Oz, here's one for ya. The airways beacon here used to transmit on freq 251 kc - they just kept the old radio range freq when the range was de-comissioned. Along about the mid 70's, we began to notice interference on the frequency. Some nights, you could actually hear weird music for short periods, and the RMI needles would head off to the east. After a few complaints by us and a few other operators, one night a radio tech from Transport Canada did a jump seat trip with us to see for himself. The reception was really great, and you could even hear the announcer, as well as the music. They NOTAMed the beacon as unreliable, subject to unknown interference. About a month later, they discovered the culprit. Bangaladesh had gained its independance a short time earlier, and not being a member of ICAO, they were using frequencies below the AM band for broadcast radio purposes. Turns out what we were hearing on 251 kc was the Bangaladeshi hit parade. The output of that station was something like 200,000 watts. They changed our freq to 273 kc and got rid of the problem.