OMP4
OMP4 (Arvorian: ОМП4), also known by the nickname "The Polytone", is a shortwave radio station based out of the Arvorian Democratic Republic transmitting on the frequency 3828 kHz. It broadcasts a short, modulated polytone sequence which repeats at a rate of approximately 35 tones per minute, 24 hours per day. Occasionally, the signal is interrupted for unknown reasons, and on occasion a voice transmission in Arvorian takes place. The station is allegedly reported to have started broadcasting in 7672 RH and is believed to be connected to the Armed Forces of Arvor.
Format
Unlike ANVF, OMP4 very rarely broadcasts voice messages. To date, listeners have noted only fifteen voice messages being sent out. On those rare occasions when it does, they follow the same "Monolith code" format used by ANVF. The one distinct difference lies in the way the station is identified - instead of a repeat of the callsign at the beginning of the messages, it is read at the beginning and end of them.
Location and function
As with the OMP4's sister station, ANVF, the Arvorian government has never officially acknowledged its existence. Shortwave radio enthusiasts have loosely pinpointed OMP4's source to a transmitting station on Kamenskoye, in the Southern Islands. While the station is known primarily for the distinctive tone which it broadcasts all hours of the day, those who keep a loose monitor on the station have noted that the signal has been interrupted precisely seven times since the station first went active, for periods ranging from thirty minutes to as long as twelve hours, though for reasons unknown. A variety of theories have been posited as the cause of the interruptions, including everything from scheduled nuclear tests to specific military drills conducted on the island or in nearby waters to atmospheric testing. The station's connection to the military is considered likely to be fact as the island is closed off to non-military traffic and known as the site of a weapons testing range that has been in operation since 7608 RH. As of current date, no indications of secondary transmission sites, active or otherwise, have been found.