Here are a couple of examples of numbers stations (Both recorded today – 29th October 2017).
The First, which has been broadcasting since about 1973 is one nicknamed “The Buzzer” for obvious reasons. It can be heard on 4625KHz. It has been know to transmit voice as well as the distinctive buzzer sound. No one knows what its for.
The next one is a better example of why they are known as numbers stations. This one is Polish and doesn’t transmit all the time, but when it does it sends a coded message like this one I recorded this evening on 8102KHz, it went on for about 3 mins before stopping – I missed the beginning of the transmission as I forgot to put the SD Card back in the radio.
I will add more to this post as I find them.