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Re: Terry's New Plane Wave Antenna
Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
Hi,
At 09:11 AM 12/22/2005, you wrote:
Hello Terry,
I still don`t understand some things about this antenna. What is the
purpose of the "ground
plane"? See - the first case: if we use not the etched board (simply
a piece of PCB) and the ground
plane - the first (sensing) plane will just shield the back one -
the ground plane! And the ground
plane seems to be useless.
The separated plane was originally so the secondary C2 in the divider
could be very small. It also help make the thing directional. But
these reasons may not be important.
The second case: we use the etched one. Here the ground plane serves
to stop the field lines of
force at itself, right?
The etched pattern is to fight eddy currents. However, since the
frequencies are pretty low, you could probably use a solid plane just fine.
And as for the capacitance divider - it has 2 caps:
the first one - the capacitance between the toroid and the "sensing" plane,
the second - 16nF (that should be choosed for best calibration).
You see - we don`t need the ground plane again, coz it doesn`t
serves as a capacitor plate for that
divider.
The 16nF is not critical at all. for the size, that value works out
well though.
Have you tried to use your antennas without the ground planes?
Until you all started talking of this, I really never thought about
it. The antenna's present form is really "just the way it turned
out". I see no reason why you could not use a solid sheet. The
present etch pattern and back plane structure does have advantages at
very high frequencies, but that may not be an issue at all for most work.
Cheers,
Terry
Best regards,
Grishka mailto:ghome@xxxxxxxxx