Yes, you need to have an antenna. Ham radioes operate in HF, VHF and UHF frequencies. There are particular civilian bands within these frequency ranges. The HF band is the only one that allows long range communications beyond line of sight, unless you have a relay tower for VHF and UHF. Some States have Ham operated relay towers that span the entire State and allow Statewide communications via VHF and UHF. HF simply needs an antenna and with the right frequency, you can communicate with anyone else with an HF radio anywhere in the world. Choosing the right band to communicate isn't terribly difficult. Using your receiver to listen to the different bands will tell you which band is operating long-haul. The more traffic you hear in a band is where the propagation is. You simply choose a frequency within that band and know that your signal is travelling long-haul. Whether you can communicate with a specific targets location is a bit trickier, but this is why we practice HF.