CC1101 continuous RX calibration time?

If you don't calibrate when you change frequencies by more than 2MHz, you will get frequency offsets which will make it difficult to impossible for the receiving radio to lock onto the transmitted signal (assuming the transmitted signal was calibrated so it is at correct frequency).  One thing you can do is to run through your calibrations during initializations and save the FSCALx register values in an array for all of your channels.  Then when you want to switch channels, just load in the new FSCALx register values.  See sections 19.6.2 and 28.2 of the CC1101 spec sheet (http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=cc1101&fileType=pdf).

Using the above described method, you can change frequencies much quicker than calibrating each time.  Note that the calibration values will not be valid if you have severe temperature changes of the part.  As long as you stay in RX mode, you shouldn't need to re-calibrate after each reception.  If you cannot monitor the temperature of your system you may want to run calibration manually every 10 to 20 seconds or so, that way you will manage temperature effects.

Jim Noxon