nuckolls.bob(at)aeroelect
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 Posted: Fri Jul 17, 2020 1:38 pm Post subject: ground planes - new source for copper foil and questions |
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| Quote: | The foil comes with a conductive adhesive backing, so I don't have to rivet and solder. The following were consistent measurements:
- internal resistance, multi-meter: 0.4 ohm
- resistance across face of sheet: 0.4 ohm
- resistance from face of sheet and across adhesive: 0.5 ohm
A package with 10 sheets weighs 201 grams, for weight per sheet of 20 grams (less than an ounce). The sheet size is 300 mm x 200 mm (11.81" x 1.87").
Are there optimal / resonant shapes and sizes for the ground plane? The bible calls for a circle with 5.5" diameter (p. 13-2). I can fit an 11" circle under the co-pilot seat of the Cozy. Stick with 5.5"?. And I believe I need a second, mirror image install for the ADSB. Is that right? |
Yes . . . there are 'tuned' ground planes 1/4
wave radius around the base of the antenna.
That's were the 5.5" figure comes from . . .
it's 1/2 the height of the XPNDR antenna.
Be cautious of thin copper foils. Copper,
like aluminum, is a non-ferrous material with
a service life under bending vibrations
and other external forces. Stay with 5.5"
o.d. and consider something more robust like
0.040 aluminum disk.
Had a builder fabricate a comm dipole
on the inside surface of a fiberglas
tail many years back. Used copper foil
bonded to inside of structural shell.
A few years of stress cycles due to
temperature coefficient of expansion
of two materials developed cracks in
the elements.
The solid aluminum disk can simply lay on
the inside of the skin like a big
washer . . . works good, lasts a long time.
Bob . . .
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