For the past several years, I have been hearing odd transmissions on 6914 kHz in AM mode. For lack of a better name, I’ve referred to this as the 6914 Oddity. I’ve heard a mix of cryptic voice transmissions, as well as MCW (morse code transmitted with an AM carrier) as well as RTTY and some MFSK digital mode, all transmitted in AM, not SSB as is typical with these modes.
The station will have a burst of activity, lasting for several days, then go silent for a period of time, weeks or even months.
Based on the times I can hear the station, and signal strengths, it seems to be something on the order of 500 to perhaps 1,000 miles from my location (Maryland). That could place it somewhere in the northern and eastern USA, or perhaps southern and eastern Canada.
I regularly run overnight and weekend SDR recordings from 6800 to 7000 kHz to catch any pirate stations that may be on, so these transmissions routinely show up in the recordings.
I observed the following voice transmissions last night (UTC 13 September 2015) on my regular overnight SDR recording:
At 1206 a transmission was made in an MFSK mode:
This was followed at 1215 with an RTTY transmission. The signal was too weak to decode, but previously 50 baud and 1000 Hz shift was used, with a center frequency of 1700 Hz:
There has been some speculation about the purpose of these transmissions. One thought is that they are SIGINT (signal intelligence) training exercises. But for now, the true purpose remains a mystery.