I’ve discovered a unique hack with my Samsung Galaxy Note phone.
It was playing an audio podcast and sitting next to an AM/FM clock radio (in AM mode). I tried tuning the radio around just to see what the phones digital interference sounded like.
To my amazement I found I could tune in the audio playing on the phone, very clearly, in multiple places on the dial. Testing with a radio with a digital tuner, I found 855KHz was a good spot.
It works best if the audio level on the phone is quite low and the screen is off. The AM radio makes a nifty audio power amp. Its not perfect, if the charger is plugged in things get really noisy … and when the phone polls the GSM network it makes the radio buzz, as you’d expect if you’ve ever left a digital phone next to a radio.
I’m guessing the phone uses a switchmode audio power amp which happens to make an effective very short range transmitter.