On Sun, 3 Jul 2005 11:20:01 +0000 (UTC), "Reg Edwards"
wrote:

Roy said -
I think your analysis isn't valid for two reasons. The first is that
you're relying on published specifications. (For example, I just
measured the Z0 of ten "50 ohm" cables of different brands and types
I
have on hand -- it ranged from 44.6 to 56.8 ohms. I already reported
a
loss measurement that was quite different from the spec.)

========================================

The greatest source of divergence between manufacturers'
specifications and what you think you've actually got is due to
manufacturing variation in cable dimensions.


Thanks Roy and Reg,

I understand your point that the calculation engine is more precise
than the model accuracy (against specs), and the product manufacturing
tolerances introduce an even larger error in the predictions. Not
mentioned, but installation and through life degradation introduces
yet another uncertain and possibly greater issue.

Appreciate all the input.

I am sure you are right Roy, this could go on indefinitely. I think I
have gone far enough for the purpose, probably too far, but that is
the cost of confidence that I have gone far enough!

Thanks again.

Owen
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