The best replacement for external antenna is internal antenna.

The best alternatives to external antenna are rated as following:
★★★★★  internal antenna
★★★  internal router

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Speaking about external antenna, one probably shouldn't forget about usb modem.

Other search terms related to external antenna and their ratings are:
★★★★★ usb modem
You have in mind a companion for external antenna and it is not yet here? Propose!



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external antenna
internal antenna
internal router