A small transceiver in a wireless security system uses a small square spiral
solid wire (3 turns?) as an antenna. The frequency is 315 MHz, I think.

Most of the remote control transmitters use a 1 transistor LC oscillator that
is turned on and off by a digital pulse stream. The spiral on the circuit
board does double duty as the frequency determining inductance for the
oscillator, and acting as a small loop antenna.


73 Gary N4AST