I assume that your GNSS device has LTE functionality also because PTCRB only applies to cellular devices.
If it does. Have you had the performance of your antenna measured during the design phase? Passive antenna test measurements will give you some idea, but ideally you should carry out some basic active testing too. Sometimes a device looks good performance wise after passive testing, but when the device is switched on, there many be some noise issues which effect antenna performance.
Its worth carrying out these test first because they are cheaper than the PTCRB test, and if you fail this, you will need to fix the problem and then pay again for a further PTCRB test.
A well designed device with a good performing antenna should pass.
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