Tsukure Preppers [Communication]

In the event of an Alien Invasion or some other global catastrophy it is advisable to be prepared. Tsukure believe knowledge is a persons greatest tool and best of all it weighs nothing, which means you can carry it wherever you go. So picture this, the end of the world is nigh! All hope is lost and you must survive this catastrophe, [INSERT CATASTROPHE HERE].

You need to build some form of communications system to warn approaching friendlys of imminent danger, what do you do?

Simple, find a few old electrical appliances, rip them apart and re-purpose the bits to make a simple FM Transmitter!