how to find a hidden transmitter placed in a specified area emitting specified frequency using simple circuit?

Question

total area of search is 1 sq km and transmitter emitts 144 to 146 MHz discreet beeps

Answer 1

use an old FM transistor radio with an antenna; stand in the middle of the room tuning the radio to 145 mHz and getting the "beep." Turn the radio and the aerial horizontal and make a slow circle and listen for a raise in the volume. The circuit exists within the radio.

Answer 2

Use an amateur band radio receiver with a Yagi aerial. These are highly directional and will produce the strongest signal when pointed at the source.