Best is a Flightaware 978 Mhz antenna:
Professional, high gain, impedance matched, sturdy and suitable for indoor/outdoor installation, and above all, at a very competetive price.
However if you want to have fun with DIY, here are two $1 DIY antennas:
Cantenna
Quick Spider
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@wiedehopf
Did you ever try a Cantenna?
It is a wide-body “koaxialantenne” (coaxial dipole). Due to large dia of coke can instead of a narrow copper pipe, it performs much better than original koaxialantenne design. The added advantage of using coke can instead of a narrow copper pipe is that a groundplane disk (bottom of the can) is added.
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(Translation in English in red color added by me)