Roelof,
I remember reading about a very similar antenna arrangement early in my
career. It was described by the writer (name forgotten) as "one plate of
a capacitor - the other plate being the rest of the universe". Somehow
that description has stuck in my mind and has served to provide a simple
explanation of "small" antennas in general.
73
On 04/07/13 13:37, Roelof Bakker wrote:
Hello Stefan,
I have been reading VK1OD's article with great interest.
It is a pity that he has not discussed the antenna with yours truly.
This should have avoided a number of inaccuracies.
I have had quite a few email exchanges with a number of experts.
Some state that the antenna can't work, others said that it works, but
that I did not understand how it works.
Which was true!
The antenna has evolved completely by experimental work with the goal
to find an antenna that will work on LF and features immunity to in
house local noise. Which goal has been achieved.
To understand how it works requires a bit of up side down thinking
(literally!)
The antenna emulates a monopole, however what we consider to be the
antenna element, it is not.
This applies also to the classic active whip, at least on LW and MW.
In fact, the antenna element should be considered as an artificial
ground and that is the reason that e.g. a 1 meter long whip can be
replaced by a piece of copper clad PCB with about the same capacitance.
There is no question that this concept works. I received NDB IPA-280
from Easter Island in the Pacific on it.
And no weak trace screen watching whatsoever, but aural copy of the ID
in morse code.
It should be nice if all members of the amateur community were well
off and could afford unlimited real estate.
In that case we all should be using beverage farms for reception and
spending a bit more time in the great outdoors to keep things up and
running.
However the vast majority will have to cope with limited resources,
being lack of real estate, lack of finances or both. This is where a
bit of ingenuity comes into play and the fun starts.
It is truly amazing what ideas have been put to work to overcome
unsurmountable limitations. One excellent example is the ongoing
development of weak signal software, which has made LF work possible
for many more people than just the happy few!
Best regards,
Roelof Bakker, pa0rdt
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