Failure to receive the corrected Preamble

[Hamid Rahatloo]

HI
I'm using a USRP to receive a signal on the 900 MHz frequency band, but the
signal received after demodulation has no preamble. Does anyone know what
the cause is?
transmitter information:
Baud rate=10K
modulation = BFSK
deviation = 100K
channel spacing = 350K