Yes, and here is the answer from the actiontek website
Is the antenna on the Actiontec Wireless Router and Gateway replaceable or upgrade-able? Yes, the antenna can be removed and replaced or upgraded. The connection method is, Reverse Polarity Sub-Miniture Adapter (RP-SMA), is readily available at most computer or electronics stores.
Answers & Comments
Yes, and here is the answer from the actiontek website
Is the antenna on the Actiontec Wireless Router and Gateway replaceable or upgrade-able?
Yes, the antenna can be removed and replaced or upgraded. The connection method is, Reverse Polarity Sub-Miniture Adapter (RP-SMA), is readily available at most computer or electronics stores.