Why does a phone's flight mode also disable FM radio? I had two phones being capable of listening to VHF FM radio (in Germany about 90 to 104 MHz).
However when turning on flight mode, the radio receiver is also disabled, and I wonder why:
Listening to radio does not transmit any electromagnetic waves (more than when playing some game I guess).
I thought it would be some fun listening to the different radio stations while passing countries from above.
All broadcast-band radio receivers contain local oscillators which are used in their intermediate frequency (IF) circuits to downconvert the (higher) frequencies they receive. These IF circuits are prohibited by law from radiating more than very small amounts of radio frequency power while operating, but to prevent any possible chance of having the airplane's navigation receivers pick up interference from portable radios, they have to be shut off during flight.
This is a minor problem today, but old-school shipboard radio receivers during WWII were supposedly capable of radiating enough power off their IF stages that submarines could tune in on them and use them as homing beacons to track convoys and then sink them.