Who's your Internet provider?
Speedtest.net will tell you the download/upload speed for what you're getting.
Anything above 5Mbps is decent, but Comcast is rated around 15-20Mbps download speeds, or faster if you pay more.
I'm not sure I understand what you mean by "radio signal from a tower".
If you're paying for Internet service, they should give you an indication of what kind of speed your service should be rated at.