Say I have a consumer device that uses a pre-certified WiFi module. As I understand it, radio modules are certified with a fixed set of antenna choices that were included as part of the module's testing.
I understand that using an antenna outside of the approved list is a no-no. I'd like to know specifically why it is a no-no. I have two theories:
TECHNICAL RISK: Using an antenna that was not on the approved list is a technical risk, because you are outside the scope of what has been previously confirmed to pass testing. So you may happen to fail compliance testing because the module performs poorly with this new antenna type. However, you could also get lucky, and end up passing, if the new antenna performs well with the module.
LEGAL ISSUE: Using an antenna that is not on the approved list INVALIDATES the compliance certification of the module. Due to this, the overall consumer device will now be subjected to more vigorous FCC testing, which would have been avoided by using a compliant antenna.
Which of these two theories is the problem with using a non-compliant antenna? Or, is it something else entirely?