We should get the idea "less BW indicates more efficiency" out of our minds.
I think I see why you said what you did, Tom. If we replace the two
elevated radials under our inverted-L with an FCP, and the bandwidth gets
a
little narrower, then yes, that doesn't prove that we've improved the
efficiency. Only FS measurements will, unless I've forgotten something
(again).
Bandwidth is a complex function of the reactances and the resistances in the
system. The ONLY case where less bandwidth would indicate less loss would be
where reactances all through the system and radiation resistance,l
normalized to one place in the system, do not change. If the single variable
in the system is loss resistance, and there are no transmission line effects
involved, we could see the trend match.
There are probably many more cases where bandwidth means nothing with regard
to efficiency, or goes the wrong way, than it goes the way we "think".
In most cases on this reflector, an earth radial system is being
discussed,
and the quoted statement made to me off-list is generally true. But you
knew that. :-)
It might be true in that case with one specific unchanged antenna system. It
might not.
I thought I remembered reading a comparison between what I have (a 155'
inverted-L with the vertical portion 55' high and two 10' high 1/4 wave
radials) and someone who replaced their radials with an FCP. I remember
thinking that the resulting reduced bandwidth is too narrow for my
interests.
If we replaced a ground system with a small whip and low-loss loading coil,
bandwidth would become very narrow. Feedpoint resistance might go down also,
I know it does in some real cases that I have measured.
At the same time, with lower feedpoint resistance and much less bandwidth,
we have more loss.
We really should move beyond not measuring what we want to know in any
meaningful way, and making a claim based on complete nonsense. To this date,
as far as I know, no one has measured relative efficiency. More important,
it does not model as an improvement. Without measuring FS change we just
have meaningless suppositions.
73 Tom
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Topband Reflector
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