My story is set in an apocalyptic Earth (occurring during the story), and the main character is stationed out alone on a sea fort in the middle of the ocean.
He receives a radio call/signal from a stranger on his radio (or something similar). I don't know enough about radio waves to know if this is plausible - could an SOS call show up on a radio like this? It's basically a voice in the wilderness - someone sending a one-way message out, hoping someone will receive it.
Further, is there a plausible way by which he might 'fix' the device he uses so that he could be able to send a signal out back to the recipient, but that doing so would then permanently prevent him from receiving a signal again?
I'm open to new technology (or old rediscovered tech) being used, as well as interference/jamming being caused by the environmental effects of the fall of civilisation around him.
Thanks so much - the downside of my only studying arts/humanities is a real lacuna in my knowledge of science and physics!
EDIT: So, a crucial plot point is that the main character essentially sacrifices his ability to receive transmissions in order to attempt to find a way to transmit back to the broadcaster. It's essentially an act of love and sacrifice, whereby he gives up the consolation and hope that receiving the messages gives him, in order to instead gives those things to the woman whose voice he hears. Therefore, it's crucial that a) the 'fix' to his radio means it can't receive messages anymore and b) the fix could conceivably allow him to transmit long-term. It wouldn't be worth it if he could only send one message, as with the battery/satellite phone idea below.