Hearing broadcast FM at 31.1 MHz with an SDR
I'm brand new to radio, software defined or otherwise, so forgive me if this is a particularly stupid question. While listening with my RTL-SDR dongles, one E4000-based and the other an R820T, I can hear broadcast FM on 31.1. The station I hear on that frequency is 106.7, and both dongles pick it up. It's not the only FM station I can hear on frequencies too low for ordinary, broadcast FM. Why would I be hearing those there? Before I tried it with the R820T, I thought it must be an artifact of the SDR, since the E4000 can't go below 50 MHz, but they both pick up the same signal at the same frequencies, so I'm assuming it's really there.