If your smartphone provides some FM radio function but you've ended up losing your earphones, your kind of out of luck until you buy a new pair. Unless your smartphone happens to be an Xperia, which can now be modified a bit to make the seemingly impossible happen.
Most of the smartphones these days that have offer FM radio require you to have your earphones plugged in before they can function. The reason for this is that the phone uses the earphones as antennas to receive radio signals. Some might find this requirement quite limiting and would not like to remain beholden to the wired buds. Thanks to a tutorial from XDA, they might no longer have to.
The downside is that the process requires a bit of technical knowledge that might scare off majority of users. Luckily, there are said to be many tutorials around the Internet that carefully guide on the arcane art of using smali, the assembler/disassembler tool employed in this Xperia trick. In a nutshell, users will have to search for the Radio3.apk (Android package), decompile it, edit the PhfHandler.smali file that gets generated, and then recompile it again into Radio3.apk for pushing back to the device. Should you manage to survive that ordeal, you may now listen to your favorite FM stations without having to wrestle with tangled headsets.
Given the rather involved process, some users might just opt to buy another pair of earphones to satiate their needs. The difference in audio quality or signal reception is still unknown at this point. This method does have the advantage that you are no longer confined to keeping that song to yourself but can now play it out loud if you wish, in the right context, of course.