On 4 Jul, 08:14, "Richard Fry" wrote:
"art" wrote The antenna from the University is resonant,
tho less efficient than ideal.

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Reprise for Art: The efficiency of an antenna system in radiating the
power available at the antenna end of the transmission line connected to its
feedpoint does not depend on whether or not the radiator itself is naturally
resonant.

It depends on...

1) the ratio of the radiation resistance of the radiating sections of the
antenna to the sum of that radiation resistance with all other r-f
resistances in the antenna system. The pure radiation resistance of an
antenna depends on the effective length//configuration of, and the r-f
current distribution along the conductors exposed to space -- but not those
of any matching devices used in the system design (wherever located).

2) the degree of impedance match existing between the antenna feedpoint and
the source (normally, a transmission line, including any matching network
there).

The DLM uses matching components within the length of a short vertical
radiator with the goals of canceling the high capacitive reactance of this
electrically short radiator, and changing the current distribution along the
radiator for an average value higher than provided by base loading.

So for the same losses in the r-f ground system, the DLM could have somewhat
better system radiation efficiency than a base-loaded monopole of the same
physical height. But good system efficiency would still be heavily
dependent on the quality of the r-f ground used with it (just as in a
"standard" monopole).

This is not a revolutionary concept, as mid- and top-loading techniques have
been used with vertical monopoles for many decades.

RF

The term " cancelling " is not correct tho people seem to be happy
with it.
In fact is it is not CANCELLING anything as it is actually adding to
provide
a state of equilibrium. Big difference
Art