the scale.
> Since they do not manufacture a 1500 watt slug, the best we
> can rely on is + or - 125 watts at any power level with a
> properly calibrated 2500 watt slug. Many people would be
> surprised at how far off a new Bird 43 and slug combo can
> be.
Good points, Tom. However, as I recall, the spec is 5% of F.S. plus
5% of reading, so the accuracy would be +/- 125w plus +/- 75w = +/-
200w for a 1500w measurement.
>
> I know of several manufacturers that had great difficulty
> making 1500 watts (measured by accurate means) with pairs of
> 3-500Z's when only 100 watts of exciter power was available.
> HV had to be over 3500 volts.
IME, in linear operation, with 3000vdc it takes c. 140w to drive a
pair of 3-500Zs to full throttle.
>
> 73, Tom
>
>
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R L MEASURES, AG6K. 805-386-3734
r@somis.org
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