9
Tho coupling was used for IF circuitry in the late thirties to
achieve
high Q it was more than 40 years before coupling made an appearance on
a macro
scale on the transmission side. On warships it obviously essential
that transmission were clean but on large ships there were many
structures that would reradiate a signal using energy from a
transmitter. It was found that if a loop was placed near such
structures energy would pass between the structure
and the loop circuit via back EMF such that via coupling the now
parallel circuit would move the offending signal( See ARRL
antenna/handbook)
..Around this time the loop anteena made an appearance where a short
element was end fed an placed close to a loop containing a capacitor.
Again EMF was at work where two frequencies could be made one and
where a slight change in the loop curcuit allowed the combined
frequency to be moved.
At the same time Moxon introduced what was called the disappearing
inductance
(antennas for all locations) where he fed a normal dipole instead of a
short member as in a loop antenna and placed it in close proximity to
a loop circuit.
In this case tight coupling was required for a single frequency
emmision such that the loop
became a physical part of the dipole even tho two circuits remained.
Again the capacitor in the loop allowed resonant transmissions over
at least an octave Art took this further by close coupling more loop
dipole elements in yagi beam form. Art became more interested in the
single element form because the combination loop dipole could supplant
the traditional trapped dipole but with the realisation that more gain
could be attained because the radiation was of collinear form and thus
looked for different ways of feeding the dipole combination instead of
a delta feed.
It was at this point that Art
made the loop in ladder form since frequency span depended on the
loops periphary as well as changing the feed to one of a coupled
circuit form.
More to come but special thanks to the earlier posters who added more
insight
to the values of Q.
Let the attack commence
Art
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