https://devzone.nordicsemi.com/f/nordic-q-a/34981/huge-ble-carrier-frequency-driftHi, I have huge BLE carrier frequency drift, which cannot pass FCC requirement. The drift is 256kHz which seems not normal. I&#39;m using 32MHz 10ppm xtal so drift should be few tens of kHz AFAIK. I got images from the test lab as below. en-USTelligent Community 13Fri, 01 Jun 2018 10:35:09 GMThttps://devzone.nordicsemi.com/thread/134328?ContentTypeID=1Fri, 01 Jun 2018 10:35:09 GMT137ad170-7792-4731-bb38-c0d22fbe4515:139cd58c-e89d-409b-b986-c4ea32fc53f9bluera1n<p>Ok. Now I knew it&#39;s offset not drift. Thanks.</p> <p>BTW, CL value of the xtal I&#39;m using is 8pF.</p> <p>So I&#39;m using 12pF according to the calculation you mentioned.</p> <p>I think xtal itself has a problem.</p> <p>Do you think so?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/134299?ContentTypeID=1Fri, 01 Jun 2018 08:48:39 GMT137ad170-7792-4731-bb38-c0d22fbe4515:180474f8-b308-4b1c-9b0f-9134d67ee1e2ketiljo<p>It looks like you&#39;re having an offset, not drift, that&#39;s different.&nbsp;</p> <p>The crystal is probably not loaded correctly. Check the datasheet for the CL value of the crystal and calculate the correct value of the load caps as:&nbsp;</p> <p>Ccap = 2 * CL - 4 pF.</p> <p>For example, a crystal with CL = 12 pF will require 20 pF caps. Round down to 18 pF.</p><div style="clear:both;"></div>