Much has been written about number stations over the years, although little is known for fact.
We do know they often broadcast on a schedule, so with a little planning, it is quite easy to receive them for yourself. Online SDR receivers take this to a new level, and now with TDoA, we are able to learn something about the geolocation of the transmitters.
It’s probably no surprise to learn many are now being geolocated to the area of Russia and Poland.
I remember the first time I ever stumbled upon a mysterious signal reading out numbers, this was BG (Before Google) so it was hard to identify or read about the history of these stations.
Needless to say, I started to log the station’s frequency and content, and would often find the same stations time and time again.
Priyom.org provide excellent service, collating lots of information in one place. They also link to various SDR around the world, providing you with a unique insight into this mysterious world.
The strange thing is they are still around today, despite us having the internet and 101 ways to encrypt and send messages these days. The attraction of HF is it leaves no digital footprint, and messages can be broadcast to 1 or many recipients over 1,000 of miles.
The Conet Project spent many years recording these strange stations and later selling these as audio recordings on CD’s
You can listen to many of these stations on my SDR, I have been added them to the frequency dial to help identification. Over the coming months, I want to collect some recordings and add them to this page.
Pirate radio stations around 6MHz have been using that part of the spectrum for many years. They often populate that part of the band, and in the main don’t seem to cause the primary users any issues. The primary users sometimes put a STANAG signal on top of the pirate music station, I doubt they even notice the radio station.
The KIWI now has a Time Difference of Arrival function, you can use this to help identify the likely location of an HF transmission.
This evening 6316.5 KHz was active with a music station, and I guessed this may be located in the UK. I selected 3 KIWI receivers located around the SE of England and achieved this fix.
The accuracy can be very good, but much depends on the location of the receivers relative to the transmitter. I repeated this one a few times, and the location did change but always remained in and around Coventry, Solihull area of the West Midlands.
6235 kHz Energy FM (pirate radio relay)
The signal was very strong in the evening, indicating the station was likely to be 100 to 500 KM. The TDoA located it as seen below to Cirencester near Swindon UK.
A further example can be seen in this map, resulted from TDoA Radio Caroline.