Software Radio Transmitter
SDR (Software Defined Radio) is allows receiving radio signals over a wide range of frequencies and allows directly importing into a computer for processing.
Listen to FM radio, Air traffic control, GPS signals, Police/Fire/Ambulance (if your area still uses unencrypted radio)
BUT cheap receivers don’t allow transmitting, it costs over $400 for transmission capabilities, which moves it out of the realm of hobbies.
Transmitting can be accomplished via a USB to VGA adapter with a Fresco Logic FL2000 chipset. $15us. Complications; to transmit GPS coordinates requires you to pre-create a 40GB file that you can play-back