You bought it from someone who's not a dealer, right? If it's used and doesn't work when it's possible that the seller caused the problems, how is it garbage? You would have no idea what it has been connected to (aside from what you were told), whether properly or improperly. It was missing parts and "it's a piece of garbage"? Your logic escapes me.
Those antennas aren't expensive-
The antenna can send and receive wifi in all directions, so no aiming is required. Installation is easy! No software needed. - Frequency: 2.4GHz / 5GHz. If you have any problems, we are very glad to help you.
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