surfboard cable modem sb5120

Can i plug a wifi aerial into my broadband modem?

and maybe get free broadband off someone elses connection on my street? My modem is a Motorola SURFboard® Cable Modem SB5120, http://broadband.motorola.com/consumers/products/sb5120/

You can only plug an aerial into a Wireless Router in order to improve a wireless signal that already exists.

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