10 June 2016

Unid MSK 1200Bd 800Hz

Yesterday (10 June) morning I spotted this weird signal on 20877.0 KHz/USB at 0725 UTC, unfortunatelly some statics due to a thunder storm ruin the reception.
The signal has a 1200 Hz bandwidth and is characterized by a strong tone at ~1400 Hz (1394) and two simmetical tones at +600 and -600 Hz which are transmitted at lower level than the central one. A sort of "marks" are transmitted each 137.5 ms (pic. 1)

pic. 1

FSK bursts are inserted in a seemingly random way, they have a shift of about 800Hz and manipulation speed of 1200Bd: curiously it's the same value of the bandwidth (pic. 2)

pic. 2
The 137.5ms marks make the period of the signal = 165 bits.

pic. 3