Although they are still heard, there aren’t as many numbers stations around these days compared with the 90s, as they are often transmitted by the same organisations who provide engineering services to national public broadcasters on HF.
A lot of the HF facilities of these broadcasters have been closed down due to the high leccy bills (If you are transmitting 100 kW of RF power, you might need to put in nearly 200 kW of electric power to the transmitter).
As for the broadcast hijacks, for anything affecting a main network transmission its almost certainly the work of a mischevious or disgruntled broadcast engineer. with todays computerised broadcasing, Once you have codes to the playout systems you can insert just about anything you wish into the transmission feed. I nearly “pirated” ICR-FM’s late night show with UTI over Christmas when a corrupt MP3 crashed the planned playout but decided against this as unless authorised by the station manager it would be in breach of their license conditions as its a out of area broadcast (though I have since been told that if the playout crashes again and there is nothing else I can do that, as Ofcom don’t like dead air (silence) either).
