NRF51822 Frequency Error

[Elliott Makin]

I have some units that seem to have a frequency error.

Please see image below from a spectrum analyser. It is the received signal from 2 units both transmitting a constant carrier on channel 10.

The peak on the left is a little low - 0.8mHz The peak on the right is way of +33MHz

Do you have any idea what can be causing the frequency error?

Replacing the crystal and loading caps has no effect on the frequency.

Amazingly these units still operate quite well with the Gazelle protocol.

[AmbystomaLabs]

I would guess that you are running the test to measure channel accuracy with some custom code and have failed to invoke HF_EXT and are instead trying to run the radio on HF_INT.

[Elliott Makin]

Thank you - forgot to initialise the crystal - quite obvious really. Works perfectly now.