wireless - How can I tell if an RF transmitter is transmitting?

In my project, I use a use an RF Transmitter and Receiver. One of the RF components seemed to fail because the connection between my Arduinos no longer works. I cannot determine whether the RF Receiver or Transmitter works. I want to see if my RF Transmitter gives an output, but I do not own an oscilloscope to view it's waves. I've seen this answer, but it only shows if the Arduino is sending data to the RF Transmitter. Is there any alternative way to check if the RF Transmitter works or not? Thanks!