What is the nRF51822 intermediate frequency?

[steriana]

Our FCC test house is asking what the IF frequency is for the nRF51822

[ketiljo]

The IF is the difference between the receiving frequency and the LO. The LO is at (fRX+2MHz)*8/7. This gives:

fIF = fLO - fRX = (fRX + 2MHz)*8/7 - fRX = 1/7 fRX + 16/7

So at channel 2400MHz, the IF will be at 345.143MHz and at channel 2480MHz, the IF is at 356.571MHz.