This antenna looks like a simple 2.15dBi dipole antenna. I used this to add an external antenna to a Raspberry Pi that was being moved in a metal case (I'm a licensed hobbyist working as part of a ham radio station). This antenna achieves about 4-6 dB gain compared to an antenna in a metal case, which should be well below negative dBi values. In addition, it is VERY sensitive to position and nearby objects. For example, I can't attach it to the case or my signal drops by about 20dB and I have to orient it so that the "top" of the antenna is facing my access point, as any other orientation will result in a bad signal.
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