The warmup time of the MH Z19b is 3 minutes. So 2 is probably fine, but you could probably do 3 just in case. Although 2 would save your more battery time.
Do you mind explaining your setup a bit more? I would love to do something similar but I do not know where to get started with the PIC microcontroller!
@lis610 I have found with a 499K resistor the range is reduced to about 1.2m in a ABS box.
With a 1Mohm it was about 3m, I do not have many high value SMD resistors to experiment with but the lower the value the lower the range.
Just tried with a 333K and it operates about 0.8m in free air.
@The-Grue: Don't be embarrassed by it...pretty sure you are not the first one that fell for this trap and certainly not the last one. Hopefully also other readers on the forum can benefit from your (bad) experience in this way.
Thanks for reporting back and good to hear that some of your trust has returned towards the nrf24 and your part shops with a "good name" .