Ian White, G3SEK wrote:
Where you're going astray (I suspect) is in believing that the coil
literally "replaces" the 45deg of antenna that was lost when we halved
the height. It doesn't - the loading coil drastically changes the
current distribution.

No, I do NOT claim that the coil literally replaces the 45 degree of
antenna that was lost. The feedpoint impedance drops which indicates
that it is not a literal replacement. The decrease in the feedpoint
impedance indicates that the antenna is not radiating as much energy
in one cycle as a full 1/4WL vertical since the reflected current has
increased. This is consistent with field strength tests.

Since we have assumed a lumped loading coil, the current at the top of
the coil is the same 0.9A. But now the current distribution in the top
22.5deg is very different from the full-size case: it tapers much more
sharply, from 0.9A down to zero at the very top.

I propose that it cannot do that. Seems to me, the impedance looking toward
the end of the antenna is approximately the same for a six foot whip Vs the
base of a six foot whip mounted atop a coil. I don't see any reason to suspect
otherwise. Please provide me a reason.

the feed impedance of the
loaded antenna is much lower than that of the full-size;

.... which proves my point above. That indicates that it is not as efficient
a radiator as a full size 1/4WL vertical. In fact, the less efficient it
becomes as a radiator, the lower the feedpoint impedance. This fits in
exactly with the fact that a good 75m mobile antenna has a ~12 ohm
feedpoint impedance.

To sum up, shortening and loading the antenna creates so many important
differences that you're misleading *yourself* if you say that the
loading coil simply "replaces" the missing length of antenna.

I never said that so I assume that is your straw man. If that is not
a straw man, I apologize but it walks and talks like a straw man.

1. The diagram for current distribution with center loading in 'Low Band
DXing' is based on the same incorrect assumption that loading coil
somehow fully "replaces" the missing 45deg of antenna.

Please prove that a shortened antenna that is electrically 90 degrees
doesn't replace the missing number of degrees in the physical antenna.

2. I haven't thought about an answer to Cecil's problems of what happens
to the "missing" 45deg, and what happens to the forward and reflected
waves of voltage and current.

That's more than obvious, Ian. :-) How about thinking about those nagging
questions and providing us an answer? This is what happens when one ignores
the basics. The steady-state shortcut strikes again.

My only point is that a correct solution can *not* involve a difference
in the currents at the two ends of an idealized lumped inductor. Such a
difference simply cannot be... so the true solution will be that bit
harder for Cecil to find.

Since there is no such thing in reality as an idealized lumped inductor,
there is no real solution to the problem. Please allow me to suggest that
you guys are just engaging in mental masturbation. Was it good for you? :-)
--
73, Cecil http://www.qsl.net/w5dxp



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