No preamble Sequence, but it works

I tried to see the preamble sequence and Start of frame delimiter (SFD) in my Spectrum analyser (RSA 306B), however there is no synchronization Header (SHD) in any Xbee package.

I can easily see the OQPSK modulation, but it not respects the Symbol to Chip Mapping (2450MHz)

Both Xbee are communicating perfectly. When the light is too bright or too dark in the photoresistor in my bedroom, the arduino transmits to the Xbee module. This Xbee transmits to other Xbee module, which turns the LED on.

What´s happening? Can someone show me a pic of real Xbee signal, specifically, the SHD part?

I´m using Xbee 2mW U.Fl Connection Serie 2. Both Xbee are using the channel 20 (2450 MHz).