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ERRANTE's HF Turnstile
antenna broadband driver : what it is, how it works and what it
does.
by Francesco Errante
The Errante's Turnstile antenna driver, is a broadband
radioelectric circuit based on our own original virtual ground balun design.
A turnstile antenna, which is also known as cross-dipole or
quadripole is the top choice when a quasi-omnidirectional radiation pattern is
requided in a horizontally polarized antenna system.
When it comes to point to point and broadcast radiocommunications through the
ionospheric radio-propagation, such systems have the advantage of following the
wanted signals, no matter what changes in the direction of propagation the sky
makes.
Trans-ionospheric effects include refraction, amplitude and phase scintillation,
signal delay and polarisation rotation. Such changes always affect the strength of
the wanted signal during ionospheric radio propagation reception (QSB) and can easily
reach a 20 dB loss. A turnstile antenna system driven by this device of ours
will recover that loss and on average all signals are 10 to 15 dB higher compared to
what a single dipole would extract in the same conditions.
Untill now, making a proper turnstile antenna for the short wave bands used to be a
mammuth task and no previous system could allow multiband operation owing to their
own delay line limitation.
The device presented hereby is, instead, the ideal solutions to manage a cross dipole
as you would do with a single one. It, infact, exhibits the same properties as our
own virtual ground balun, while making easy to drive 2 identical dipoles or 2
identical fan dipoles in a turnstile configuration, thanks to its unique
phasing system. By eliminating the need for a delay line, our system also eliminates
all the loss of signal that inevitably comes with it, therefore, the quantity of
energy tranferred to each of the 2 dipoles is precisely the same, this will translate
in a truly symmetrical radiation patten.
Where fan-dipoles cannot be used through lack of space, multiband operations can
also be achived by employing trapped dipole branches.
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