I thought the connect was on top, it is on my units. It is a standard board level connector used on lots of boards to get to the connector on the case, and Seeed sells 2 antennas with it, or a u.fl to sma adapter. A lot of laptops use this same connector on the built in wifi cards, and it is used on a lot of other gear I have. It is not easy to find, deliberately in the USA, to meet the FCC rules on non-standard connectors for antennas for type acceptance. (There are some arcane rules about radios with “standard” antenna connectors vers. custom antenna connections that are non-standard and as such users can not arbitrarily add higher gain antennas and exceed power limits on part-15 and other type acceptance rules on transmitters. Basicly the rules are strict, but are falling apart because people want stronger wifi transmitters. The regulators hate devices that can not be proven to stay within limits. One way to comply with the rules is to use a custom non standard connector to prevent the average user from changing things. For a gps it does not matter, but this is used of lots of RF gear. If you could easily but it they could not use it.)