A $30 DVB-T USB stick just arrived from China and coupled with HDSDR and helpful instructions I'm starting to tune around and hear signals. The first thing I tried was 123MHz AM, air band.
Still lots to learn but this is an encouraging start. These dongles can tune over a wide range, some from 64MHz to 1.7GHz.
Here's a stronger FM signal.
Which DVT-T Stick?
The one I bought was advertised as being compatible. It's hard to figure out from the generic names which is which. This one is simply called "DVB-T STICK" on the packaging. Here is the seller's ad:
There is a list of compatible devices and an active discussion in a subreddit.