Sub 1GHz tuning ranges

[drom]

Great project!

I was wondering if you tested Sub-1GHz tuning ranges for Tx and Rx?
Is there a sharp limits to 389.5-510 MHz / 779-1020 MHz ?
Is it PLL lock issue? or dividers?

[matteoserva]

The documentation for the modem at86rf215 only states that

The frequencies must be within the supported range, otherwise the behavior is undefined. The device is not protected
against incorrect frequency settings

From the datasheet i don't see anything preventing me from putting arbitrary values in the register containing the center frequency.

The cariboulite library, cariboulite_radio.c, performs an additional check on the requested frequencies and blocks values outside the allowed range.

[drom]

What is I am explicitly interested in values outside of the range?
Anybody did experiments in the LAB?

[matteoserva]

I expect the internal PLL to not lock outside its range.
Do you have a specific use case in mind? Why don't you use the wideband channel and avoid that limitation?