Gene Fuller wrote:
Do you s'pose that if the equality is perfect for zero-loss lines then
maybe it is an useful approximation for low-loss lines?

Do you really think R&W were proposing that this simple relationship is
more appropriate for low loss lines than for zero loss lines?

Nope, exactly the opposite. Apparently, they were proposing that this
simple relationship doesn't hold for highly lossy lines. Chipman also
has something to say about highly lossy lines.
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73, Cecil http://www.qsl.net/w5dxp