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At the experiments I used several homemade GDO. Reference 7
shows several schematic of the GDO that may be used to find
the resonance frequency of the helical antenna. Some of
them were repeated by me. As well I used a commercial made
GDO that was made in the USSR. The GDO brand name was very
simple- GDO.
It was made for amateurs in a military plant. The GDO was
really good.
Later, in the article you will found sentence: When
the
helical antenna is tuned to the resonance frequency it should be measured the antenna input
impedance. Modern amateurs who tune the antenna with modern
devices like MFJ, VNA and RigExpert
cannot understand the words, because the devices already
show the input impedance. But in the far dark times I tune
the antenna to the resonance with GDO- the reason was very
simple and pure: the GDO was light in weight, reliable,
and shows the resonance frequency of the antenna in a wide
range. That is all what I need. Only when antenna was tuned
to the resonance I did measurement the input impedance with
RF- Bridge plus feeding the Bridge RF- Generator... A little
bulky equipment.. However, now the life is significant easy.
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Picture 8
Soviet GDO- Simple GDO
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