The requirements for a working antenna are actually pretty loose-- In most cases the TV will have two RCA jack inputs; one for cable and one for an antenna but

The requirements for a working antenna are actually pretty loose-- In most cases the TV will have two RCA jack inputs; one for cable and one for an antenna but the coax cable that goes from the wall to the TV will generally work just fine as an antenna if you plug it into the antenna jack and remove it from the wall so just the cord hangs off the back of your TV. If you are in an optimal RF location (within a mile or two of the transmitter, no major obstructions, low noise floor, clear conditions etc) it should generally be possible to pick up OTA signals without any antenna at all.