SX1268 frequency setting

Hello, I am studying the frequency range on which 1268 can work, and I came across a problem, it does not start at a frequency above 710 MHz. And then in the region of 660+ there is already a large drop in power (I evaluate it with a spectrum analyzer). The range that I got is from 410MHz to 710MHz, although the documentation says from 410 to 810MHz. Why can’t I get 710+? I calibrate the image using the sx126x_cal_img_in_mhz(NULL, freq-5, freq+5) function from the library sx126x.

What does image calibration affect? I checked on 1262, the output power is the same with any image calibration.

Maybe I am calibrating the image incorrectly? Which calibration algorithm is correct? I have this:
STDBY mode,
calibrate image,
set frequency,