butterfly capacitor is the best option for the magnetic
capacitors are hard to find, expensive but they can be
start this project with some hand made drawings that was
photographed and transferred to the PAINT BRUSH.
PAINT BRUSH drawing can be seen on the left top of the
above figure, this technique gives me the freedom to test
designs of the fixed and the moving plates and select
the appropriated hardware.
are two basic parameters to design a variable air capacitor:
1) Plate’s area
2) Distance between plates.
voltage capacitors needs more spaced plates to avoid arching,
at QRP levels the plates can be closer from each other
resulting on more compact designs.
is a very usefull program written by KI6GD called Capacitor
Calculator. It works very well to me in designing all
kind of variable capacitors.
page label sheet printed ready to be applied to the aluminum
final drawing was a 4.5 centimeters by side square copied
12 times filling
3 colons and 4 rows.
This figure was printed on a full page size label to be
applied directly over the
aluminum 0, 5 centimeters foil.
with a metal scissor
the points to be drilled
foil with drilled holes
above photos shows the 12 squares drilled
next step is carefully cut the crossed lines with a DREMEL
off the guide drawings on the printed label sheet over
the pieces and start to work on the plates to make them
polished and as plain as possible.
the butterfly capacitor plates
mounted capacitor plates
and back acrylic parts
my model I have used some thin washers between the inner
face of acrylic front and back mounting pieces and the
extreme nuts on the screw used to avoid mechanical instability.
procedure is needed to an appropriate free aisle movement
keeping it firmly like the professional units.
PY1 AHD ALEX (Alexandre Grimberg).