After some test with SSB reception I found what frequency output tends to drift around 3-5 Hz, it sems to be not syntezer.. I tryed TCXO - same results. If I touch chip with something magnetic I can listen big frequency shift (but it return back after some seconds). Is it possible to use external heterodyne with this chip (not TCXO to RCLK - it will not help)
It doesn't have the PLL inside. It only has the AFC locked to crystal (RCLK), like the FLL.
Mixing down the RF signal externally is also not workable for Si4735