W6WRT writes:
> A GDO "deceptive". I could not disagree more. Assuming the GDO is
> designed properly, what is says is happening really is.
Since a GDO is a hardware device, it cannot be deceptive. However,
the results obtained by using a dip meter can certainly be deceptive
because what is displayed is not always what the user THINKS is being
displayed.
Take a simple parallel resonant circuit - an antenna trap. Suspend it
between two strings several feet from any other surface and you have
a relatively reliable indication of the resonant frequency of the
trap. Place that trap on a counter and the dip may no longer occur
at the resonant frequency of the trap ... who knows if the counter top
has metallic inserts, edges, pigments, etc. Replace the strings and
suspend the trap with wires ... now what does the dip indicate? Is
it the resonant frequency of the trap, the resonant frequency of the
"antenna" formed by the wires and trap, or the loaded frequency of
the "trap?"
Similarly, couple a dip meter to one grid lead of a 3-500Z. What
does that dip tell you? Is it the frequency at which the grid is
the most effective shield, the frequency at which it is the least
effective as a shield, the frequency at which the grid lead and
G-P capacitance resonate, the frequency at which the loop formed
by the multiple grid leads and bypass caps resonate? What is really
being measured?
Quite simply, the dip meter does not tell you what is really being
measured. Unless the measurement is of two high quality components
in total isolation, anyone who reports dipmeter test results without
accurately reporting the test conditions is being deceptive.
73,
... Joe, W4TV
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