Not vouching for "degree of accuracy", but here's how I estimate efficiency:

(Known Rrad/Measured R at X=0) at the feedpoint.

If my Inverted L has a predicted Rrad of 25.9 ohms and I measure the R at
resonance as 29 ohms, the 3.1 ohms is return loss. This would indicate an
approximate efficiency of 89%.

It seems to me to be a fair approximation. When you have added as many
radials as possible and watched the input R at the feedpoint (at resonance)
drop asymptotically toward the predicted or "known" Rrad, your final "R"
value is used in: Rrad/R. For a perfect ground Rrad = R

I use an MFJ-269 antenna analyzer for the measurements.

Have I gone astray? (aside from my starting value of Rrad, which I took from
two sources: your rule of thumb formula for Inverted L's, and ON4UN's Low
Band DX'ing Handbook). Both your formula and ON4UN agree as to the value of
Rrad for my antenna.

I'll replay to other aspects of your response in another post.

73 and thanks for the new program. As you can tell, I've been playing with
it. As you can also tell, the implications with respect to length of radials
required for good efficiency are causing my brain to cramp.

....hasan, N0AN

"Reg Edwards" wrote in message
...

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Yes Hasan, good agreement. How did you determine efficiency to THAT
degree of accuracy?
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