The external port was a requirement for kits like this https://images-na.ssl-images-amazon.com/images/I/411PQXERG6L._AC_.jpg https://images-na.ssl-images-amazo

The external port was a requirement for kits like this https://images-na.ssl-images-amazon.com/images/I/411PQXERG6L._AC_.jpg https://images-na.ssl-images-amazon.com/images/I/411PQXERG6L... But signal testing kits also used it. This survived until 2G the 5110 still had it. When 3G came out the coverage was good enough and I’m guessing that issues with signal strength in cars was more or less solved.