prestonkavanagh
Joined: 27 Nov 2018
Posts: 16
Location: Tarpon Springs
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 Posted: Fri Jul 17, 2020 12:49 pm Post subject: ground planes - new source for copper foil and questions |
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I have been working on a transponder antenna for a fiberglass airplane (Cozy IV). I tried thin copper sheet, then copper flashing. I hated the weight of the first one I built (and the Frankenstein look of the riveted, soldered seam), the second one was better and on the 3rd try I got a keeper. The reason is a new super thin copper foil. $14 bought 10 sheets, enough to make multiple transponder antennae. See
https://www.amazon.com/gp/product/B07R8BS843/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
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?
Thanks for the help. PK
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PBK3
PA-12, BD-4, RV6a, gliders, Rutan canards |
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